Research Article Tyre Volume and Pressure Effects on Impact...
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Research Article Tyre Volume and Pressure Effects on Impact Attenuation during Mountain Bike Riding Paul W. Macdermid, Matthew C. Miller, Fiona M. Macdermid, and Philip W. Fink Massey University, College of Health, School of Sport & Exercise, Palmerston North 4474, New Zealand Correspondence should be addressed to Paul W. Macdermid; [email protected] Received 19 April 2015; Accepted 22 July 2015 Academic Editor: Chao Tao Copyright © 2015 Paul W. Macdermid et al. is is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Exposure to impacts and vibrations has been shown to be detrimental to cross country mountain bike performance and health. erefore, any strategy aimed at attenuating such exposure is useful to participants and/or industry. e purpose of this study was to assess the influence of tyre size and tyre inflation pressure on exposure to impacts. Participants completed nine trials of a technical section (controlled for initial speed and route taken) including nine separate conditions involving three tyre sizes and three tyre inflation pressures normalised per tyre. Performance was determined by time to negotiate the technical section while triaxial accelerometers recorded accelerations (128Hz) to quantify impact exposure and the subsequent effects on soſt tissue response. Increases in tyre size within the range used improved performance ( < 0.0001) while changes to tyre inflation pressure had no effect ( = 0.6870) on performance. Larger tyre sizes and lower tyre inflation pressures significantly ( < 0.0001) reduced exposure to impacts which could be augmented or negated due to an interaction between tyre size and inflation pressure ( < 0.0001). It is recommended that mountain bikers use larger tyres, inflated to the moderate pressures used within this study, in order to increase performance and reduce the risk of overuse injuries. 1. Introduction Initial studies into the work demand of Olympic format cross country mountain biking (XCO-MTB) identified disassocia- tion of physiological variables (heart rate (HR) and oxygen consumption ( ̇ VO 2 )) with power output [1–4]. is disas- sociation was established through analysis of terrain data, showing that throughout periods of zero propulsive work XCO-MTB athletes are not afforded the same recovery as per riding over smooth surface terrain [5]. Laboratory studies [6, 7] showed that exposure to vibrations increased physiological strain [7] which was associated with a decreased time to exhaustion [6]. Subsequent field based research [8] drew attention to the increased nonpropulsive work component of downhill mountain biking through an increase in muscular contraction of the upper body. is has since been linked to vibration damping plus shock attenuation and is reflected by significant reductions at the lower back and head [9] com- pared to points of contact with the bicycle. e purpose of this is to protect the central nervous system from injury to the spine, spinal cord, or brain [6]. Ultimately, such damping increases motor unit involvement for a given force produc- tion, resulting in a decreased rider economy [10, 11]. Under- standing the interaction between surface terrain and rider economy is important in order to not only increase overall performance but also reduce the risk of overuse injuries. erefore, any strategy with the potential to lessen vibra- tion exposure warrants investigation in order to determine authenticity. Initial work in this area has identified the value of the full suspension bicycle in reducing vibration exposure [12] albeit with negative consequences on performance explained via the increased weight component. However, the international governing organisation of XCO-MTB (UCI) has no rules regarding the wheel size competitors use which could pos- sibly affect vibrations experienced and overall performance [9]. Only one such study has been published at present, dis- covering that increased wheel diameter instigated greater vibration exposure and thus the level of damping required [9]. While the result was unexpected, it could be explained via Hindawi Publishing Corporation Shock and Vibration Volume 2015, Article ID 191075, 10 pages http://dx.doi.org/10.1155/2015/191075
Transcript of Research Article Tyre Volume and Pressure Effects on Impact...
Research ArticleTyre Volume and Pressure Effects on Impact Attenuation duringMountain Bike Riding
Paul W Macdermid Matthew C Miller Fiona M Macdermid and Philip W Fink
Massey University College of Health School of Sport amp Exercise Palmerston North 4474 New Zealand
Correspondence should be addressed to Paul W Macdermid pwmacdermidmasseyacnz
Received 19 April 2015 Accepted 22 July 2015
Academic Editor Chao Tao
Copyright copy 2015 Paul W Macdermid et al This is an open access article distributed under the Creative Commons AttributionLicense which permits unrestricted use distribution and reproduction in any medium provided the original work is properlycited
Exposure to impacts and vibrations has been shown to be detrimental to cross country mountain bike performance and healthTherefore any strategy aimed at attenuating such exposure is useful to participants andor industry The purpose of this studywas to assess the influence of tyre size and tyre inflation pressure on exposure to impacts Participants completed nine trials of atechnical section (controlled for initial speed and route taken) including nine separate conditions involving three tyre sizes and threetyre inflation pressures normalised per tyre Performance was determined by time to negotiate the technical section while triaxialaccelerometers recorded accelerations (128Hz) to quantify impact exposure and the subsequent effects on soft tissue responseIncreases in tyre size within the range used improved performance (119875 lt 00001) while changes to tyre inflation pressure had noeffect (119875 = 06870) on performance Larger tyre sizes and lower tyre inflation pressures significantly (119875 lt 00001) reduced exposureto impacts which could be augmented or negated due to an interaction between tyre size and inflation pressure (119875 lt 00001) It isrecommended that mountain bikers use larger tyres inflated to the moderate pressures used within this study in order to increaseperformance and reduce the risk of overuse injuries
1 Introduction
Initial studies into the work demand of Olympic format crosscountry mountain biking (XCO-MTB) identified disassocia-tion of physiological variables (heart rate (HR) and oxygenconsumption (VO
2)) with power output [1ndash4] This disas-
sociation was established through analysis of terrain datashowing that throughout periods of zero propulsive workXCO-MTB athletes are not afforded the same recovery as perriding over smooth surface terrain [5] Laboratory studies [67] showed that exposure to vibrations increased physiologicalstrain [7] which was associated with a decreased time toexhaustion [6] Subsequent field based research [8] drewattention to the increased nonpropulsive work component ofdownhill mountain biking through an increase in muscularcontraction of the upper body This has since been linked tovibration damping plus shock attenuation and is reflected bysignificant reductions at the lower back and head [9] com-pared to points of contact with the bicycleThepurpose of thisis to protect the central nervous system from injury to
the spine spinal cord or brain [6] Ultimately such dampingincreases motor unit involvement for a given force produc-tion resulting in a decreased rider economy [10 11] Under-standing the interaction between surface terrain and ridereconomy is important in order to not only increase overallperformance but also reduce the risk of overuse injuriesTherefore any strategy with the potential to lessen vibra-tion exposure warrants investigation in order to determineauthenticity
Initial work in this area has identified the value of the fullsuspension bicycle in reducing vibration exposure [12] albeitwith negative consequences on performance explained viathe increased weight component However the internationalgoverning organisation of XCO-MTB (UCI) has no rulesregarding the wheel size competitors use which could pos-sibly affect vibrations experienced and overall performance[9] Only one such study has been published at present dis-covering that increased wheel diameter instigated greatervibration exposure and thus the level of damping required [9]While the result was unexpected it could be explained via
Hindawi Publishing CorporationShock and VibrationVolume 2015 Article ID 191075 10 pageshttpdxdoiorg1011552015191075
2 Shock and Vibration
Table 1 Characteristics of the tyres used during the study
Tyre model Σ119879wt (g) ISOETRTO (mm) Est 119879vol (cm3) Manufacturer technology TPI Recommended tyre pressure (psi)
CycloXKing 760 35ndash622 1980 Performance 3180 56ndash85XKing 1380 55ndash622 5050 Performance 3180 50ndash65XKing 1470 60ndash622 6060 Performance 3180 50ndash65
an increase in the speed travelled per work done leadingto the positive outcome of improved performance over aXCO-MTB lap inclusive of additional rotational weight [9]Despite the fact that performance improved the increasedvibration exposure is still an issue with respect to potentialoveruse injuries and further performance enhancementSupplementary to the wheel size increase the tyre sizecombinedwith its inflated air pressure (psi) could assist recre-ational and competitive off-road cyclists to achieve a morecomfortable experience Work investigating related issuesin farm machinery operation have shown that increasingtyre inflation pressures were capable of considerable changes(up to 75) in estimated vibration exposure [13] This isfurther supported in wheelchair users [14] Yet paradoxicallyreduced tyre inflation pressures increased rolling resistanceby 35 amongst wheelchair users [14 15] Quantifying suchrelationships in terms of comfort and performance duringmountain biking is important to understand
The objective of this study was therefore to quantifythe influence of tyre size and inflation pressure on impactattenuation transmitted from surface terrain to bicycle andthe cyclist during the negotiation of a technical componentsimilar to that experienced during XCO-MTB racing It washypothesised that larger tyre sizes would lower the level ofimpact exposure experienced at the point of contact betweenbicycle and body while higher tyre inflation pressures withintyre sizes would increase the level of impact exposureAdditionally the benefit of tyre size could be negated throughhigh tyre pressures
2 Method
Twelve experienced mountain bikers (National (NZ) levelcross-country athletes) consented in accordance with theUniversity Human Ethics Committee to take part in thisstudy All participants used the same bicycle (GT Zaskar elite2910158401015840 Full Suspension Optimized Force Constructed CarbonUSA) adjusted to personal requirements prior to the trialand thus controlling posture The bicycle was fitted with afront (Rockshox Recon 100mm Solo Air USA) and rearsuspension (Fox Float CTD USA) system set as per themanufacturers recommendations for specific body weightsHowever both front suspension and rear suspension werethen switched to lock-outmode in order to allownomechani-cal damping as a result of suspensionTherefore any effect onacceleration measured would be as a result of the interven-tion(s)
21 Field Test Trial The experimental protocol involved thenegotiation of two flights of eight steps (dimension 26 times13 cm) equal throughout with the two flights separated by
A B
C
486m26 cm 26 cm
13 cm 13 cm
times8 times8
Figure 1 Pictorial representation of the experimental protocolwhere A signifies the start point with the front wheel B indicates thepoint at which timing commenced and C is where timing ceasedThe distance from A-B was dependent on the specific tyre rollout(see Table 1)
a distance of 486m (Figure 1) This obstacle was chosen inorder to simulate a moderatetypical technical downhill sec-tion on a cross country mountain bike course while beingable to control participant run up and the route taken It wasfelt that this aspect would be uncontrollable whilst riding across country mountain bike trail
Determination of the start position distance from the firststep was equal to wheel roll-out distance for specific tyre sizes(Table 1) This permitted participants one complete pedalstroke which started with the preferred lead foot at 45∘enabling them to hit point B (Figure 1) in the ready position(preferred foot and pedal at sim90∘ angle) just prior to negoti-ation of the steps The distance (A-B Figure 1) was equalledat the bottom of the second flight of stairs to mark the finish(C Figure 1) and allow the whole bicycle to have negotiatedthe second flight of steps Front chainring (36 tooth) and rearcassette cog (14 tooth) were standardised for all participantsthroughout the study
Participants completed six conditions including threedifferent tyres of the same tread pattern and constructionbut differing in size and weight (Table 1) For each tyre threetyre inflation pressures were selected based on the standard(22 Xking) XCO-MTB tyre and the typical inflation pressurevalues used by expert XCO-MTB cyclists and cited elsewhere[16]The standardised tyre inflation pressure value (tyre infla-tion pressure (moderate) for Xking 22) was 03 psi per totalweight (Bike + fully clothed and helmeted cyclist)
In order to calculate a proportional value for the otherconditions (nontypical XCO-MTB tyres including cycloXK-ing and Xking 24 Table 1) a ratio of estimated tyre volumebetween conditions was used This involved factorising thestandardised value for the 22 Xking tyre by 1629 and 0868
Shock and Vibration 3
(a)
(b)
Figure 2 Pictorial image of the two main tyres ((a) cyclocross and(b) mountain bike)
for the cycloXKing and Xking 24 tyres respectively Esti-mated tyre volume (Est119879vol) was based on ISOETRTOmea-surements [17] and Pappusrsquos centroid theorem for calculatingvolume of a torus (cm3) [16] From these values further fac-torising took place to establish a normalised and proportionallow (0666lowast) and high (1333lowast) tyre inflation pressure for alltyres Comparison of the three tyres and the inflation pres-sures can be seen in Figures 2 and 3
22 Outcome Measures Wireless triaxial accelerometersmagnetometers and gyroscopes with a reported accuracy00012msdots2 sdotradicHzminus1 (Emerald APDMORUSA)were used ina synchronised data-logging mode to measure accelerationsas previously reported during XCO-MTB [9]Through use ofa trigger to switch on the accelerometers performance time(s) was also recorded from point B-C Figure 1 The accelero-meters were placed on the lower left arm (frontal distal posi-tion) left lower leg (frontal distal position) seat post (within10 cm of the saddle-rider contact area) lumbar region of thelower back and medial forehead [9] All data was sampledat 128Hz logged to a standard personal computer convertedto a hierarchal data format file (h5) and processed usingMATLAB R2014a All data were analysed for total (119909- 119910-and 119911-axis) vertical (119911-axis) and horizontal (119909- and 119910-axis)accelerations Root mean squares (RMS) of the accelerationswere calculated to quantify overall effect of conditions whilespectral analysis was performed (Fast Fourier Transform)to determine maximum magnitude (m2sdotsminus4) maximum fre-quency (Hz) and quantification ofmovements as low (lt5Hz)and high (gt5Hz) power
23 Statistical Analyses Descriptive (mean plusmn SD) were cal-culated for all variables measured during each condition
Two-way repeated analysis of variance (ANOVA) withtwo within-subject variables (tyre size lowast tyre inflation pres-sure) was used to test differences in time to complete the pro-tocol with a Tukeyrsquos post hoc comparisonwithin tyre inflationpressure for each tyre
Low psi Moderate psi High psi0
10
20
30
CX22
Tyre pressure categorisation
24
Tyre
pre
ssur
e (ps
i)
Figure 3 Comparison of the three tyres and the respective inflationpressures used
Acceleration data comparisons were made via univariateanalysis of variance (three-way ANOVA) including within-subject variables tyre size tyre inflation pressure and accel-erometer location tested for main effects and interactions(tyre size lowast tyre inflation pressure lowast accelerometer locationtyre sizelowast tyre inflation pressure tyre sizelowast acceleration loca-tion and tyre inflation pressure lowast accelerometer location)Where significant difference was found the main effect wasanalysed using Bonferroni post hoc testing pairwise compar-ison
All statistical analyses were performed using IBM SPSSstatistics 20 significance set at 119875 lt 005
3 Results
31 Performance Analysis Participants completed a simu-lated technical component typical of the impacts associatedwith a XCO-MTB course [9]
Two-way ANOVA identified significant main effects fortyre size (119865
(233)= 4446 119875 lt 00001) but not tyre inflation
pressures within tyres (119865(233)= 1407 119875 = 02591) for time
to complete the trial (Figure 4) There was no interaction(119865(466)= 05676119875 = 06870) between tyre size and tyre infla-
tion pressure
32 Acceleration Data Analysis Three-way ANOVA of totalacceleration amplitude (RMS) showed that there was a signif-icant main effect for tyre size (119865
(233)= 72847 119875 lt 00001)
tyre inflation pressure (119865(233)= 38230 119875 lt 00001) and
accelerometer locations (119865(566)= 72847 119875 lt 00001) plus
an interaction (119865(9132)= 6114 119875 = 00001) between tyre size
and tyre inflation pressures (Figures 5(a)ndash5(c)) Key findingsfrom post hoc analysis showed differences for tyre size (119875 lt00001) between the cycloXKing (cx) and 22 XKing (95CI 0907ndash2102) cycloXKing and 24 XKing (95 CI 2406ndash3601) and 22 and 24 XKing (95 CI 0901ndash2096) tyre
4 Shock and Vibration
Low High0
1
2
3
4
5
ModerateNormalized tyre pressure
Tim
e (s)
CX (35mm)22 (55mm)24 (60mm)
lowastlowastlowastlowast
++++++++ ++++
+++++++ +++nabla
Figure 4 Mean plusmn SD for performance time (s) over the trialprotocol (Figure 1) lowastlowastlowastlowast(119875 lt 00001) main effect of tyre post hocdifferences when comparing tyres for within-tyre inflation pressureswhen compared to CX ++++(119875 lt 00001) +++(119875 lt 0001) and 22nabla(119875 lt 005)
inflation pressure (119875 lt 005) between pressure low andmoderate (95 CI minus1261ndashminus0066) low and high (95 CIminus2724ndashminus1529) and moderate and high (95 CI minus2060ndashminus0866) Multiple comparisons between the accelerometerlocations were significantly different (119875 lt 00001) except inthe case of the handlebar and seat post (119875 = 0824 95 CIminus0360ndash1714) and the lower back and forehead (119875 = 009295 CI minus0069ndash2005)
Significant main effects for vertical acceleration ampli-tude (RMS) for tyre size (119865
(233)= 16010 119875 lt 00001) tyre
inflation pressure (119865(233)= 17319 119875 lt 00001) and accel-
erometer location (119865(566)= 26543 119875 lt 00001) were found
(Figures 5(d)ndash5(f)) There were significant interactions bet-ween tyre size and accelerometer location (119865
(799)= 4657
119875 lt 00001) and tyre inflation pressure and accelerometerlocation (119865
(799)= 4253 119875 lt 00001) Post hoc analysis
showed significant differences (119875 lt 00001) for tyre sizebetween cycloXKing and 22 XKing (95 CI 0360ndash1163)and cycloXKing and 24 XKing (95 CI 0466ndash1270)normalised tyre inflation pressure between low and high(95 CI minus1347ndashminus05440) and moderate and high (95 CIminus01666ndash0637) Multiple comparisons between accelerome-ter locations were significantly different (119875 lt 001) except inthe case of the handlebar and wrist (119875 = 1000) and lowerback and forehead (119875 = 1000)
Horizontal accelerations (Figures 5(g)ndash5(i)) showedmaineffects for tyre size (119865
(233)= 35895 119875 lt 00001) tyre infla-
tion pressure (119865(233)= 10460 119875 lt 00001) and accelero-
meter location (119865(566)= 1548645 119875 lt 00001) with inter-
actions between tyre size lowast tyre inflation pressure (119865(466)=
3111 119875 = 00150) tyre size lowast accelerometer location(119865(799)= 10116 119875 lt 00001) and tyre inflation pressure lowast
accelerometer location (119865(799)= 1866 119875 = 00470) Post
hoc analysis identified differences between all tyre sizes (119875 lt001) between tyre inflation pressures low and high (119875 lt00001) and moderate and high (119875 = 00109) and betweenall accelerometer locations (119875 lt 005)
Three-way ANOVA of spectral analysis maximum fre-quency (Table 2) data provided a significant interactionbetween tyre size and accelerometer location (119865
(799)= 6700
119875 lt 00001) with a main effect of tyre size (119865(233)= 12553
119875 lt 00001) and accelerometer location (119865(566)= 51011 119875 lt
00001) Post hoc analysis identified differences between tyresizes cycloXKing and 22 XKing (95 CI minus02865ndashminus07662)and cycloXKing and 24 XKing (95 CI minus03017ndashminus00919)Data for maximummagnitude (Table 3) identified significantmain effects for tyre size (119865
(233)= 34420 119875 lt 00001)
tyre inflation pressure (119865(233)= 22864 119875 lt 00001) and
acceleration position (119865(566)= 3336605 119875 lt 00001) with
interactions between tyre size lowast accelerometer position(119865(799)= 10852 119875 lt 00001) and tyre inflation pressure lowast
accelerometer location (119865(799)= 4271 119875 lt 00001) Post hoc
analysis showed differences between tyre sizes occurred forcycloXKing and 2210158401015840 Xking (119875 = 00050) cycloXKing and2410158401015840 XKing (119875 lt 00001) and 2210158401015840 XKing and 2410158401015840 XKing(119875 lt 00001) tyre inflation pressure differences occurredbetween low and moderate (119875 = 0026) low and high(119875 lt 00001) and moderate and high (119875 = 00002) whiledifferences between all accelerometer positions (119875 lt 00500)except lower back and forehead (119875 gt 00500) occurred
Power data separated for low (lt5Hz) frequency (Table 4)identified significantmain effects for tyre size (119865
(233)= 5157
119875 = 00060) and accelerometer position (119865(566)= 1855902
119875 lt 00001) interactions between tyre size and accelerometerposition (119865
(799)= 1990 119875 = 00320) and tyre inflation pres-
sure and accelerometer position (119865(799)= 1998 119875 = 00310)
Post hoc differences for tyre size between cycloXKing and2210158401015840 XKing (95 CI minus04853ndashminus00693 119875 = 00040) werepresent and all accelerometer positions except the handlebarand seat post (119875 = 06330) High (gt5Hz) frequency (Table 4)showed significant main effects for tyre inflation pressure(119865(233)= 17516 119875 lt 00001) and accelerometer position
(119865(566)= 5190764 119875 lt 00001) with interactions for tyre
sizelowast tyre inflation pressure (119865(466)= 4210119875 = 00020) tyre
size lowast accelerometer position (119865(799)= 9575 119875 = 00070)
and tyre inflation pressure lowast accelerometer position (119865(799)=
2091 119875 = 00230) Post hoc analysis identified differenceswithin the tyre inflation factor between low andhigh pressure(95 CI minus15404ndashminus06302 119875 lt 00001) and moderate andhigh pressure (95 CI minus12441ndashminus03339 119875 lt 00001) Allaccelerometer positions were different (119875 lt 00001) exceptin the case of the handlebar and wrist (119875 = 07560) and thelower back and head (119875 = 10000)
4 Discussion
The aim of this study was to quantify the influence of tyresize and the normalised tyre inflation pressure on exposureto impacts and their interactions typical of that experiencedwhilst riding on a cross countrymountain bike trailThemainfindings were as follows (a) increases in tyre size led to
Shock and Vibration 5
Han
dleb
ar
Wris
t
Ank
le
Seat
pos
t
Lum
bar
Hea
d
Han
dleb
ar
Wris
t
Ank
le
Seat
pos
t
Lum
bar
Hea
d
Han
dleb
ar
Wris
t
Ank
le
Seat
pos
t
Lum
bar
Hea
d
Han
dleb
ar
Wris
t
Ank
le
Seat
pos
t
Lum
bar
Hea
d
Han
dleb
ar
Wris
t
Ank
le
Seat
pos
t
Lum
bar
Hea
d
Han
dleb
ar
Wris
t
Ank
le
Seat
pos
t
Lum
bar
Hea
d
Han
dleb
ar
Wris
t
Ank
le
Seat
pos
t
Lum
bar
Hea
d
Han
dleb
ar
Wris
t
Ank
le
Seat
pos
t
Lum
bar
Hea
d
Han
dleb
ar
Wris
t
Ank
le
Seat
pos
t
Lum
bar
Hea
d
(a) (b) (c)
(d) (e) (f)
(g) (h) (i)Normalised tyre inflation pressure Normalised tyre inflation pressure Normalised tyre inflation pressure
Low Moderate High
Acce
lera
tion
axis
Acce
lera
tion
axis
Acce
lera
tion
axis
Hor
izon
tal
Vert
ical
Tota
l
0102030405060
Acce
lera
tion
(mmiddotsminus
2)
0102030405060
Acce
lera
tion
(mmiddotsminus
2)
0102030405060
Acce
lera
tion
(mmiddotsminus
2)
0102030405060
Acce
lera
tion
(mmiddotsminus
2)
0102030405060
Acce
lera
tion
(mmiddotsminus
2)
0102030405060
Acce
lera
tion
(mmiddotsminus
2)
0102030405060
Acce
lera
tion
(mmiddotsminus
2)
0102030405060
Acce
lera
tion
(mmiddotsminus
2)
0102030405060
Acce
lera
tion
(mmiddotsminus
2)
Accelerometer position Accelerometer position Accelerometer position
poundpoundpoundpoundlowastlowast $$$$ otimesotimesotimesotimes nablanablanablanabla emptyemptyemptyempty
poundpoundpoundpound $$$$ otimesotimesotimesotimes nablanablanablanabla emptyemptyemptyempty
lowastlowastlowastlowast otimesotimesotimesotimes nablanablanablanabla emptyemptyemptyempty
Figure 5 Comparison between tyres (CycloXKing (black bar) 22 XKing (gray bar) and 24 XKing (white bar)) and three normalisedtyre inflation pressures characterised as low (1) normal (2) and high (3) for (a)ndash(c) Total accelerations (d)ndash(f) Vertical accelerations (g)ndash(i) Horizontal accelerations where lowast refers to the interaction for tyre size lowast tyre pressure (lowastlowastlowastlowast119875 lt 00001 lowastlowast119875 lt 001) $ refers to theinteraction for tyre sizelowast accelerometer location ($$$$119875 lt 00001) m refers to the interaction for tyre pressurelowast accelerometer location (mmmm119875 lt00001) otimesotimesotimesotimes(119875 lt 00001)main effect of tyre size OslashOslashOslashOslash(119875 lt 00001)main effect of tyre pressure nablanablanablanabla(119875 lt 00001)main effect of accelerometerlocation
positive effects on performance compared to tyre inflationpressure when riding down rough terrain (b) increases intyre size decrease the level of impact exposure experienced atpoint of contact(s) with the bicycle and thus reduce nonprop-ulsive work load (c) increased tyre inflation pressure intensi-fies exposure to acceleration exposure
Increased exposure to impacts and vibrations associatedwith forwards momentum of an off-road cyclist are linked toincreased nonpropulsive work [8] decreased efficiency [11]and performance [6 7] The reduction of this nonpropulsivework is thus potentially important with regard to competitiveperformance and theminimisation of overuse injury risk [18]
6 Shock and Vibration
Table2MeanplusmnSD
form
axim
umfre
quency
(Hz)of
acceleratio
nsdu
ringthetria
lseparatedfora
ccelerom
eter
locatio
ntyre
sizeandtyre
inflatio
npressure
Accelerometer
position
Cyclo
XKingtyreclubsclubsclubsclubs
2210158401015840XK
ingtyre
2410158401015840XK
ingtyre
3-way
ANOVA
LowPS
IMod
PSI
HighPS
ILo
wPS
IMod
PSI
HighPS
ILo
wPS
IMod
PSI
HighPS
IHandlebar
05284plusmn0049
05084plusmn004
605099plusmn006
005659plusmn0043
05632plusmn0036
05526plusmn0036
05781plusmn0029
060
03plusmn0055
05565plusmn0032
Tyrelowastlowastlowastlowast
PSIN
S
ALoclowastlowastlowastlowast
TyrelowastALoclowastlowastlowastlowast
Wris
t05284plusmn0049
05084plusmn004
605099plusmn006
005659plusmn0043
05632plusmn0037
05526plusmn0037
05781plusmn0029
060
03plusmn0055
05787plusmn0076
Ank
le05284plusmn0049
05084plusmn004
605099plusmn006
005659plusmn0043
05632plusmn0037
05526plusmn0036
05781plusmn0029
060
03plusmn0055
05787plusmn0032
Seatpo
st05284plusmn0049
05088plusmn0036
05099plusmn0036
05659plusmn0043
05654plusmn0036
05539plusmn0036
05781plusmn0029
060
03plusmn0055
05565plusmn0032
Lumbarotimesotimesotimesotimes
08372plusmn0760
08165plusmn0756
05345plusmn0123
13076plusmn1168
18315plusmn10
3416
682plusmn14
5320180plusmn14
2113
681plusmn
1034
14722plusmn1166
Forehead
05749plusmn0259
05088plusmn004
605099plusmn006
006518plusmn0284
05202plusmn0123
05098plusmn0121
05749plusmn0030
060
49plusmn0051
05117plusmn0117
Tyre(ty
resiz
e)PSI
(tyreinflatio
npressure)andALoc
(accelerom
eter
position)
refertothem
aineffectfor
maxim
umfre
quencyTyrelowast
ALoc
refersto
thetwo-way
interactionbetweentyresiz
eand
accelerometer
position
NSdeno
tesa
nonsignificanteffect(119875gt0005)lowastlowastlowastlowast(119875lt00001)clubsclubsclubsclubssig
nifiesa
postho
cdifference
(119875lt00001)for
tyre
sizew
hencomparin
gcyclo
XKingto
both
2210158401015840and2410158401015840XK
ingtyreotimesotimesotimesotimes
signifiesa
postho
cdifference
(119875lt00001)for
accelerometer
positionwhencomparedto
allother
accelerometer
positions
Shock and Vibration 7
Table3MeanplusmnSD
form
axim
ummagnitude
(g2 )of
acceleratio
nsdu
ringthetria
lseparatedfora
ccelerom
eter
locatio
ntyre
sizeandtyre
inflatio
npressure
Accelerometer
position
Cyclo
XKingtyre
2210158401015840XK
ingtyreclubsclubs
2410158401015840XK
ingtyreclubsclubsclubsclubs
3-way
ANOVA
LowPS
IMod
PSIoplus
HighPS
Ioplusoplus
LowPS
IMod
PSIoplus
HighPS
Ioplusoplus
LowPS
IMod
PSIoplus
HighPS
Ioplusoplus
Handlebar
96649plusmn0483
98169plusmn0837
99169plusmn0394
91121plusmn
0572
95915plusmn040
799
974plusmn0523
860
00plusmn076591403plusmn0489
96618plusmn0356
Tyrelowastlowastlowastlowast
PSIlowastlowastlowastlowast
ALoclowastlowastlowastlowast
TyrelowastALoclowastlowastlowastlowast
PSIlowast
ALoclowastlowastlowastlowast
Wris
t89805plusmn0969
92501plusmn
1016
93962plusmn0698
84191plusmn0744
86780plusmn0770
91158plusmn0944
80720plusmn0897
88992plusmn10
9285109plusmn0374
Ank
le104872plusmn0882106966plusmn12
44108250plusmn0903
90277plusmn13
9991
134plusmn0990
1015
14plusmn0970
86496plusmn14
3174
320plusmn0793
95862plusmn1127
Seatpo
st85581plusmn0596
88560plusmn10
0988657plusmn0831
85843plusmn10
9791
929plusmn0997
95898plusmn0936
81989plusmn14
0789681plusmn13
7592
576plusmn0977
Lumbar
09245plusmn0201
10165plusmn0315
09747plusmn0279
09550plusmn0198
09176plusmn0129
09810plusmn0169
08461plusmn0094
09134plusmn0124
09347plusmn0138
Forehead
12333plusmn0265
11829plusmn0106
12301plusmn
0220
10693plusmn
0184
11935plusmn0218
11763plusmn0147
11001plusmn
0150
10876plusmn0210
11283plusmn0244
Tyre(ty
resiz
e)PSI
(tyreinflatio
npressure)andALoc
(accelerom
eter
position)
refertothem
aineffectfor
maxim
umfre
quencyTyrelowast
ALoc
refersto
thetwo-way
interactionbetweentyresiz
eand
accelerometer
position
NSdeno
tesa
nonsignificanteffect(119875gt0005)lowastlowastlowastlowast(119875lt00001)clubsclubsclubsclubssig
nifiesa
postho
cdifference
(119875lt00001)a
ndclubsclubs(119875lt001)for
tyre
sizew
hencomparedto
cyclo
XKingtyreotimesotimesotimesotimessig
nifiesa
postho
cdifference
(119875lt00001)otimesandoplus(119875lt005)for
tyre
inflatio
npressure
whencomparedto
LowPS
Iandoplusoplus(119875lt0001)com
paredto
Mod
PSI
8 Shock and Vibration
Table4MeanplusmnSD
form
ovem
entsseparatedforlow
(lt5H
z)andhigh
(gt5H
z)po
wer
Accelerometer
position
Cyclo
Xkingtyre
2210158401015840XK
ingtyreclubsclubs
2410158401015840XK
ingtyre
3-way
ANOVA
LowPS
IMod
PSI
HighPS
ILo
wPS
IMod
PSIoplusoplusoplusoplus
HighPS
ILo
wPS
IMod
PSI
HighPS
Iotimesotimesotimesotimes
Lowpo
wer
hand
lebar
76020plusmn0372
73377plusmn0730
73461plusmn
0722
79999plusmn0706
80373plusmn0601
78545plusmn066
777
180plusmn0535
81915plusmn0921
73545plusmn0496
Tyrelowastlowastlowast
ALoclowastlowastlowastlowast
TyrelowastALoclowast
PSIlowast
ALoclowast
Wris
t1110
12plusmn14
331110
16plusmn0798
108242plusmn0665112274plusmn0783
113173plusmn0791
111153plusmn0940
107093plusmn0831
112719plusmn1111
1117
09plusmn14
81Ank
le88034plusmn12
8687661plusmn15
7491
143plusmn15
0485389plusmn15
5685304plusmn13
6793
778plusmn12
2886588plusmn18
5177
914plusmn0866
89735plusmn15
55Seatpo
st70
221plusmn
0892
69096plusmn1130
69559plusmn1100
77862plusmn0844
7740
8plusmn0802
76287plusmn0682
74695plusmn0979
81789plusmn15
9575
053plusmn0870
Lumbar
22323plusmn0428
22711plusmn0431
22088plusmn0555
23851plusmn0393
23896plusmn0385
24398plusmn0512
21917plusmn0240
21500plusmn0199
22178plusmn0242
Forehead
16805plusmn0125
15723plusmn0205
16235plusmn0241
17659plusmn0225
17505plusmn0263
15788plusmn0168
17763plusmn046
016
319plusmn0482
16620plusmn0461
Highpo
wer
hand
lebar
309527plusmn10
84316942plusmn2200
319095plusmn1144
313476plusmn16
95325003plusmn2085328681plusmn
1642
309170plusmn2816
325744plusmn2808338956plusmn2025PS
Ilowastlowastlowastlowast
ALoclowastlowastlowastlowast
TyrelowastPS
Ilowastlowast
TyrelowastALoclowastlowast
PSIlowast
ALoclowast
Wris
t310326plusmn17
613118
62plusmn19
44319101plusmn
1745
308851plusmn
1646
307399plusmn15
88324736plusmn18
583110
31plusmn16
343252
17plusmn2201
320763plusmn10
01Ank
le320164plusmn2753
307261plusmn
1813
308363plusmn19
35294291plusmn
1562
297999plusmn19
623119
27plusmn1746
299579plusmn4112
287204plusmn1748
3252
10plusmn2184
Seatpo
st343183plusmn2782
339910plusmn2618
3374
90plusmn19
463114
56plusmn2294324106plusmn204
8339546plusmn19
09306605plusmn4610324129plusmn356434364
6plusmn2565
Lumbar
540
80plusmn12
6055831plusmn0971
544
96plusmn1139
53255plusmn13
3454598plusmn12
1254818plusmn12
1248842plusmn0432
46912plusmn0481
53320plusmn0485
Forehead
55814plusmn13
9762502plusmn0620
58694plusmn0998
49398plusmn10
8350786plusmn14
2353796plusmn1525
57876plusmn1741
46845plusmn0808
59633plusmn15
70Where
tyre
(tyre
size)P
SI(ty
reinflatio
npressure)andALoc
(accele
rometer
locatio
n)refertothem
aineffectfor
power
band
Tyrelowast
ALoc
refersto
thetwo-way
interactionbetweentyre
sizea
ndaccelerometer
locatio
nlowastdeno
tessignificance
(119875lt005)lowastlowast(119875lt001)lowastlowastlowast(119875lt0001)lowastlowastlowastlowast(119875lt00001)clubsclubssig
nifiesa
postho
cdifference
(119875lt001)for
lowpo
wer
whencomparedto
cyclo
XKingtyre
sizeotimesotimesotimesotimessig
nifiesa
postho
cdifference
(119875lt00001)for
tyre
inflatio
npressure
whencomparedto
LowPS
Iandoplusoplusoplusoplus(119875lt00001)com
paredto
HighPS
I
Shock and Vibration 9
In the first instance Figure 4 identifies the highly signifi-cant (119875 lt 00001) effect of tyre size on performance timewithregard to normalised tyre inflation pressures This is furtherexacerbated considering the typical tyre inflation pressure(moderate Figure 3) used by competitive XCO-MTB athletes[16] At this pressure post hoc analysis identified differencesbetween 2210158401015840 and 2410158401015840 XKing tyres suggesting that tyre sizecould have considerable effect on performance
While difficult to glean conclusive data regarding overallXCO-MTB performance from such a small downhill com-ponent of performance as collected in this study it is worthnoting that previous research has linked decreased vibrationexposure to increased efficiency [10 11] As such the attenu-ation of accelerations experienced (Figure 5 and Tables 3 and4) at the point of contact between human and bicycle (han-dlebar and seat post) as a result of increased tyre size couldtheoretically be connected to overall performance duringcomplete race distance This obviously assumes that the dec-rease in nonpropulsive work would reduce muscular andcognitive fatigue and consequentially increase performanceHowever it is acknowledged that a complete XCO-MTB raceentails a variety of surfaces and terrains where themajority oftime is spent cycling uphill on smoother surfaces that mightactually suit a smaller higher pressure tyre As such futureresearch is needed to explore this aspect
On the other hand tyre inflation pressure does not seemto influence performance in this experiment (Figure 4) eventhough an increase in accelerations in all axes (Figure 5)related to an increase in magnitude (Table 3) rather than fre-quency (Table 2) was apparent While interesting the tran-sient nature of the protocol used cannot corroborate thelong term effects that racing for ge90mins with the observedincreases in magnitude would have on accumulated muscu-lar fatigue Based on previous laboratorywork [6 19] it is beli-eved that XCO-MTB performance would be compromisedover a complete race distance but requires confirmation
Similar to previous work on the transference of acceler-ations during XCO-MTB [9] the data presented here showsthat both the bicycle and the soft tissue are dissipating energy[20 21] from the interaction of bicycle with surface terrainimplying a reduced nonpropulsive work component of XCO-MTB as a result of increased tyre size This is supportedthrough two-way interactions between both tyre size lowast accel-erometer position and tyre inflation pressure lowast accelero-meter location for total vertical and horizontal accelera-tions (Figure 5) magnitude (Table 3) and low-high powerdistribution (Table 4) As such the reduction in measuresassociated with acceleration exposure reported previouslydecreased at the point of interaction with the bicycle withan increase in tyre size Importantly this was accompaniedby reductions at the soft tissue sites implying a reduced non-propulsive work component of XCO-MTB as a result ofincreased tyre size Alternatively increases in tyre inflationpressure have the opposite and negative effect by increasingrider exposure to accelerations at the point of interface withbicycle and thus increase the non-propulsive componentAdditionally the controlled nature of this protocol mayenable participants to alter body position or riding style
dependent on tyre chracteristics not afforded during a racingsituation
5 Conclusion
This study set out to quantify the influence of tyre size andnormalised tyre inflation pressure on exposure to impactstypical to cross country mountain bike riding It was foundthat the larger the tyre size within the range tested thelower the level of impact exposure experienced at the pointof contact between bicycle and body This reduction meantparticipants performed less non-propulsive muscular workand performed better when compared to a smaller tyre of thesame construction and tread pattern Contrariwise highertyre inflation pressures were associated with an increase inthe level of impact exposure and thus greater soft tissue workin order to attenuate the larger impacts In addition it wasshown that increased tyre inflation pressure could interactnegatively with tyre size while increased tyre size couldinteract positively with tyre inflation pressure As such theeffects of reduced exposure need to be assessed with regardsto longer periods of time such as experienced in a mountainbike race or recreational ride
6 Practical Application
It is recommended that participants (recreational and com-petitive) use a higher volume tyre over any smaller alternativewithin the range tested here In doing so it is suggested thatparticipants could improve performance and likely reducethe risk of overuse injuries or increase the time spent ridingfor the same risk(s)
It is important to note that two-way interactions betweentyre size and tyre inflation pressures suggest that the benefitsof riding with a bigger tyre could be negated through the useof high tyre inflation pressure Conversely the use of lowertyre inflation pressures in smaller tyres could reduce exposurebut must come with a warning of increased unreliability interms of punctures and de-beading from the wheel rim
7 Future Research
The findings of this study must now be verified over a com-plete XCO-MTB race lap consisting of a variety of terrainsto enable whole performance analysis and terrain specificsection performance analysis
Conflict of Interests
The authors declare that there is no conflict of interestsregarding the publication of this paper
References
[1] H THurst and S Atkins ldquoPower output of field-based downhillmountain bikingrdquo Journal of Sports Sciences vol 24 no 10 pp1047ndash1053 2006
[2] F M Impellizzeri and S M Marcora ldquoThe physiology ofmountain bikingrdquo SportsMedicine vol 37 no 1 pp 59ndash71 2007
10 Shock and Vibration
[3] P W Macdermid and S Stannard ldquoMechanical work andphysiological responses to simulated cross country mountainbike racingrdquo Journal of Sports Sciences vol 30 no 14 pp 1491ndash1501 2012
[4] B Stapelfeldt A Schwirtz Y O Schumacher and M Hille-brecht ldquoWorkload demands in mountain bike racingrdquo Interna-tional Journal of Sports Medicine vol 25 no 4 pp 294ndash3002004
[5] P Macdermid P Fink and S Stannard ldquoThe effects of vibra-tions experienced during road vs off-road cyclingrdquo Interna-tional Journal of Sports Medicine 2015
[6] B Samuelson L Jorfeldt and B Ahlborg ldquoInfluence of vibra-tion on endurance of maximal isometric contractionrdquo ClinicalPhysiology vol 9 no 1 pp 21ndash25 1989
[7] J Titlestad A Fairlie-Clarke M Davie A Whittaker and SGrant ldquoExperimental evaluation of mountain bike suspensionsystemsrdquo Acta Polytechnica vol 43 no 5 2003
[8] H T Hurst M Swaren K Hebert-Losier et al ldquoInfluenceof course type on upper body muscle activity in elite Cross-Country andDownhillmountain bikers during offRoadDown-hill Cyclingrdquo Journal of Science and Cycling vol 1 no 2 pp 2ndash92012
[9] P W Macdermid P W Fink and S R Stannard ldquoTransferenceof 3D accelerations during cross country mountain bikingrdquoJournal of Biomechanics vol 47 no 8 pp 1829ndash1837 2014
[10] P W Macdermid P W Fink and S R Stannard ldquoThe effectsof vibrations experienced during road vs off-road cyclingrdquoInternational Journal of Sports Medicine 2015
[11] J Mester P Spitzenfeil J Schwarzer and F Seifriz ldquoBiologicalreaction to vibrationmdashimplications for sportrdquo Journal of Scienceand Medicine in Sport vol 2 no 3 pp 211ndash226 1999
[12] T Ishii Y Umerura and K Kitagawa ldquoInfluences of mountainbike suspension systems on energy supply and performancerdquoJapanese Journal of Biomechanics in Sports and Exercise vol 7pp 2ndash9 2003
[13] L M Sherwin P M O Owende C L Kanali J Lyons and SM Ward ldquoInfluence of tyre inflation pressure on whole-bodyvibrations transmitted to the operator in a cut-to-length timberharvesterrdquoApplied Ergonomics vol 35 no 3 pp 253ndash261 2004
[14] J Gordon J J Kauzlarich and J G Thacker ldquoTests of two newpolyurethane foam wheelchair tiresrdquo Journal of RehabilitationResearch and Development vol 26 no 1 pp 33ndash46 1989
[15] B J Sawatzky W O Kim and I Denison ldquoThe ergonomics ofdifferent tyres and tyre pressure during wheelchair propulsionrdquoErgonomics vol 47 no 14 pp 1475ndash1483 2004
[16] PWMacdermid PW Fink and S R Stannard ldquoThe influenceof tyre characteristics on measures of rolling performance dur-ing cross-country mountain bikingrdquo Journal of Sports Sciencesvol 33 no 3 pp 277ndash285 2015
[17] R Van der Plas Bicycle Technology Motorbooks International1991
[18] M Munera X Chiementin S Crequy and W Bertucci ldquoPhys-ical risk associated with vibration at cyclingrdquo Mechanics ampIndustry vol 15 no 6 pp 535ndash540 2014
[19] J Titlestad T Fairlie-Clarke A Whittaker M Davie I Wattand S Grant ldquoEffect of suspension systems on the physiologicaland psychological responses to sub-maximal biking on simu-lated smoothand bumpy tracksrdquo Journal of Sports Sciences vol24 no 2 pp 125ndash135 2006
[20] V B Issurin ldquoVibrations and their applications in sport areviewrdquo Journal of Sports Medicine and Physical Fitness vol 45no 3 pp 324ndash336 2005
[21] M Levy and G A Smith ldquoEffectiveness of vibration dampingwith bicycle suspension systemsrdquo Sports Engineering vol 8 no2 pp 99ndash106 2005
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Submit your manuscripts athttpwwwhindawicom
VLSI Design
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Shock and Vibration
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Civil EngineeringAdvances in
Acoustics and VibrationAdvances in
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Electrical and Computer Engineering
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International Journal of
2 Shock and Vibration
Table 1 Characteristics of the tyres used during the study
Tyre model Σ119879wt (g) ISOETRTO (mm) Est 119879vol (cm3) Manufacturer technology TPI Recommended tyre pressure (psi)
CycloXKing 760 35ndash622 1980 Performance 3180 56ndash85XKing 1380 55ndash622 5050 Performance 3180 50ndash65XKing 1470 60ndash622 6060 Performance 3180 50ndash65
an increase in the speed travelled per work done leadingto the positive outcome of improved performance over aXCO-MTB lap inclusive of additional rotational weight [9]Despite the fact that performance improved the increasedvibration exposure is still an issue with respect to potentialoveruse injuries and further performance enhancementSupplementary to the wheel size increase the tyre sizecombinedwith its inflated air pressure (psi) could assist recre-ational and competitive off-road cyclists to achieve a morecomfortable experience Work investigating related issuesin farm machinery operation have shown that increasingtyre inflation pressures were capable of considerable changes(up to 75) in estimated vibration exposure [13] This isfurther supported in wheelchair users [14] Yet paradoxicallyreduced tyre inflation pressures increased rolling resistanceby 35 amongst wheelchair users [14 15] Quantifying suchrelationships in terms of comfort and performance duringmountain biking is important to understand
The objective of this study was therefore to quantifythe influence of tyre size and inflation pressure on impactattenuation transmitted from surface terrain to bicycle andthe cyclist during the negotiation of a technical componentsimilar to that experienced during XCO-MTB racing It washypothesised that larger tyre sizes would lower the level ofimpact exposure experienced at the point of contact betweenbicycle and body while higher tyre inflation pressures withintyre sizes would increase the level of impact exposureAdditionally the benefit of tyre size could be negated throughhigh tyre pressures
2 Method
Twelve experienced mountain bikers (National (NZ) levelcross-country athletes) consented in accordance with theUniversity Human Ethics Committee to take part in thisstudy All participants used the same bicycle (GT Zaskar elite2910158401015840 Full Suspension Optimized Force Constructed CarbonUSA) adjusted to personal requirements prior to the trialand thus controlling posture The bicycle was fitted with afront (Rockshox Recon 100mm Solo Air USA) and rearsuspension (Fox Float CTD USA) system set as per themanufacturers recommendations for specific body weightsHowever both front suspension and rear suspension werethen switched to lock-outmode in order to allownomechani-cal damping as a result of suspensionTherefore any effect onacceleration measured would be as a result of the interven-tion(s)
21 Field Test Trial The experimental protocol involved thenegotiation of two flights of eight steps (dimension 26 times13 cm) equal throughout with the two flights separated by
A B
C
486m26 cm 26 cm
13 cm 13 cm
times8 times8
Figure 1 Pictorial representation of the experimental protocolwhere A signifies the start point with the front wheel B indicates thepoint at which timing commenced and C is where timing ceasedThe distance from A-B was dependent on the specific tyre rollout(see Table 1)
a distance of 486m (Figure 1) This obstacle was chosen inorder to simulate a moderatetypical technical downhill sec-tion on a cross country mountain bike course while beingable to control participant run up and the route taken It wasfelt that this aspect would be uncontrollable whilst riding across country mountain bike trail
Determination of the start position distance from the firststep was equal to wheel roll-out distance for specific tyre sizes(Table 1) This permitted participants one complete pedalstroke which started with the preferred lead foot at 45∘enabling them to hit point B (Figure 1) in the ready position(preferred foot and pedal at sim90∘ angle) just prior to negoti-ation of the steps The distance (A-B Figure 1) was equalledat the bottom of the second flight of stairs to mark the finish(C Figure 1) and allow the whole bicycle to have negotiatedthe second flight of steps Front chainring (36 tooth) and rearcassette cog (14 tooth) were standardised for all participantsthroughout the study
Participants completed six conditions including threedifferent tyres of the same tread pattern and constructionbut differing in size and weight (Table 1) For each tyre threetyre inflation pressures were selected based on the standard(22 Xking) XCO-MTB tyre and the typical inflation pressurevalues used by expert XCO-MTB cyclists and cited elsewhere[16]The standardised tyre inflation pressure value (tyre infla-tion pressure (moderate) for Xking 22) was 03 psi per totalweight (Bike + fully clothed and helmeted cyclist)
In order to calculate a proportional value for the otherconditions (nontypical XCO-MTB tyres including cycloXK-ing and Xking 24 Table 1) a ratio of estimated tyre volumebetween conditions was used This involved factorising thestandardised value for the 22 Xking tyre by 1629 and 0868
Shock and Vibration 3
(a)
(b)
Figure 2 Pictorial image of the two main tyres ((a) cyclocross and(b) mountain bike)
for the cycloXKing and Xking 24 tyres respectively Esti-mated tyre volume (Est119879vol) was based on ISOETRTOmea-surements [17] and Pappusrsquos centroid theorem for calculatingvolume of a torus (cm3) [16] From these values further fac-torising took place to establish a normalised and proportionallow (0666lowast) and high (1333lowast) tyre inflation pressure for alltyres Comparison of the three tyres and the inflation pres-sures can be seen in Figures 2 and 3
22 Outcome Measures Wireless triaxial accelerometersmagnetometers and gyroscopes with a reported accuracy00012msdots2 sdotradicHzminus1 (Emerald APDMORUSA)were used ina synchronised data-logging mode to measure accelerationsas previously reported during XCO-MTB [9]Through use ofa trigger to switch on the accelerometers performance time(s) was also recorded from point B-C Figure 1 The accelero-meters were placed on the lower left arm (frontal distal posi-tion) left lower leg (frontal distal position) seat post (within10 cm of the saddle-rider contact area) lumbar region of thelower back and medial forehead [9] All data was sampledat 128Hz logged to a standard personal computer convertedto a hierarchal data format file (h5) and processed usingMATLAB R2014a All data were analysed for total (119909- 119910-and 119911-axis) vertical (119911-axis) and horizontal (119909- and 119910-axis)accelerations Root mean squares (RMS) of the accelerationswere calculated to quantify overall effect of conditions whilespectral analysis was performed (Fast Fourier Transform)to determine maximum magnitude (m2sdotsminus4) maximum fre-quency (Hz) and quantification ofmovements as low (lt5Hz)and high (gt5Hz) power
23 Statistical Analyses Descriptive (mean plusmn SD) were cal-culated for all variables measured during each condition
Two-way repeated analysis of variance (ANOVA) withtwo within-subject variables (tyre size lowast tyre inflation pres-sure) was used to test differences in time to complete the pro-tocol with a Tukeyrsquos post hoc comparisonwithin tyre inflationpressure for each tyre
Low psi Moderate psi High psi0
10
20
30
CX22
Tyre pressure categorisation
24
Tyre
pre
ssur
e (ps
i)
Figure 3 Comparison of the three tyres and the respective inflationpressures used
Acceleration data comparisons were made via univariateanalysis of variance (three-way ANOVA) including within-subject variables tyre size tyre inflation pressure and accel-erometer location tested for main effects and interactions(tyre size lowast tyre inflation pressure lowast accelerometer locationtyre sizelowast tyre inflation pressure tyre sizelowast acceleration loca-tion and tyre inflation pressure lowast accelerometer location)Where significant difference was found the main effect wasanalysed using Bonferroni post hoc testing pairwise compar-ison
All statistical analyses were performed using IBM SPSSstatistics 20 significance set at 119875 lt 005
3 Results
31 Performance Analysis Participants completed a simu-lated technical component typical of the impacts associatedwith a XCO-MTB course [9]
Two-way ANOVA identified significant main effects fortyre size (119865
(233)= 4446 119875 lt 00001) but not tyre inflation
pressures within tyres (119865(233)= 1407 119875 = 02591) for time
to complete the trial (Figure 4) There was no interaction(119865(466)= 05676119875 = 06870) between tyre size and tyre infla-
tion pressure
32 Acceleration Data Analysis Three-way ANOVA of totalacceleration amplitude (RMS) showed that there was a signif-icant main effect for tyre size (119865
(233)= 72847 119875 lt 00001)
tyre inflation pressure (119865(233)= 38230 119875 lt 00001) and
accelerometer locations (119865(566)= 72847 119875 lt 00001) plus
an interaction (119865(9132)= 6114 119875 = 00001) between tyre size
and tyre inflation pressures (Figures 5(a)ndash5(c)) Key findingsfrom post hoc analysis showed differences for tyre size (119875 lt00001) between the cycloXKing (cx) and 22 XKing (95CI 0907ndash2102) cycloXKing and 24 XKing (95 CI 2406ndash3601) and 22 and 24 XKing (95 CI 0901ndash2096) tyre
4 Shock and Vibration
Low High0
1
2
3
4
5
ModerateNormalized tyre pressure
Tim
e (s)
CX (35mm)22 (55mm)24 (60mm)
lowastlowastlowastlowast
++++++++ ++++
+++++++ +++nabla
Figure 4 Mean plusmn SD for performance time (s) over the trialprotocol (Figure 1) lowastlowastlowastlowast(119875 lt 00001) main effect of tyre post hocdifferences when comparing tyres for within-tyre inflation pressureswhen compared to CX ++++(119875 lt 00001) +++(119875 lt 0001) and 22nabla(119875 lt 005)
inflation pressure (119875 lt 005) between pressure low andmoderate (95 CI minus1261ndashminus0066) low and high (95 CIminus2724ndashminus1529) and moderate and high (95 CI minus2060ndashminus0866) Multiple comparisons between the accelerometerlocations were significantly different (119875 lt 00001) except inthe case of the handlebar and seat post (119875 = 0824 95 CIminus0360ndash1714) and the lower back and forehead (119875 = 009295 CI minus0069ndash2005)
Significant main effects for vertical acceleration ampli-tude (RMS) for tyre size (119865
(233)= 16010 119875 lt 00001) tyre
inflation pressure (119865(233)= 17319 119875 lt 00001) and accel-
erometer location (119865(566)= 26543 119875 lt 00001) were found
(Figures 5(d)ndash5(f)) There were significant interactions bet-ween tyre size and accelerometer location (119865
(799)= 4657
119875 lt 00001) and tyre inflation pressure and accelerometerlocation (119865
(799)= 4253 119875 lt 00001) Post hoc analysis
showed significant differences (119875 lt 00001) for tyre sizebetween cycloXKing and 22 XKing (95 CI 0360ndash1163)and cycloXKing and 24 XKing (95 CI 0466ndash1270)normalised tyre inflation pressure between low and high(95 CI minus1347ndashminus05440) and moderate and high (95 CIminus01666ndash0637) Multiple comparisons between accelerome-ter locations were significantly different (119875 lt 001) except inthe case of the handlebar and wrist (119875 = 1000) and lowerback and forehead (119875 = 1000)
Horizontal accelerations (Figures 5(g)ndash5(i)) showedmaineffects for tyre size (119865
(233)= 35895 119875 lt 00001) tyre infla-
tion pressure (119865(233)= 10460 119875 lt 00001) and accelero-
meter location (119865(566)= 1548645 119875 lt 00001) with inter-
actions between tyre size lowast tyre inflation pressure (119865(466)=
3111 119875 = 00150) tyre size lowast accelerometer location(119865(799)= 10116 119875 lt 00001) and tyre inflation pressure lowast
accelerometer location (119865(799)= 1866 119875 = 00470) Post
hoc analysis identified differences between all tyre sizes (119875 lt001) between tyre inflation pressures low and high (119875 lt00001) and moderate and high (119875 = 00109) and betweenall accelerometer locations (119875 lt 005)
Three-way ANOVA of spectral analysis maximum fre-quency (Table 2) data provided a significant interactionbetween tyre size and accelerometer location (119865
(799)= 6700
119875 lt 00001) with a main effect of tyre size (119865(233)= 12553
119875 lt 00001) and accelerometer location (119865(566)= 51011 119875 lt
00001) Post hoc analysis identified differences between tyresizes cycloXKing and 22 XKing (95 CI minus02865ndashminus07662)and cycloXKing and 24 XKing (95 CI minus03017ndashminus00919)Data for maximummagnitude (Table 3) identified significantmain effects for tyre size (119865
(233)= 34420 119875 lt 00001)
tyre inflation pressure (119865(233)= 22864 119875 lt 00001) and
acceleration position (119865(566)= 3336605 119875 lt 00001) with
interactions between tyre size lowast accelerometer position(119865(799)= 10852 119875 lt 00001) and tyre inflation pressure lowast
accelerometer location (119865(799)= 4271 119875 lt 00001) Post hoc
analysis showed differences between tyre sizes occurred forcycloXKing and 2210158401015840 Xking (119875 = 00050) cycloXKing and2410158401015840 XKing (119875 lt 00001) and 2210158401015840 XKing and 2410158401015840 XKing(119875 lt 00001) tyre inflation pressure differences occurredbetween low and moderate (119875 = 0026) low and high(119875 lt 00001) and moderate and high (119875 = 00002) whiledifferences between all accelerometer positions (119875 lt 00500)except lower back and forehead (119875 gt 00500) occurred
Power data separated for low (lt5Hz) frequency (Table 4)identified significantmain effects for tyre size (119865
(233)= 5157
119875 = 00060) and accelerometer position (119865(566)= 1855902
119875 lt 00001) interactions between tyre size and accelerometerposition (119865
(799)= 1990 119875 = 00320) and tyre inflation pres-
sure and accelerometer position (119865(799)= 1998 119875 = 00310)
Post hoc differences for tyre size between cycloXKing and2210158401015840 XKing (95 CI minus04853ndashminus00693 119875 = 00040) werepresent and all accelerometer positions except the handlebarand seat post (119875 = 06330) High (gt5Hz) frequency (Table 4)showed significant main effects for tyre inflation pressure(119865(233)= 17516 119875 lt 00001) and accelerometer position
(119865(566)= 5190764 119875 lt 00001) with interactions for tyre
sizelowast tyre inflation pressure (119865(466)= 4210119875 = 00020) tyre
size lowast accelerometer position (119865(799)= 9575 119875 = 00070)
and tyre inflation pressure lowast accelerometer position (119865(799)=
2091 119875 = 00230) Post hoc analysis identified differenceswithin the tyre inflation factor between low andhigh pressure(95 CI minus15404ndashminus06302 119875 lt 00001) and moderate andhigh pressure (95 CI minus12441ndashminus03339 119875 lt 00001) Allaccelerometer positions were different (119875 lt 00001) exceptin the case of the handlebar and wrist (119875 = 07560) and thelower back and head (119875 = 10000)
4 Discussion
The aim of this study was to quantify the influence of tyresize and the normalised tyre inflation pressure on exposureto impacts and their interactions typical of that experiencedwhilst riding on a cross countrymountain bike trailThemainfindings were as follows (a) increases in tyre size led to
Shock and Vibration 5
Han
dleb
ar
Wris
t
Ank
le
Seat
pos
t
Lum
bar
Hea
d
Han
dleb
ar
Wris
t
Ank
le
Seat
pos
t
Lum
bar
Hea
d
Han
dleb
ar
Wris
t
Ank
le
Seat
pos
t
Lum
bar
Hea
d
Han
dleb
ar
Wris
t
Ank
le
Seat
pos
t
Lum
bar
Hea
d
Han
dleb
ar
Wris
t
Ank
le
Seat
pos
t
Lum
bar
Hea
d
Han
dleb
ar
Wris
t
Ank
le
Seat
pos
t
Lum
bar
Hea
d
Han
dleb
ar
Wris
t
Ank
le
Seat
pos
t
Lum
bar
Hea
d
Han
dleb
ar
Wris
t
Ank
le
Seat
pos
t
Lum
bar
Hea
d
Han
dleb
ar
Wris
t
Ank
le
Seat
pos
t
Lum
bar
Hea
d
(a) (b) (c)
(d) (e) (f)
(g) (h) (i)Normalised tyre inflation pressure Normalised tyre inflation pressure Normalised tyre inflation pressure
Low Moderate High
Acce
lera
tion
axis
Acce
lera
tion
axis
Acce
lera
tion
axis
Hor
izon
tal
Vert
ical
Tota
l
0102030405060
Acce
lera
tion
(mmiddotsminus
2)
0102030405060
Acce
lera
tion
(mmiddotsminus
2)
0102030405060
Acce
lera
tion
(mmiddotsminus
2)
0102030405060
Acce
lera
tion
(mmiddotsminus
2)
0102030405060
Acce
lera
tion
(mmiddotsminus
2)
0102030405060
Acce
lera
tion
(mmiddotsminus
2)
0102030405060
Acce
lera
tion
(mmiddotsminus
2)
0102030405060
Acce
lera
tion
(mmiddotsminus
2)
0102030405060
Acce
lera
tion
(mmiddotsminus
2)
Accelerometer position Accelerometer position Accelerometer position
poundpoundpoundpoundlowastlowast $$$$ otimesotimesotimesotimes nablanablanablanabla emptyemptyemptyempty
poundpoundpoundpound $$$$ otimesotimesotimesotimes nablanablanablanabla emptyemptyemptyempty
lowastlowastlowastlowast otimesotimesotimesotimes nablanablanablanabla emptyemptyemptyempty
Figure 5 Comparison between tyres (CycloXKing (black bar) 22 XKing (gray bar) and 24 XKing (white bar)) and three normalisedtyre inflation pressures characterised as low (1) normal (2) and high (3) for (a)ndash(c) Total accelerations (d)ndash(f) Vertical accelerations (g)ndash(i) Horizontal accelerations where lowast refers to the interaction for tyre size lowast tyre pressure (lowastlowastlowastlowast119875 lt 00001 lowastlowast119875 lt 001) $ refers to theinteraction for tyre sizelowast accelerometer location ($$$$119875 lt 00001) m refers to the interaction for tyre pressurelowast accelerometer location (mmmm119875 lt00001) otimesotimesotimesotimes(119875 lt 00001)main effect of tyre size OslashOslashOslashOslash(119875 lt 00001)main effect of tyre pressure nablanablanablanabla(119875 lt 00001)main effect of accelerometerlocation
positive effects on performance compared to tyre inflationpressure when riding down rough terrain (b) increases intyre size decrease the level of impact exposure experienced atpoint of contact(s) with the bicycle and thus reduce nonprop-ulsive work load (c) increased tyre inflation pressure intensi-fies exposure to acceleration exposure
Increased exposure to impacts and vibrations associatedwith forwards momentum of an off-road cyclist are linked toincreased nonpropulsive work [8] decreased efficiency [11]and performance [6 7] The reduction of this nonpropulsivework is thus potentially important with regard to competitiveperformance and theminimisation of overuse injury risk [18]
6 Shock and Vibration
Table2MeanplusmnSD
form
axim
umfre
quency
(Hz)of
acceleratio
nsdu
ringthetria
lseparatedfora
ccelerom
eter
locatio
ntyre
sizeandtyre
inflatio
npressure
Accelerometer
position
Cyclo
XKingtyreclubsclubsclubsclubs
2210158401015840XK
ingtyre
2410158401015840XK
ingtyre
3-way
ANOVA
LowPS
IMod
PSI
HighPS
ILo
wPS
IMod
PSI
HighPS
ILo
wPS
IMod
PSI
HighPS
IHandlebar
05284plusmn0049
05084plusmn004
605099plusmn006
005659plusmn0043
05632plusmn0036
05526plusmn0036
05781plusmn0029
060
03plusmn0055
05565plusmn0032
Tyrelowastlowastlowastlowast
PSIN
S
ALoclowastlowastlowastlowast
TyrelowastALoclowastlowastlowastlowast
Wris
t05284plusmn0049
05084plusmn004
605099plusmn006
005659plusmn0043
05632plusmn0037
05526plusmn0037
05781plusmn0029
060
03plusmn0055
05787plusmn0076
Ank
le05284plusmn0049
05084plusmn004
605099plusmn006
005659plusmn0043
05632plusmn0037
05526plusmn0036
05781plusmn0029
060
03plusmn0055
05787plusmn0032
Seatpo
st05284plusmn0049
05088plusmn0036
05099plusmn0036
05659plusmn0043
05654plusmn0036
05539plusmn0036
05781plusmn0029
060
03plusmn0055
05565plusmn0032
Lumbarotimesotimesotimesotimes
08372plusmn0760
08165plusmn0756
05345plusmn0123
13076plusmn1168
18315plusmn10
3416
682plusmn14
5320180plusmn14
2113
681plusmn
1034
14722plusmn1166
Forehead
05749plusmn0259
05088plusmn004
605099plusmn006
006518plusmn0284
05202plusmn0123
05098plusmn0121
05749plusmn0030
060
49plusmn0051
05117plusmn0117
Tyre(ty
resiz
e)PSI
(tyreinflatio
npressure)andALoc
(accelerom
eter
position)
refertothem
aineffectfor
maxim
umfre
quencyTyrelowast
ALoc
refersto
thetwo-way
interactionbetweentyresiz
eand
accelerometer
position
NSdeno
tesa
nonsignificanteffect(119875gt0005)lowastlowastlowastlowast(119875lt00001)clubsclubsclubsclubssig
nifiesa
postho
cdifference
(119875lt00001)for
tyre
sizew
hencomparin
gcyclo
XKingto
both
2210158401015840and2410158401015840XK
ingtyreotimesotimesotimesotimes
signifiesa
postho
cdifference
(119875lt00001)for
accelerometer
positionwhencomparedto
allother
accelerometer
positions
Shock and Vibration 7
Table3MeanplusmnSD
form
axim
ummagnitude
(g2 )of
acceleratio
nsdu
ringthetria
lseparatedfora
ccelerom
eter
locatio
ntyre
sizeandtyre
inflatio
npressure
Accelerometer
position
Cyclo
XKingtyre
2210158401015840XK
ingtyreclubsclubs
2410158401015840XK
ingtyreclubsclubsclubsclubs
3-way
ANOVA
LowPS
IMod
PSIoplus
HighPS
Ioplusoplus
LowPS
IMod
PSIoplus
HighPS
Ioplusoplus
LowPS
IMod
PSIoplus
HighPS
Ioplusoplus
Handlebar
96649plusmn0483
98169plusmn0837
99169plusmn0394
91121plusmn
0572
95915plusmn040
799
974plusmn0523
860
00plusmn076591403plusmn0489
96618plusmn0356
Tyrelowastlowastlowastlowast
PSIlowastlowastlowastlowast
ALoclowastlowastlowastlowast
TyrelowastALoclowastlowastlowastlowast
PSIlowast
ALoclowastlowastlowastlowast
Wris
t89805plusmn0969
92501plusmn
1016
93962plusmn0698
84191plusmn0744
86780plusmn0770
91158plusmn0944
80720plusmn0897
88992plusmn10
9285109plusmn0374
Ank
le104872plusmn0882106966plusmn12
44108250plusmn0903
90277plusmn13
9991
134plusmn0990
1015
14plusmn0970
86496plusmn14
3174
320plusmn0793
95862plusmn1127
Seatpo
st85581plusmn0596
88560plusmn10
0988657plusmn0831
85843plusmn10
9791
929plusmn0997
95898plusmn0936
81989plusmn14
0789681plusmn13
7592
576plusmn0977
Lumbar
09245plusmn0201
10165plusmn0315
09747plusmn0279
09550plusmn0198
09176plusmn0129
09810plusmn0169
08461plusmn0094
09134plusmn0124
09347plusmn0138
Forehead
12333plusmn0265
11829plusmn0106
12301plusmn
0220
10693plusmn
0184
11935plusmn0218
11763plusmn0147
11001plusmn
0150
10876plusmn0210
11283plusmn0244
Tyre(ty
resiz
e)PSI
(tyreinflatio
npressure)andALoc
(accelerom
eter
position)
refertothem
aineffectfor
maxim
umfre
quencyTyrelowast
ALoc
refersto
thetwo-way
interactionbetweentyresiz
eand
accelerometer
position
NSdeno
tesa
nonsignificanteffect(119875gt0005)lowastlowastlowastlowast(119875lt00001)clubsclubsclubsclubssig
nifiesa
postho
cdifference
(119875lt00001)a
ndclubsclubs(119875lt001)for
tyre
sizew
hencomparedto
cyclo
XKingtyreotimesotimesotimesotimessig
nifiesa
postho
cdifference
(119875lt00001)otimesandoplus(119875lt005)for
tyre
inflatio
npressure
whencomparedto
LowPS
Iandoplusoplus(119875lt0001)com
paredto
Mod
PSI
8 Shock and Vibration
Table4MeanplusmnSD
form
ovem
entsseparatedforlow
(lt5H
z)andhigh
(gt5H
z)po
wer
Accelerometer
position
Cyclo
Xkingtyre
2210158401015840XK
ingtyreclubsclubs
2410158401015840XK
ingtyre
3-way
ANOVA
LowPS
IMod
PSI
HighPS
ILo
wPS
IMod
PSIoplusoplusoplusoplus
HighPS
ILo
wPS
IMod
PSI
HighPS
Iotimesotimesotimesotimes
Lowpo
wer
hand
lebar
76020plusmn0372
73377plusmn0730
73461plusmn
0722
79999plusmn0706
80373plusmn0601
78545plusmn066
777
180plusmn0535
81915plusmn0921
73545plusmn0496
Tyrelowastlowastlowast
ALoclowastlowastlowastlowast
TyrelowastALoclowast
PSIlowast
ALoclowast
Wris
t1110
12plusmn14
331110
16plusmn0798
108242plusmn0665112274plusmn0783
113173plusmn0791
111153plusmn0940
107093plusmn0831
112719plusmn1111
1117
09plusmn14
81Ank
le88034plusmn12
8687661plusmn15
7491
143plusmn15
0485389plusmn15
5685304plusmn13
6793
778plusmn12
2886588plusmn18
5177
914plusmn0866
89735plusmn15
55Seatpo
st70
221plusmn
0892
69096plusmn1130
69559plusmn1100
77862plusmn0844
7740
8plusmn0802
76287plusmn0682
74695plusmn0979
81789plusmn15
9575
053plusmn0870
Lumbar
22323plusmn0428
22711plusmn0431
22088plusmn0555
23851plusmn0393
23896plusmn0385
24398plusmn0512
21917plusmn0240
21500plusmn0199
22178plusmn0242
Forehead
16805plusmn0125
15723plusmn0205
16235plusmn0241
17659plusmn0225
17505plusmn0263
15788plusmn0168
17763plusmn046
016
319plusmn0482
16620plusmn0461
Highpo
wer
hand
lebar
309527plusmn10
84316942plusmn2200
319095plusmn1144
313476plusmn16
95325003plusmn2085328681plusmn
1642
309170plusmn2816
325744plusmn2808338956plusmn2025PS
Ilowastlowastlowastlowast
ALoclowastlowastlowastlowast
TyrelowastPS
Ilowastlowast
TyrelowastALoclowastlowast
PSIlowast
ALoclowast
Wris
t310326plusmn17
613118
62plusmn19
44319101plusmn
1745
308851plusmn
1646
307399plusmn15
88324736plusmn18
583110
31plusmn16
343252
17plusmn2201
320763plusmn10
01Ank
le320164plusmn2753
307261plusmn
1813
308363plusmn19
35294291plusmn
1562
297999plusmn19
623119
27plusmn1746
299579plusmn4112
287204plusmn1748
3252
10plusmn2184
Seatpo
st343183plusmn2782
339910plusmn2618
3374
90plusmn19
463114
56plusmn2294324106plusmn204
8339546plusmn19
09306605plusmn4610324129plusmn356434364
6plusmn2565
Lumbar
540
80plusmn12
6055831plusmn0971
544
96plusmn1139
53255plusmn13
3454598plusmn12
1254818plusmn12
1248842plusmn0432
46912plusmn0481
53320plusmn0485
Forehead
55814plusmn13
9762502plusmn0620
58694plusmn0998
49398plusmn10
8350786plusmn14
2353796plusmn1525
57876plusmn1741
46845plusmn0808
59633plusmn15
70Where
tyre
(tyre
size)P
SI(ty
reinflatio
npressure)andALoc
(accele
rometer
locatio
n)refertothem
aineffectfor
power
band
Tyrelowast
ALoc
refersto
thetwo-way
interactionbetweentyre
sizea
ndaccelerometer
locatio
nlowastdeno
tessignificance
(119875lt005)lowastlowast(119875lt001)lowastlowastlowast(119875lt0001)lowastlowastlowastlowast(119875lt00001)clubsclubssig
nifiesa
postho
cdifference
(119875lt001)for
lowpo
wer
whencomparedto
cyclo
XKingtyre
sizeotimesotimesotimesotimessig
nifiesa
postho
cdifference
(119875lt00001)for
tyre
inflatio
npressure
whencomparedto
LowPS
Iandoplusoplusoplusoplus(119875lt00001)com
paredto
HighPS
I
Shock and Vibration 9
In the first instance Figure 4 identifies the highly signifi-cant (119875 lt 00001) effect of tyre size on performance timewithregard to normalised tyre inflation pressures This is furtherexacerbated considering the typical tyre inflation pressure(moderate Figure 3) used by competitive XCO-MTB athletes[16] At this pressure post hoc analysis identified differencesbetween 2210158401015840 and 2410158401015840 XKing tyres suggesting that tyre sizecould have considerable effect on performance
While difficult to glean conclusive data regarding overallXCO-MTB performance from such a small downhill com-ponent of performance as collected in this study it is worthnoting that previous research has linked decreased vibrationexposure to increased efficiency [10 11] As such the attenu-ation of accelerations experienced (Figure 5 and Tables 3 and4) at the point of contact between human and bicycle (han-dlebar and seat post) as a result of increased tyre size couldtheoretically be connected to overall performance duringcomplete race distance This obviously assumes that the dec-rease in nonpropulsive work would reduce muscular andcognitive fatigue and consequentially increase performanceHowever it is acknowledged that a complete XCO-MTB raceentails a variety of surfaces and terrains where themajority oftime is spent cycling uphill on smoother surfaces that mightactually suit a smaller higher pressure tyre As such futureresearch is needed to explore this aspect
On the other hand tyre inflation pressure does not seemto influence performance in this experiment (Figure 4) eventhough an increase in accelerations in all axes (Figure 5)related to an increase in magnitude (Table 3) rather than fre-quency (Table 2) was apparent While interesting the tran-sient nature of the protocol used cannot corroborate thelong term effects that racing for ge90mins with the observedincreases in magnitude would have on accumulated muscu-lar fatigue Based on previous laboratorywork [6 19] it is beli-eved that XCO-MTB performance would be compromisedover a complete race distance but requires confirmation
Similar to previous work on the transference of acceler-ations during XCO-MTB [9] the data presented here showsthat both the bicycle and the soft tissue are dissipating energy[20 21] from the interaction of bicycle with surface terrainimplying a reduced nonpropulsive work component of XCO-MTB as a result of increased tyre size This is supportedthrough two-way interactions between both tyre size lowast accel-erometer position and tyre inflation pressure lowast accelero-meter location for total vertical and horizontal accelera-tions (Figure 5) magnitude (Table 3) and low-high powerdistribution (Table 4) As such the reduction in measuresassociated with acceleration exposure reported previouslydecreased at the point of interaction with the bicycle withan increase in tyre size Importantly this was accompaniedby reductions at the soft tissue sites implying a reduced non-propulsive work component of XCO-MTB as a result ofincreased tyre size Alternatively increases in tyre inflationpressure have the opposite and negative effect by increasingrider exposure to accelerations at the point of interface withbicycle and thus increase the non-propulsive componentAdditionally the controlled nature of this protocol mayenable participants to alter body position or riding style
dependent on tyre chracteristics not afforded during a racingsituation
5 Conclusion
This study set out to quantify the influence of tyre size andnormalised tyre inflation pressure on exposure to impactstypical to cross country mountain bike riding It was foundthat the larger the tyre size within the range tested thelower the level of impact exposure experienced at the pointof contact between bicycle and body This reduction meantparticipants performed less non-propulsive muscular workand performed better when compared to a smaller tyre of thesame construction and tread pattern Contrariwise highertyre inflation pressures were associated with an increase inthe level of impact exposure and thus greater soft tissue workin order to attenuate the larger impacts In addition it wasshown that increased tyre inflation pressure could interactnegatively with tyre size while increased tyre size couldinteract positively with tyre inflation pressure As such theeffects of reduced exposure need to be assessed with regardsto longer periods of time such as experienced in a mountainbike race or recreational ride
6 Practical Application
It is recommended that participants (recreational and com-petitive) use a higher volume tyre over any smaller alternativewithin the range tested here In doing so it is suggested thatparticipants could improve performance and likely reducethe risk of overuse injuries or increase the time spent ridingfor the same risk(s)
It is important to note that two-way interactions betweentyre size and tyre inflation pressures suggest that the benefitsof riding with a bigger tyre could be negated through the useof high tyre inflation pressure Conversely the use of lowertyre inflation pressures in smaller tyres could reduce exposurebut must come with a warning of increased unreliability interms of punctures and de-beading from the wheel rim
7 Future Research
The findings of this study must now be verified over a com-plete XCO-MTB race lap consisting of a variety of terrainsto enable whole performance analysis and terrain specificsection performance analysis
Conflict of Interests
The authors declare that there is no conflict of interestsregarding the publication of this paper
References
[1] H THurst and S Atkins ldquoPower output of field-based downhillmountain bikingrdquo Journal of Sports Sciences vol 24 no 10 pp1047ndash1053 2006
[2] F M Impellizzeri and S M Marcora ldquoThe physiology ofmountain bikingrdquo SportsMedicine vol 37 no 1 pp 59ndash71 2007
10 Shock and Vibration
[3] P W Macdermid and S Stannard ldquoMechanical work andphysiological responses to simulated cross country mountainbike racingrdquo Journal of Sports Sciences vol 30 no 14 pp 1491ndash1501 2012
[4] B Stapelfeldt A Schwirtz Y O Schumacher and M Hille-brecht ldquoWorkload demands in mountain bike racingrdquo Interna-tional Journal of Sports Medicine vol 25 no 4 pp 294ndash3002004
[5] P Macdermid P Fink and S Stannard ldquoThe effects of vibra-tions experienced during road vs off-road cyclingrdquo Interna-tional Journal of Sports Medicine 2015
[6] B Samuelson L Jorfeldt and B Ahlborg ldquoInfluence of vibra-tion on endurance of maximal isometric contractionrdquo ClinicalPhysiology vol 9 no 1 pp 21ndash25 1989
[7] J Titlestad A Fairlie-Clarke M Davie A Whittaker and SGrant ldquoExperimental evaluation of mountain bike suspensionsystemsrdquo Acta Polytechnica vol 43 no 5 2003
[8] H T Hurst M Swaren K Hebert-Losier et al ldquoInfluenceof course type on upper body muscle activity in elite Cross-Country andDownhillmountain bikers during offRoadDown-hill Cyclingrdquo Journal of Science and Cycling vol 1 no 2 pp 2ndash92012
[9] P W Macdermid P W Fink and S R Stannard ldquoTransferenceof 3D accelerations during cross country mountain bikingrdquoJournal of Biomechanics vol 47 no 8 pp 1829ndash1837 2014
[10] P W Macdermid P W Fink and S R Stannard ldquoThe effectsof vibrations experienced during road vs off-road cyclingrdquoInternational Journal of Sports Medicine 2015
[11] J Mester P Spitzenfeil J Schwarzer and F Seifriz ldquoBiologicalreaction to vibrationmdashimplications for sportrdquo Journal of Scienceand Medicine in Sport vol 2 no 3 pp 211ndash226 1999
[12] T Ishii Y Umerura and K Kitagawa ldquoInfluences of mountainbike suspension systems on energy supply and performancerdquoJapanese Journal of Biomechanics in Sports and Exercise vol 7pp 2ndash9 2003
[13] L M Sherwin P M O Owende C L Kanali J Lyons and SM Ward ldquoInfluence of tyre inflation pressure on whole-bodyvibrations transmitted to the operator in a cut-to-length timberharvesterrdquoApplied Ergonomics vol 35 no 3 pp 253ndash261 2004
[14] J Gordon J J Kauzlarich and J G Thacker ldquoTests of two newpolyurethane foam wheelchair tiresrdquo Journal of RehabilitationResearch and Development vol 26 no 1 pp 33ndash46 1989
[15] B J Sawatzky W O Kim and I Denison ldquoThe ergonomics ofdifferent tyres and tyre pressure during wheelchair propulsionrdquoErgonomics vol 47 no 14 pp 1475ndash1483 2004
[16] PWMacdermid PW Fink and S R Stannard ldquoThe influenceof tyre characteristics on measures of rolling performance dur-ing cross-country mountain bikingrdquo Journal of Sports Sciencesvol 33 no 3 pp 277ndash285 2015
[17] R Van der Plas Bicycle Technology Motorbooks International1991
[18] M Munera X Chiementin S Crequy and W Bertucci ldquoPhys-ical risk associated with vibration at cyclingrdquo Mechanics ampIndustry vol 15 no 6 pp 535ndash540 2014
[19] J Titlestad T Fairlie-Clarke A Whittaker M Davie I Wattand S Grant ldquoEffect of suspension systems on the physiologicaland psychological responses to sub-maximal biking on simu-lated smoothand bumpy tracksrdquo Journal of Sports Sciences vol24 no 2 pp 125ndash135 2006
[20] V B Issurin ldquoVibrations and their applications in sport areviewrdquo Journal of Sports Medicine and Physical Fitness vol 45no 3 pp 324ndash336 2005
[21] M Levy and G A Smith ldquoEffectiveness of vibration dampingwith bicycle suspension systemsrdquo Sports Engineering vol 8 no2 pp 99ndash106 2005
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Shock and Vibration
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Shock and Vibration 3
(a)
(b)
Figure 2 Pictorial image of the two main tyres ((a) cyclocross and(b) mountain bike)
for the cycloXKing and Xking 24 tyres respectively Esti-mated tyre volume (Est119879vol) was based on ISOETRTOmea-surements [17] and Pappusrsquos centroid theorem for calculatingvolume of a torus (cm3) [16] From these values further fac-torising took place to establish a normalised and proportionallow (0666lowast) and high (1333lowast) tyre inflation pressure for alltyres Comparison of the three tyres and the inflation pres-sures can be seen in Figures 2 and 3
22 Outcome Measures Wireless triaxial accelerometersmagnetometers and gyroscopes with a reported accuracy00012msdots2 sdotradicHzminus1 (Emerald APDMORUSA)were used ina synchronised data-logging mode to measure accelerationsas previously reported during XCO-MTB [9]Through use ofa trigger to switch on the accelerometers performance time(s) was also recorded from point B-C Figure 1 The accelero-meters were placed on the lower left arm (frontal distal posi-tion) left lower leg (frontal distal position) seat post (within10 cm of the saddle-rider contact area) lumbar region of thelower back and medial forehead [9] All data was sampledat 128Hz logged to a standard personal computer convertedto a hierarchal data format file (h5) and processed usingMATLAB R2014a All data were analysed for total (119909- 119910-and 119911-axis) vertical (119911-axis) and horizontal (119909- and 119910-axis)accelerations Root mean squares (RMS) of the accelerationswere calculated to quantify overall effect of conditions whilespectral analysis was performed (Fast Fourier Transform)to determine maximum magnitude (m2sdotsminus4) maximum fre-quency (Hz) and quantification ofmovements as low (lt5Hz)and high (gt5Hz) power
23 Statistical Analyses Descriptive (mean plusmn SD) were cal-culated for all variables measured during each condition
Two-way repeated analysis of variance (ANOVA) withtwo within-subject variables (tyre size lowast tyre inflation pres-sure) was used to test differences in time to complete the pro-tocol with a Tukeyrsquos post hoc comparisonwithin tyre inflationpressure for each tyre
Low psi Moderate psi High psi0
10
20
30
CX22
Tyre pressure categorisation
24
Tyre
pre
ssur
e (ps
i)
Figure 3 Comparison of the three tyres and the respective inflationpressures used
Acceleration data comparisons were made via univariateanalysis of variance (three-way ANOVA) including within-subject variables tyre size tyre inflation pressure and accel-erometer location tested for main effects and interactions(tyre size lowast tyre inflation pressure lowast accelerometer locationtyre sizelowast tyre inflation pressure tyre sizelowast acceleration loca-tion and tyre inflation pressure lowast accelerometer location)Where significant difference was found the main effect wasanalysed using Bonferroni post hoc testing pairwise compar-ison
All statistical analyses were performed using IBM SPSSstatistics 20 significance set at 119875 lt 005
3 Results
31 Performance Analysis Participants completed a simu-lated technical component typical of the impacts associatedwith a XCO-MTB course [9]
Two-way ANOVA identified significant main effects fortyre size (119865
(233)= 4446 119875 lt 00001) but not tyre inflation
pressures within tyres (119865(233)= 1407 119875 = 02591) for time
to complete the trial (Figure 4) There was no interaction(119865(466)= 05676119875 = 06870) between tyre size and tyre infla-
tion pressure
32 Acceleration Data Analysis Three-way ANOVA of totalacceleration amplitude (RMS) showed that there was a signif-icant main effect for tyre size (119865
(233)= 72847 119875 lt 00001)
tyre inflation pressure (119865(233)= 38230 119875 lt 00001) and
accelerometer locations (119865(566)= 72847 119875 lt 00001) plus
an interaction (119865(9132)= 6114 119875 = 00001) between tyre size
and tyre inflation pressures (Figures 5(a)ndash5(c)) Key findingsfrom post hoc analysis showed differences for tyre size (119875 lt00001) between the cycloXKing (cx) and 22 XKing (95CI 0907ndash2102) cycloXKing and 24 XKing (95 CI 2406ndash3601) and 22 and 24 XKing (95 CI 0901ndash2096) tyre
4 Shock and Vibration
Low High0
1
2
3
4
5
ModerateNormalized tyre pressure
Tim
e (s)
CX (35mm)22 (55mm)24 (60mm)
lowastlowastlowastlowast
++++++++ ++++
+++++++ +++nabla
Figure 4 Mean plusmn SD for performance time (s) over the trialprotocol (Figure 1) lowastlowastlowastlowast(119875 lt 00001) main effect of tyre post hocdifferences when comparing tyres for within-tyre inflation pressureswhen compared to CX ++++(119875 lt 00001) +++(119875 lt 0001) and 22nabla(119875 lt 005)
inflation pressure (119875 lt 005) between pressure low andmoderate (95 CI minus1261ndashminus0066) low and high (95 CIminus2724ndashminus1529) and moderate and high (95 CI minus2060ndashminus0866) Multiple comparisons between the accelerometerlocations were significantly different (119875 lt 00001) except inthe case of the handlebar and seat post (119875 = 0824 95 CIminus0360ndash1714) and the lower back and forehead (119875 = 009295 CI minus0069ndash2005)
Significant main effects for vertical acceleration ampli-tude (RMS) for tyre size (119865
(233)= 16010 119875 lt 00001) tyre
inflation pressure (119865(233)= 17319 119875 lt 00001) and accel-
erometer location (119865(566)= 26543 119875 lt 00001) were found
(Figures 5(d)ndash5(f)) There were significant interactions bet-ween tyre size and accelerometer location (119865
(799)= 4657
119875 lt 00001) and tyre inflation pressure and accelerometerlocation (119865
(799)= 4253 119875 lt 00001) Post hoc analysis
showed significant differences (119875 lt 00001) for tyre sizebetween cycloXKing and 22 XKing (95 CI 0360ndash1163)and cycloXKing and 24 XKing (95 CI 0466ndash1270)normalised tyre inflation pressure between low and high(95 CI minus1347ndashminus05440) and moderate and high (95 CIminus01666ndash0637) Multiple comparisons between accelerome-ter locations were significantly different (119875 lt 001) except inthe case of the handlebar and wrist (119875 = 1000) and lowerback and forehead (119875 = 1000)
Horizontal accelerations (Figures 5(g)ndash5(i)) showedmaineffects for tyre size (119865
(233)= 35895 119875 lt 00001) tyre infla-
tion pressure (119865(233)= 10460 119875 lt 00001) and accelero-
meter location (119865(566)= 1548645 119875 lt 00001) with inter-
actions between tyre size lowast tyre inflation pressure (119865(466)=
3111 119875 = 00150) tyre size lowast accelerometer location(119865(799)= 10116 119875 lt 00001) and tyre inflation pressure lowast
accelerometer location (119865(799)= 1866 119875 = 00470) Post
hoc analysis identified differences between all tyre sizes (119875 lt001) between tyre inflation pressures low and high (119875 lt00001) and moderate and high (119875 = 00109) and betweenall accelerometer locations (119875 lt 005)
Three-way ANOVA of spectral analysis maximum fre-quency (Table 2) data provided a significant interactionbetween tyre size and accelerometer location (119865
(799)= 6700
119875 lt 00001) with a main effect of tyre size (119865(233)= 12553
119875 lt 00001) and accelerometer location (119865(566)= 51011 119875 lt
00001) Post hoc analysis identified differences between tyresizes cycloXKing and 22 XKing (95 CI minus02865ndashminus07662)and cycloXKing and 24 XKing (95 CI minus03017ndashminus00919)Data for maximummagnitude (Table 3) identified significantmain effects for tyre size (119865
(233)= 34420 119875 lt 00001)
tyre inflation pressure (119865(233)= 22864 119875 lt 00001) and
acceleration position (119865(566)= 3336605 119875 lt 00001) with
interactions between tyre size lowast accelerometer position(119865(799)= 10852 119875 lt 00001) and tyre inflation pressure lowast
accelerometer location (119865(799)= 4271 119875 lt 00001) Post hoc
analysis showed differences between tyre sizes occurred forcycloXKing and 2210158401015840 Xking (119875 = 00050) cycloXKing and2410158401015840 XKing (119875 lt 00001) and 2210158401015840 XKing and 2410158401015840 XKing(119875 lt 00001) tyre inflation pressure differences occurredbetween low and moderate (119875 = 0026) low and high(119875 lt 00001) and moderate and high (119875 = 00002) whiledifferences between all accelerometer positions (119875 lt 00500)except lower back and forehead (119875 gt 00500) occurred
Power data separated for low (lt5Hz) frequency (Table 4)identified significantmain effects for tyre size (119865
(233)= 5157
119875 = 00060) and accelerometer position (119865(566)= 1855902
119875 lt 00001) interactions between tyre size and accelerometerposition (119865
(799)= 1990 119875 = 00320) and tyre inflation pres-
sure and accelerometer position (119865(799)= 1998 119875 = 00310)
Post hoc differences for tyre size between cycloXKing and2210158401015840 XKing (95 CI minus04853ndashminus00693 119875 = 00040) werepresent and all accelerometer positions except the handlebarand seat post (119875 = 06330) High (gt5Hz) frequency (Table 4)showed significant main effects for tyre inflation pressure(119865(233)= 17516 119875 lt 00001) and accelerometer position
(119865(566)= 5190764 119875 lt 00001) with interactions for tyre
sizelowast tyre inflation pressure (119865(466)= 4210119875 = 00020) tyre
size lowast accelerometer position (119865(799)= 9575 119875 = 00070)
and tyre inflation pressure lowast accelerometer position (119865(799)=
2091 119875 = 00230) Post hoc analysis identified differenceswithin the tyre inflation factor between low andhigh pressure(95 CI minus15404ndashminus06302 119875 lt 00001) and moderate andhigh pressure (95 CI minus12441ndashminus03339 119875 lt 00001) Allaccelerometer positions were different (119875 lt 00001) exceptin the case of the handlebar and wrist (119875 = 07560) and thelower back and head (119875 = 10000)
4 Discussion
The aim of this study was to quantify the influence of tyresize and the normalised tyre inflation pressure on exposureto impacts and their interactions typical of that experiencedwhilst riding on a cross countrymountain bike trailThemainfindings were as follows (a) increases in tyre size led to
Shock and Vibration 5
Han
dleb
ar
Wris
t
Ank
le
Seat
pos
t
Lum
bar
Hea
d
Han
dleb
ar
Wris
t
Ank
le
Seat
pos
t
Lum
bar
Hea
d
Han
dleb
ar
Wris
t
Ank
le
Seat
pos
t
Lum
bar
Hea
d
Han
dleb
ar
Wris
t
Ank
le
Seat
pos
t
Lum
bar
Hea
d
Han
dleb
ar
Wris
t
Ank
le
Seat
pos
t
Lum
bar
Hea
d
Han
dleb
ar
Wris
t
Ank
le
Seat
pos
t
Lum
bar
Hea
d
Han
dleb
ar
Wris
t
Ank
le
Seat
pos
t
Lum
bar
Hea
d
Han
dleb
ar
Wris
t
Ank
le
Seat
pos
t
Lum
bar
Hea
d
Han
dleb
ar
Wris
t
Ank
le
Seat
pos
t
Lum
bar
Hea
d
(a) (b) (c)
(d) (e) (f)
(g) (h) (i)Normalised tyre inflation pressure Normalised tyre inflation pressure Normalised tyre inflation pressure
Low Moderate High
Acce
lera
tion
axis
Acce
lera
tion
axis
Acce
lera
tion
axis
Hor
izon
tal
Vert
ical
Tota
l
0102030405060
Acce
lera
tion
(mmiddotsminus
2)
0102030405060
Acce
lera
tion
(mmiddotsminus
2)
0102030405060
Acce
lera
tion
(mmiddotsminus
2)
0102030405060
Acce
lera
tion
(mmiddotsminus
2)
0102030405060
Acce
lera
tion
(mmiddotsminus
2)
0102030405060
Acce
lera
tion
(mmiddotsminus
2)
0102030405060
Acce
lera
tion
(mmiddotsminus
2)
0102030405060
Acce
lera
tion
(mmiddotsminus
2)
0102030405060
Acce
lera
tion
(mmiddotsminus
2)
Accelerometer position Accelerometer position Accelerometer position
poundpoundpoundpoundlowastlowast $$$$ otimesotimesotimesotimes nablanablanablanabla emptyemptyemptyempty
poundpoundpoundpound $$$$ otimesotimesotimesotimes nablanablanablanabla emptyemptyemptyempty
lowastlowastlowastlowast otimesotimesotimesotimes nablanablanablanabla emptyemptyemptyempty
Figure 5 Comparison between tyres (CycloXKing (black bar) 22 XKing (gray bar) and 24 XKing (white bar)) and three normalisedtyre inflation pressures characterised as low (1) normal (2) and high (3) for (a)ndash(c) Total accelerations (d)ndash(f) Vertical accelerations (g)ndash(i) Horizontal accelerations where lowast refers to the interaction for tyre size lowast tyre pressure (lowastlowastlowastlowast119875 lt 00001 lowastlowast119875 lt 001) $ refers to theinteraction for tyre sizelowast accelerometer location ($$$$119875 lt 00001) m refers to the interaction for tyre pressurelowast accelerometer location (mmmm119875 lt00001) otimesotimesotimesotimes(119875 lt 00001)main effect of tyre size OslashOslashOslashOslash(119875 lt 00001)main effect of tyre pressure nablanablanablanabla(119875 lt 00001)main effect of accelerometerlocation
positive effects on performance compared to tyre inflationpressure when riding down rough terrain (b) increases intyre size decrease the level of impact exposure experienced atpoint of contact(s) with the bicycle and thus reduce nonprop-ulsive work load (c) increased tyre inflation pressure intensi-fies exposure to acceleration exposure
Increased exposure to impacts and vibrations associatedwith forwards momentum of an off-road cyclist are linked toincreased nonpropulsive work [8] decreased efficiency [11]and performance [6 7] The reduction of this nonpropulsivework is thus potentially important with regard to competitiveperformance and theminimisation of overuse injury risk [18]
6 Shock and Vibration
Table2MeanplusmnSD
form
axim
umfre
quency
(Hz)of
acceleratio
nsdu
ringthetria
lseparatedfora
ccelerom
eter
locatio
ntyre
sizeandtyre
inflatio
npressure
Accelerometer
position
Cyclo
XKingtyreclubsclubsclubsclubs
2210158401015840XK
ingtyre
2410158401015840XK
ingtyre
3-way
ANOVA
LowPS
IMod
PSI
HighPS
ILo
wPS
IMod
PSI
HighPS
ILo
wPS
IMod
PSI
HighPS
IHandlebar
05284plusmn0049
05084plusmn004
605099plusmn006
005659plusmn0043
05632plusmn0036
05526plusmn0036
05781plusmn0029
060
03plusmn0055
05565plusmn0032
Tyrelowastlowastlowastlowast
PSIN
S
ALoclowastlowastlowastlowast
TyrelowastALoclowastlowastlowastlowast
Wris
t05284plusmn0049
05084plusmn004
605099plusmn006
005659plusmn0043
05632plusmn0037
05526plusmn0037
05781plusmn0029
060
03plusmn0055
05787plusmn0076
Ank
le05284plusmn0049
05084plusmn004
605099plusmn006
005659plusmn0043
05632plusmn0037
05526plusmn0036
05781plusmn0029
060
03plusmn0055
05787plusmn0032
Seatpo
st05284plusmn0049
05088plusmn0036
05099plusmn0036
05659plusmn0043
05654plusmn0036
05539plusmn0036
05781plusmn0029
060
03plusmn0055
05565plusmn0032
Lumbarotimesotimesotimesotimes
08372plusmn0760
08165plusmn0756
05345plusmn0123
13076plusmn1168
18315plusmn10
3416
682plusmn14
5320180plusmn14
2113
681plusmn
1034
14722plusmn1166
Forehead
05749plusmn0259
05088plusmn004
605099plusmn006
006518plusmn0284
05202plusmn0123
05098plusmn0121
05749plusmn0030
060
49plusmn0051
05117plusmn0117
Tyre(ty
resiz
e)PSI
(tyreinflatio
npressure)andALoc
(accelerom
eter
position)
refertothem
aineffectfor
maxim
umfre
quencyTyrelowast
ALoc
refersto
thetwo-way
interactionbetweentyresiz
eand
accelerometer
position
NSdeno
tesa
nonsignificanteffect(119875gt0005)lowastlowastlowastlowast(119875lt00001)clubsclubsclubsclubssig
nifiesa
postho
cdifference
(119875lt00001)for
tyre
sizew
hencomparin
gcyclo
XKingto
both
2210158401015840and2410158401015840XK
ingtyreotimesotimesotimesotimes
signifiesa
postho
cdifference
(119875lt00001)for
accelerometer
positionwhencomparedto
allother
accelerometer
positions
Shock and Vibration 7
Table3MeanplusmnSD
form
axim
ummagnitude
(g2 )of
acceleratio
nsdu
ringthetria
lseparatedfora
ccelerom
eter
locatio
ntyre
sizeandtyre
inflatio
npressure
Accelerometer
position
Cyclo
XKingtyre
2210158401015840XK
ingtyreclubsclubs
2410158401015840XK
ingtyreclubsclubsclubsclubs
3-way
ANOVA
LowPS
IMod
PSIoplus
HighPS
Ioplusoplus
LowPS
IMod
PSIoplus
HighPS
Ioplusoplus
LowPS
IMod
PSIoplus
HighPS
Ioplusoplus
Handlebar
96649plusmn0483
98169plusmn0837
99169plusmn0394
91121plusmn
0572
95915plusmn040
799
974plusmn0523
860
00plusmn076591403plusmn0489
96618plusmn0356
Tyrelowastlowastlowastlowast
PSIlowastlowastlowastlowast
ALoclowastlowastlowastlowast
TyrelowastALoclowastlowastlowastlowast
PSIlowast
ALoclowastlowastlowastlowast
Wris
t89805plusmn0969
92501plusmn
1016
93962plusmn0698
84191plusmn0744
86780plusmn0770
91158plusmn0944
80720plusmn0897
88992plusmn10
9285109plusmn0374
Ank
le104872plusmn0882106966plusmn12
44108250plusmn0903
90277plusmn13
9991
134plusmn0990
1015
14plusmn0970
86496plusmn14
3174
320plusmn0793
95862plusmn1127
Seatpo
st85581plusmn0596
88560plusmn10
0988657plusmn0831
85843plusmn10
9791
929plusmn0997
95898plusmn0936
81989plusmn14
0789681plusmn13
7592
576plusmn0977
Lumbar
09245plusmn0201
10165plusmn0315
09747plusmn0279
09550plusmn0198
09176plusmn0129
09810plusmn0169
08461plusmn0094
09134plusmn0124
09347plusmn0138
Forehead
12333plusmn0265
11829plusmn0106
12301plusmn
0220
10693plusmn
0184
11935plusmn0218
11763plusmn0147
11001plusmn
0150
10876plusmn0210
11283plusmn0244
Tyre(ty
resiz
e)PSI
(tyreinflatio
npressure)andALoc
(accelerom
eter
position)
refertothem
aineffectfor
maxim
umfre
quencyTyrelowast
ALoc
refersto
thetwo-way
interactionbetweentyresiz
eand
accelerometer
position
NSdeno
tesa
nonsignificanteffect(119875gt0005)lowastlowastlowastlowast(119875lt00001)clubsclubsclubsclubssig
nifiesa
postho
cdifference
(119875lt00001)a
ndclubsclubs(119875lt001)for
tyre
sizew
hencomparedto
cyclo
XKingtyreotimesotimesotimesotimessig
nifiesa
postho
cdifference
(119875lt00001)otimesandoplus(119875lt005)for
tyre
inflatio
npressure
whencomparedto
LowPS
Iandoplusoplus(119875lt0001)com
paredto
Mod
PSI
8 Shock and Vibration
Table4MeanplusmnSD
form
ovem
entsseparatedforlow
(lt5H
z)andhigh
(gt5H
z)po
wer
Accelerometer
position
Cyclo
Xkingtyre
2210158401015840XK
ingtyreclubsclubs
2410158401015840XK
ingtyre
3-way
ANOVA
LowPS
IMod
PSI
HighPS
ILo
wPS
IMod
PSIoplusoplusoplusoplus
HighPS
ILo
wPS
IMod
PSI
HighPS
Iotimesotimesotimesotimes
Lowpo
wer
hand
lebar
76020plusmn0372
73377plusmn0730
73461plusmn
0722
79999plusmn0706
80373plusmn0601
78545plusmn066
777
180plusmn0535
81915plusmn0921
73545plusmn0496
Tyrelowastlowastlowast
ALoclowastlowastlowastlowast
TyrelowastALoclowast
PSIlowast
ALoclowast
Wris
t1110
12plusmn14
331110
16plusmn0798
108242plusmn0665112274plusmn0783
113173plusmn0791
111153plusmn0940
107093plusmn0831
112719plusmn1111
1117
09plusmn14
81Ank
le88034plusmn12
8687661plusmn15
7491
143plusmn15
0485389plusmn15
5685304plusmn13
6793
778plusmn12
2886588plusmn18
5177
914plusmn0866
89735plusmn15
55Seatpo
st70
221plusmn
0892
69096plusmn1130
69559plusmn1100
77862plusmn0844
7740
8plusmn0802
76287plusmn0682
74695plusmn0979
81789plusmn15
9575
053plusmn0870
Lumbar
22323plusmn0428
22711plusmn0431
22088plusmn0555
23851plusmn0393
23896plusmn0385
24398plusmn0512
21917plusmn0240
21500plusmn0199
22178plusmn0242
Forehead
16805plusmn0125
15723plusmn0205
16235plusmn0241
17659plusmn0225
17505plusmn0263
15788plusmn0168
17763plusmn046
016
319plusmn0482
16620plusmn0461
Highpo
wer
hand
lebar
309527plusmn10
84316942plusmn2200
319095plusmn1144
313476plusmn16
95325003plusmn2085328681plusmn
1642
309170plusmn2816
325744plusmn2808338956plusmn2025PS
Ilowastlowastlowastlowast
ALoclowastlowastlowastlowast
TyrelowastPS
Ilowastlowast
TyrelowastALoclowastlowast
PSIlowast
ALoclowast
Wris
t310326plusmn17
613118
62plusmn19
44319101plusmn
1745
308851plusmn
1646
307399plusmn15
88324736plusmn18
583110
31plusmn16
343252
17plusmn2201
320763plusmn10
01Ank
le320164plusmn2753
307261plusmn
1813
308363plusmn19
35294291plusmn
1562
297999plusmn19
623119
27plusmn1746
299579plusmn4112
287204plusmn1748
3252
10plusmn2184
Seatpo
st343183plusmn2782
339910plusmn2618
3374
90plusmn19
463114
56plusmn2294324106plusmn204
8339546plusmn19
09306605plusmn4610324129plusmn356434364
6plusmn2565
Lumbar
540
80plusmn12
6055831plusmn0971
544
96plusmn1139
53255plusmn13
3454598plusmn12
1254818plusmn12
1248842plusmn0432
46912plusmn0481
53320plusmn0485
Forehead
55814plusmn13
9762502plusmn0620
58694plusmn0998
49398plusmn10
8350786plusmn14
2353796plusmn1525
57876plusmn1741
46845plusmn0808
59633plusmn15
70Where
tyre
(tyre
size)P
SI(ty
reinflatio
npressure)andALoc
(accele
rometer
locatio
n)refertothem
aineffectfor
power
band
Tyrelowast
ALoc
refersto
thetwo-way
interactionbetweentyre
sizea
ndaccelerometer
locatio
nlowastdeno
tessignificance
(119875lt005)lowastlowast(119875lt001)lowastlowastlowast(119875lt0001)lowastlowastlowastlowast(119875lt00001)clubsclubssig
nifiesa
postho
cdifference
(119875lt001)for
lowpo
wer
whencomparedto
cyclo
XKingtyre
sizeotimesotimesotimesotimessig
nifiesa
postho
cdifference
(119875lt00001)for
tyre
inflatio
npressure
whencomparedto
LowPS
Iandoplusoplusoplusoplus(119875lt00001)com
paredto
HighPS
I
Shock and Vibration 9
In the first instance Figure 4 identifies the highly signifi-cant (119875 lt 00001) effect of tyre size on performance timewithregard to normalised tyre inflation pressures This is furtherexacerbated considering the typical tyre inflation pressure(moderate Figure 3) used by competitive XCO-MTB athletes[16] At this pressure post hoc analysis identified differencesbetween 2210158401015840 and 2410158401015840 XKing tyres suggesting that tyre sizecould have considerable effect on performance
While difficult to glean conclusive data regarding overallXCO-MTB performance from such a small downhill com-ponent of performance as collected in this study it is worthnoting that previous research has linked decreased vibrationexposure to increased efficiency [10 11] As such the attenu-ation of accelerations experienced (Figure 5 and Tables 3 and4) at the point of contact between human and bicycle (han-dlebar and seat post) as a result of increased tyre size couldtheoretically be connected to overall performance duringcomplete race distance This obviously assumes that the dec-rease in nonpropulsive work would reduce muscular andcognitive fatigue and consequentially increase performanceHowever it is acknowledged that a complete XCO-MTB raceentails a variety of surfaces and terrains where themajority oftime is spent cycling uphill on smoother surfaces that mightactually suit a smaller higher pressure tyre As such futureresearch is needed to explore this aspect
On the other hand tyre inflation pressure does not seemto influence performance in this experiment (Figure 4) eventhough an increase in accelerations in all axes (Figure 5)related to an increase in magnitude (Table 3) rather than fre-quency (Table 2) was apparent While interesting the tran-sient nature of the protocol used cannot corroborate thelong term effects that racing for ge90mins with the observedincreases in magnitude would have on accumulated muscu-lar fatigue Based on previous laboratorywork [6 19] it is beli-eved that XCO-MTB performance would be compromisedover a complete race distance but requires confirmation
Similar to previous work on the transference of acceler-ations during XCO-MTB [9] the data presented here showsthat both the bicycle and the soft tissue are dissipating energy[20 21] from the interaction of bicycle with surface terrainimplying a reduced nonpropulsive work component of XCO-MTB as a result of increased tyre size This is supportedthrough two-way interactions between both tyre size lowast accel-erometer position and tyre inflation pressure lowast accelero-meter location for total vertical and horizontal accelera-tions (Figure 5) magnitude (Table 3) and low-high powerdistribution (Table 4) As such the reduction in measuresassociated with acceleration exposure reported previouslydecreased at the point of interaction with the bicycle withan increase in tyre size Importantly this was accompaniedby reductions at the soft tissue sites implying a reduced non-propulsive work component of XCO-MTB as a result ofincreased tyre size Alternatively increases in tyre inflationpressure have the opposite and negative effect by increasingrider exposure to accelerations at the point of interface withbicycle and thus increase the non-propulsive componentAdditionally the controlled nature of this protocol mayenable participants to alter body position or riding style
dependent on tyre chracteristics not afforded during a racingsituation
5 Conclusion
This study set out to quantify the influence of tyre size andnormalised tyre inflation pressure on exposure to impactstypical to cross country mountain bike riding It was foundthat the larger the tyre size within the range tested thelower the level of impact exposure experienced at the pointof contact between bicycle and body This reduction meantparticipants performed less non-propulsive muscular workand performed better when compared to a smaller tyre of thesame construction and tread pattern Contrariwise highertyre inflation pressures were associated with an increase inthe level of impact exposure and thus greater soft tissue workin order to attenuate the larger impacts In addition it wasshown that increased tyre inflation pressure could interactnegatively with tyre size while increased tyre size couldinteract positively with tyre inflation pressure As such theeffects of reduced exposure need to be assessed with regardsto longer periods of time such as experienced in a mountainbike race or recreational ride
6 Practical Application
It is recommended that participants (recreational and com-petitive) use a higher volume tyre over any smaller alternativewithin the range tested here In doing so it is suggested thatparticipants could improve performance and likely reducethe risk of overuse injuries or increase the time spent ridingfor the same risk(s)
It is important to note that two-way interactions betweentyre size and tyre inflation pressures suggest that the benefitsof riding with a bigger tyre could be negated through the useof high tyre inflation pressure Conversely the use of lowertyre inflation pressures in smaller tyres could reduce exposurebut must come with a warning of increased unreliability interms of punctures and de-beading from the wheel rim
7 Future Research
The findings of this study must now be verified over a com-plete XCO-MTB race lap consisting of a variety of terrainsto enable whole performance analysis and terrain specificsection performance analysis
Conflict of Interests
The authors declare that there is no conflict of interestsregarding the publication of this paper
References
[1] H THurst and S Atkins ldquoPower output of field-based downhillmountain bikingrdquo Journal of Sports Sciences vol 24 no 10 pp1047ndash1053 2006
[2] F M Impellizzeri and S M Marcora ldquoThe physiology ofmountain bikingrdquo SportsMedicine vol 37 no 1 pp 59ndash71 2007
10 Shock and Vibration
[3] P W Macdermid and S Stannard ldquoMechanical work andphysiological responses to simulated cross country mountainbike racingrdquo Journal of Sports Sciences vol 30 no 14 pp 1491ndash1501 2012
[4] B Stapelfeldt A Schwirtz Y O Schumacher and M Hille-brecht ldquoWorkload demands in mountain bike racingrdquo Interna-tional Journal of Sports Medicine vol 25 no 4 pp 294ndash3002004
[5] P Macdermid P Fink and S Stannard ldquoThe effects of vibra-tions experienced during road vs off-road cyclingrdquo Interna-tional Journal of Sports Medicine 2015
[6] B Samuelson L Jorfeldt and B Ahlborg ldquoInfluence of vibra-tion on endurance of maximal isometric contractionrdquo ClinicalPhysiology vol 9 no 1 pp 21ndash25 1989
[7] J Titlestad A Fairlie-Clarke M Davie A Whittaker and SGrant ldquoExperimental evaluation of mountain bike suspensionsystemsrdquo Acta Polytechnica vol 43 no 5 2003
[8] H T Hurst M Swaren K Hebert-Losier et al ldquoInfluenceof course type on upper body muscle activity in elite Cross-Country andDownhillmountain bikers during offRoadDown-hill Cyclingrdquo Journal of Science and Cycling vol 1 no 2 pp 2ndash92012
[9] P W Macdermid P W Fink and S R Stannard ldquoTransferenceof 3D accelerations during cross country mountain bikingrdquoJournal of Biomechanics vol 47 no 8 pp 1829ndash1837 2014
[10] P W Macdermid P W Fink and S R Stannard ldquoThe effectsof vibrations experienced during road vs off-road cyclingrdquoInternational Journal of Sports Medicine 2015
[11] J Mester P Spitzenfeil J Schwarzer and F Seifriz ldquoBiologicalreaction to vibrationmdashimplications for sportrdquo Journal of Scienceand Medicine in Sport vol 2 no 3 pp 211ndash226 1999
[12] T Ishii Y Umerura and K Kitagawa ldquoInfluences of mountainbike suspension systems on energy supply and performancerdquoJapanese Journal of Biomechanics in Sports and Exercise vol 7pp 2ndash9 2003
[13] L M Sherwin P M O Owende C L Kanali J Lyons and SM Ward ldquoInfluence of tyre inflation pressure on whole-bodyvibrations transmitted to the operator in a cut-to-length timberharvesterrdquoApplied Ergonomics vol 35 no 3 pp 253ndash261 2004
[14] J Gordon J J Kauzlarich and J G Thacker ldquoTests of two newpolyurethane foam wheelchair tiresrdquo Journal of RehabilitationResearch and Development vol 26 no 1 pp 33ndash46 1989
[15] B J Sawatzky W O Kim and I Denison ldquoThe ergonomics ofdifferent tyres and tyre pressure during wheelchair propulsionrdquoErgonomics vol 47 no 14 pp 1475ndash1483 2004
[16] PWMacdermid PW Fink and S R Stannard ldquoThe influenceof tyre characteristics on measures of rolling performance dur-ing cross-country mountain bikingrdquo Journal of Sports Sciencesvol 33 no 3 pp 277ndash285 2015
[17] R Van der Plas Bicycle Technology Motorbooks International1991
[18] M Munera X Chiementin S Crequy and W Bertucci ldquoPhys-ical risk associated with vibration at cyclingrdquo Mechanics ampIndustry vol 15 no 6 pp 535ndash540 2014
[19] J Titlestad T Fairlie-Clarke A Whittaker M Davie I Wattand S Grant ldquoEffect of suspension systems on the physiologicaland psychological responses to sub-maximal biking on simu-lated smoothand bumpy tracksrdquo Journal of Sports Sciences vol24 no 2 pp 125ndash135 2006
[20] V B Issurin ldquoVibrations and their applications in sport areviewrdquo Journal of Sports Medicine and Physical Fitness vol 45no 3 pp 324ndash336 2005
[21] M Levy and G A Smith ldquoEffectiveness of vibration dampingwith bicycle suspension systemsrdquo Sports Engineering vol 8 no2 pp 99ndash106 2005
International Journal of
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VLSI Design
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Shock and Vibration
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Civil EngineeringAdvances in
Acoustics and VibrationAdvances in
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Volume 2014
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International Journal of
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Navigation and Observation
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DistributedSensor Networks
International Journal of
4 Shock and Vibration
Low High0
1
2
3
4
5
ModerateNormalized tyre pressure
Tim
e (s)
CX (35mm)22 (55mm)24 (60mm)
lowastlowastlowastlowast
++++++++ ++++
+++++++ +++nabla
Figure 4 Mean plusmn SD for performance time (s) over the trialprotocol (Figure 1) lowastlowastlowastlowast(119875 lt 00001) main effect of tyre post hocdifferences when comparing tyres for within-tyre inflation pressureswhen compared to CX ++++(119875 lt 00001) +++(119875 lt 0001) and 22nabla(119875 lt 005)
inflation pressure (119875 lt 005) between pressure low andmoderate (95 CI minus1261ndashminus0066) low and high (95 CIminus2724ndashminus1529) and moderate and high (95 CI minus2060ndashminus0866) Multiple comparisons between the accelerometerlocations were significantly different (119875 lt 00001) except inthe case of the handlebar and seat post (119875 = 0824 95 CIminus0360ndash1714) and the lower back and forehead (119875 = 009295 CI minus0069ndash2005)
Significant main effects for vertical acceleration ampli-tude (RMS) for tyre size (119865
(233)= 16010 119875 lt 00001) tyre
inflation pressure (119865(233)= 17319 119875 lt 00001) and accel-
erometer location (119865(566)= 26543 119875 lt 00001) were found
(Figures 5(d)ndash5(f)) There were significant interactions bet-ween tyre size and accelerometer location (119865
(799)= 4657
119875 lt 00001) and tyre inflation pressure and accelerometerlocation (119865
(799)= 4253 119875 lt 00001) Post hoc analysis
showed significant differences (119875 lt 00001) for tyre sizebetween cycloXKing and 22 XKing (95 CI 0360ndash1163)and cycloXKing and 24 XKing (95 CI 0466ndash1270)normalised tyre inflation pressure between low and high(95 CI minus1347ndashminus05440) and moderate and high (95 CIminus01666ndash0637) Multiple comparisons between accelerome-ter locations were significantly different (119875 lt 001) except inthe case of the handlebar and wrist (119875 = 1000) and lowerback and forehead (119875 = 1000)
Horizontal accelerations (Figures 5(g)ndash5(i)) showedmaineffects for tyre size (119865
(233)= 35895 119875 lt 00001) tyre infla-
tion pressure (119865(233)= 10460 119875 lt 00001) and accelero-
meter location (119865(566)= 1548645 119875 lt 00001) with inter-
actions between tyre size lowast tyre inflation pressure (119865(466)=
3111 119875 = 00150) tyre size lowast accelerometer location(119865(799)= 10116 119875 lt 00001) and tyre inflation pressure lowast
accelerometer location (119865(799)= 1866 119875 = 00470) Post
hoc analysis identified differences between all tyre sizes (119875 lt001) between tyre inflation pressures low and high (119875 lt00001) and moderate and high (119875 = 00109) and betweenall accelerometer locations (119875 lt 005)
Three-way ANOVA of spectral analysis maximum fre-quency (Table 2) data provided a significant interactionbetween tyre size and accelerometer location (119865
(799)= 6700
119875 lt 00001) with a main effect of tyre size (119865(233)= 12553
119875 lt 00001) and accelerometer location (119865(566)= 51011 119875 lt
00001) Post hoc analysis identified differences between tyresizes cycloXKing and 22 XKing (95 CI minus02865ndashminus07662)and cycloXKing and 24 XKing (95 CI minus03017ndashminus00919)Data for maximummagnitude (Table 3) identified significantmain effects for tyre size (119865
(233)= 34420 119875 lt 00001)
tyre inflation pressure (119865(233)= 22864 119875 lt 00001) and
acceleration position (119865(566)= 3336605 119875 lt 00001) with
interactions between tyre size lowast accelerometer position(119865(799)= 10852 119875 lt 00001) and tyre inflation pressure lowast
accelerometer location (119865(799)= 4271 119875 lt 00001) Post hoc
analysis showed differences between tyre sizes occurred forcycloXKing and 2210158401015840 Xking (119875 = 00050) cycloXKing and2410158401015840 XKing (119875 lt 00001) and 2210158401015840 XKing and 2410158401015840 XKing(119875 lt 00001) tyre inflation pressure differences occurredbetween low and moderate (119875 = 0026) low and high(119875 lt 00001) and moderate and high (119875 = 00002) whiledifferences between all accelerometer positions (119875 lt 00500)except lower back and forehead (119875 gt 00500) occurred
Power data separated for low (lt5Hz) frequency (Table 4)identified significantmain effects for tyre size (119865
(233)= 5157
119875 = 00060) and accelerometer position (119865(566)= 1855902
119875 lt 00001) interactions between tyre size and accelerometerposition (119865
(799)= 1990 119875 = 00320) and tyre inflation pres-
sure and accelerometer position (119865(799)= 1998 119875 = 00310)
Post hoc differences for tyre size between cycloXKing and2210158401015840 XKing (95 CI minus04853ndashminus00693 119875 = 00040) werepresent and all accelerometer positions except the handlebarand seat post (119875 = 06330) High (gt5Hz) frequency (Table 4)showed significant main effects for tyre inflation pressure(119865(233)= 17516 119875 lt 00001) and accelerometer position
(119865(566)= 5190764 119875 lt 00001) with interactions for tyre
sizelowast tyre inflation pressure (119865(466)= 4210119875 = 00020) tyre
size lowast accelerometer position (119865(799)= 9575 119875 = 00070)
and tyre inflation pressure lowast accelerometer position (119865(799)=
2091 119875 = 00230) Post hoc analysis identified differenceswithin the tyre inflation factor between low andhigh pressure(95 CI minus15404ndashminus06302 119875 lt 00001) and moderate andhigh pressure (95 CI minus12441ndashminus03339 119875 lt 00001) Allaccelerometer positions were different (119875 lt 00001) exceptin the case of the handlebar and wrist (119875 = 07560) and thelower back and head (119875 = 10000)
4 Discussion
The aim of this study was to quantify the influence of tyresize and the normalised tyre inflation pressure on exposureto impacts and their interactions typical of that experiencedwhilst riding on a cross countrymountain bike trailThemainfindings were as follows (a) increases in tyre size led to
Shock and Vibration 5
Han
dleb
ar
Wris
t
Ank
le
Seat
pos
t
Lum
bar
Hea
d
Han
dleb
ar
Wris
t
Ank
le
Seat
pos
t
Lum
bar
Hea
d
Han
dleb
ar
Wris
t
Ank
le
Seat
pos
t
Lum
bar
Hea
d
Han
dleb
ar
Wris
t
Ank
le
Seat
pos
t
Lum
bar
Hea
d
Han
dleb
ar
Wris
t
Ank
le
Seat
pos
t
Lum
bar
Hea
d
Han
dleb
ar
Wris
t
Ank
le
Seat
pos
t
Lum
bar
Hea
d
Han
dleb
ar
Wris
t
Ank
le
Seat
pos
t
Lum
bar
Hea
d
Han
dleb
ar
Wris
t
Ank
le
Seat
pos
t
Lum
bar
Hea
d
Han
dleb
ar
Wris
t
Ank
le
Seat
pos
t
Lum
bar
Hea
d
(a) (b) (c)
(d) (e) (f)
(g) (h) (i)Normalised tyre inflation pressure Normalised tyre inflation pressure Normalised tyre inflation pressure
Low Moderate High
Acce
lera
tion
axis
Acce
lera
tion
axis
Acce
lera
tion
axis
Hor
izon
tal
Vert
ical
Tota
l
0102030405060
Acce
lera
tion
(mmiddotsminus
2)
0102030405060
Acce
lera
tion
(mmiddotsminus
2)
0102030405060
Acce
lera
tion
(mmiddotsminus
2)
0102030405060
Acce
lera
tion
(mmiddotsminus
2)
0102030405060
Acce
lera
tion
(mmiddotsminus
2)
0102030405060
Acce
lera
tion
(mmiddotsminus
2)
0102030405060
Acce
lera
tion
(mmiddotsminus
2)
0102030405060
Acce
lera
tion
(mmiddotsminus
2)
0102030405060
Acce
lera
tion
(mmiddotsminus
2)
Accelerometer position Accelerometer position Accelerometer position
poundpoundpoundpoundlowastlowast $$$$ otimesotimesotimesotimes nablanablanablanabla emptyemptyemptyempty
poundpoundpoundpound $$$$ otimesotimesotimesotimes nablanablanablanabla emptyemptyemptyempty
lowastlowastlowastlowast otimesotimesotimesotimes nablanablanablanabla emptyemptyemptyempty
Figure 5 Comparison between tyres (CycloXKing (black bar) 22 XKing (gray bar) and 24 XKing (white bar)) and three normalisedtyre inflation pressures characterised as low (1) normal (2) and high (3) for (a)ndash(c) Total accelerations (d)ndash(f) Vertical accelerations (g)ndash(i) Horizontal accelerations where lowast refers to the interaction for tyre size lowast tyre pressure (lowastlowastlowastlowast119875 lt 00001 lowastlowast119875 lt 001) $ refers to theinteraction for tyre sizelowast accelerometer location ($$$$119875 lt 00001) m refers to the interaction for tyre pressurelowast accelerometer location (mmmm119875 lt00001) otimesotimesotimesotimes(119875 lt 00001)main effect of tyre size OslashOslashOslashOslash(119875 lt 00001)main effect of tyre pressure nablanablanablanabla(119875 lt 00001)main effect of accelerometerlocation
positive effects on performance compared to tyre inflationpressure when riding down rough terrain (b) increases intyre size decrease the level of impact exposure experienced atpoint of contact(s) with the bicycle and thus reduce nonprop-ulsive work load (c) increased tyre inflation pressure intensi-fies exposure to acceleration exposure
Increased exposure to impacts and vibrations associatedwith forwards momentum of an off-road cyclist are linked toincreased nonpropulsive work [8] decreased efficiency [11]and performance [6 7] The reduction of this nonpropulsivework is thus potentially important with regard to competitiveperformance and theminimisation of overuse injury risk [18]
6 Shock and Vibration
Table2MeanplusmnSD
form
axim
umfre
quency
(Hz)of
acceleratio
nsdu
ringthetria
lseparatedfora
ccelerom
eter
locatio
ntyre
sizeandtyre
inflatio
npressure
Accelerometer
position
Cyclo
XKingtyreclubsclubsclubsclubs
2210158401015840XK
ingtyre
2410158401015840XK
ingtyre
3-way
ANOVA
LowPS
IMod
PSI
HighPS
ILo
wPS
IMod
PSI
HighPS
ILo
wPS
IMod
PSI
HighPS
IHandlebar
05284plusmn0049
05084plusmn004
605099plusmn006
005659plusmn0043
05632plusmn0036
05526plusmn0036
05781plusmn0029
060
03plusmn0055
05565plusmn0032
Tyrelowastlowastlowastlowast
PSIN
S
ALoclowastlowastlowastlowast
TyrelowastALoclowastlowastlowastlowast
Wris
t05284plusmn0049
05084plusmn004
605099plusmn006
005659plusmn0043
05632plusmn0037
05526plusmn0037
05781plusmn0029
060
03plusmn0055
05787plusmn0076
Ank
le05284plusmn0049
05084plusmn004
605099plusmn006
005659plusmn0043
05632plusmn0037
05526plusmn0036
05781plusmn0029
060
03plusmn0055
05787plusmn0032
Seatpo
st05284plusmn0049
05088plusmn0036
05099plusmn0036
05659plusmn0043
05654plusmn0036
05539plusmn0036
05781plusmn0029
060
03plusmn0055
05565plusmn0032
Lumbarotimesotimesotimesotimes
08372plusmn0760
08165plusmn0756
05345plusmn0123
13076plusmn1168
18315plusmn10
3416
682plusmn14
5320180plusmn14
2113
681plusmn
1034
14722plusmn1166
Forehead
05749plusmn0259
05088plusmn004
605099plusmn006
006518plusmn0284
05202plusmn0123
05098plusmn0121
05749plusmn0030
060
49plusmn0051
05117plusmn0117
Tyre(ty
resiz
e)PSI
(tyreinflatio
npressure)andALoc
(accelerom
eter
position)
refertothem
aineffectfor
maxim
umfre
quencyTyrelowast
ALoc
refersto
thetwo-way
interactionbetweentyresiz
eand
accelerometer
position
NSdeno
tesa
nonsignificanteffect(119875gt0005)lowastlowastlowastlowast(119875lt00001)clubsclubsclubsclubssig
nifiesa
postho
cdifference
(119875lt00001)for
tyre
sizew
hencomparin
gcyclo
XKingto
both
2210158401015840and2410158401015840XK
ingtyreotimesotimesotimesotimes
signifiesa
postho
cdifference
(119875lt00001)for
accelerometer
positionwhencomparedto
allother
accelerometer
positions
Shock and Vibration 7
Table3MeanplusmnSD
form
axim
ummagnitude
(g2 )of
acceleratio
nsdu
ringthetria
lseparatedfora
ccelerom
eter
locatio
ntyre
sizeandtyre
inflatio
npressure
Accelerometer
position
Cyclo
XKingtyre
2210158401015840XK
ingtyreclubsclubs
2410158401015840XK
ingtyreclubsclubsclubsclubs
3-way
ANOVA
LowPS
IMod
PSIoplus
HighPS
Ioplusoplus
LowPS
IMod
PSIoplus
HighPS
Ioplusoplus
LowPS
IMod
PSIoplus
HighPS
Ioplusoplus
Handlebar
96649plusmn0483
98169plusmn0837
99169plusmn0394
91121plusmn
0572
95915plusmn040
799
974plusmn0523
860
00plusmn076591403plusmn0489
96618plusmn0356
Tyrelowastlowastlowastlowast
PSIlowastlowastlowastlowast
ALoclowastlowastlowastlowast
TyrelowastALoclowastlowastlowastlowast
PSIlowast
ALoclowastlowastlowastlowast
Wris
t89805plusmn0969
92501plusmn
1016
93962plusmn0698
84191plusmn0744
86780plusmn0770
91158plusmn0944
80720plusmn0897
88992plusmn10
9285109plusmn0374
Ank
le104872plusmn0882106966plusmn12
44108250plusmn0903
90277plusmn13
9991
134plusmn0990
1015
14plusmn0970
86496plusmn14
3174
320plusmn0793
95862plusmn1127
Seatpo
st85581plusmn0596
88560plusmn10
0988657plusmn0831
85843plusmn10
9791
929plusmn0997
95898plusmn0936
81989plusmn14
0789681plusmn13
7592
576plusmn0977
Lumbar
09245plusmn0201
10165plusmn0315
09747plusmn0279
09550plusmn0198
09176plusmn0129
09810plusmn0169
08461plusmn0094
09134plusmn0124
09347plusmn0138
Forehead
12333plusmn0265
11829plusmn0106
12301plusmn
0220
10693plusmn
0184
11935plusmn0218
11763plusmn0147
11001plusmn
0150
10876plusmn0210
11283plusmn0244
Tyre(ty
resiz
e)PSI
(tyreinflatio
npressure)andALoc
(accelerom
eter
position)
refertothem
aineffectfor
maxim
umfre
quencyTyrelowast
ALoc
refersto
thetwo-way
interactionbetweentyresiz
eand
accelerometer
position
NSdeno
tesa
nonsignificanteffect(119875gt0005)lowastlowastlowastlowast(119875lt00001)clubsclubsclubsclubssig
nifiesa
postho
cdifference
(119875lt00001)a
ndclubsclubs(119875lt001)for
tyre
sizew
hencomparedto
cyclo
XKingtyreotimesotimesotimesotimessig
nifiesa
postho
cdifference
(119875lt00001)otimesandoplus(119875lt005)for
tyre
inflatio
npressure
whencomparedto
LowPS
Iandoplusoplus(119875lt0001)com
paredto
Mod
PSI
8 Shock and Vibration
Table4MeanplusmnSD
form
ovem
entsseparatedforlow
(lt5H
z)andhigh
(gt5H
z)po
wer
Accelerometer
position
Cyclo
Xkingtyre
2210158401015840XK
ingtyreclubsclubs
2410158401015840XK
ingtyre
3-way
ANOVA
LowPS
IMod
PSI
HighPS
ILo
wPS
IMod
PSIoplusoplusoplusoplus
HighPS
ILo
wPS
IMod
PSI
HighPS
Iotimesotimesotimesotimes
Lowpo
wer
hand
lebar
76020plusmn0372
73377plusmn0730
73461plusmn
0722
79999plusmn0706
80373plusmn0601
78545plusmn066
777
180plusmn0535
81915plusmn0921
73545plusmn0496
Tyrelowastlowastlowast
ALoclowastlowastlowastlowast
TyrelowastALoclowast
PSIlowast
ALoclowast
Wris
t1110
12plusmn14
331110
16plusmn0798
108242plusmn0665112274plusmn0783
113173plusmn0791
111153plusmn0940
107093plusmn0831
112719plusmn1111
1117
09plusmn14
81Ank
le88034plusmn12
8687661plusmn15
7491
143plusmn15
0485389plusmn15
5685304plusmn13
6793
778plusmn12
2886588plusmn18
5177
914plusmn0866
89735plusmn15
55Seatpo
st70
221plusmn
0892
69096plusmn1130
69559plusmn1100
77862plusmn0844
7740
8plusmn0802
76287plusmn0682
74695plusmn0979
81789plusmn15
9575
053plusmn0870
Lumbar
22323plusmn0428
22711plusmn0431
22088plusmn0555
23851plusmn0393
23896plusmn0385
24398plusmn0512
21917plusmn0240
21500plusmn0199
22178plusmn0242
Forehead
16805plusmn0125
15723plusmn0205
16235plusmn0241
17659plusmn0225
17505plusmn0263
15788plusmn0168
17763plusmn046
016
319plusmn0482
16620plusmn0461
Highpo
wer
hand
lebar
309527plusmn10
84316942plusmn2200
319095plusmn1144
313476plusmn16
95325003plusmn2085328681plusmn
1642
309170plusmn2816
325744plusmn2808338956plusmn2025PS
Ilowastlowastlowastlowast
ALoclowastlowastlowastlowast
TyrelowastPS
Ilowastlowast
TyrelowastALoclowastlowast
PSIlowast
ALoclowast
Wris
t310326plusmn17
613118
62plusmn19
44319101plusmn
1745
308851plusmn
1646
307399plusmn15
88324736plusmn18
583110
31plusmn16
343252
17plusmn2201
320763plusmn10
01Ank
le320164plusmn2753
307261plusmn
1813
308363plusmn19
35294291plusmn
1562
297999plusmn19
623119
27plusmn1746
299579plusmn4112
287204plusmn1748
3252
10plusmn2184
Seatpo
st343183plusmn2782
339910plusmn2618
3374
90plusmn19
463114
56plusmn2294324106plusmn204
8339546plusmn19
09306605plusmn4610324129plusmn356434364
6plusmn2565
Lumbar
540
80plusmn12
6055831plusmn0971
544
96plusmn1139
53255plusmn13
3454598plusmn12
1254818plusmn12
1248842plusmn0432
46912plusmn0481
53320plusmn0485
Forehead
55814plusmn13
9762502plusmn0620
58694plusmn0998
49398plusmn10
8350786plusmn14
2353796plusmn1525
57876plusmn1741
46845plusmn0808
59633plusmn15
70Where
tyre
(tyre
size)P
SI(ty
reinflatio
npressure)andALoc
(accele
rometer
locatio
n)refertothem
aineffectfor
power
band
Tyrelowast
ALoc
refersto
thetwo-way
interactionbetweentyre
sizea
ndaccelerometer
locatio
nlowastdeno
tessignificance
(119875lt005)lowastlowast(119875lt001)lowastlowastlowast(119875lt0001)lowastlowastlowastlowast(119875lt00001)clubsclubssig
nifiesa
postho
cdifference
(119875lt001)for
lowpo
wer
whencomparedto
cyclo
XKingtyre
sizeotimesotimesotimesotimessig
nifiesa
postho
cdifference
(119875lt00001)for
tyre
inflatio
npressure
whencomparedto
LowPS
Iandoplusoplusoplusoplus(119875lt00001)com
paredto
HighPS
I
Shock and Vibration 9
In the first instance Figure 4 identifies the highly signifi-cant (119875 lt 00001) effect of tyre size on performance timewithregard to normalised tyre inflation pressures This is furtherexacerbated considering the typical tyre inflation pressure(moderate Figure 3) used by competitive XCO-MTB athletes[16] At this pressure post hoc analysis identified differencesbetween 2210158401015840 and 2410158401015840 XKing tyres suggesting that tyre sizecould have considerable effect on performance
While difficult to glean conclusive data regarding overallXCO-MTB performance from such a small downhill com-ponent of performance as collected in this study it is worthnoting that previous research has linked decreased vibrationexposure to increased efficiency [10 11] As such the attenu-ation of accelerations experienced (Figure 5 and Tables 3 and4) at the point of contact between human and bicycle (han-dlebar and seat post) as a result of increased tyre size couldtheoretically be connected to overall performance duringcomplete race distance This obviously assumes that the dec-rease in nonpropulsive work would reduce muscular andcognitive fatigue and consequentially increase performanceHowever it is acknowledged that a complete XCO-MTB raceentails a variety of surfaces and terrains where themajority oftime is spent cycling uphill on smoother surfaces that mightactually suit a smaller higher pressure tyre As such futureresearch is needed to explore this aspect
On the other hand tyre inflation pressure does not seemto influence performance in this experiment (Figure 4) eventhough an increase in accelerations in all axes (Figure 5)related to an increase in magnitude (Table 3) rather than fre-quency (Table 2) was apparent While interesting the tran-sient nature of the protocol used cannot corroborate thelong term effects that racing for ge90mins with the observedincreases in magnitude would have on accumulated muscu-lar fatigue Based on previous laboratorywork [6 19] it is beli-eved that XCO-MTB performance would be compromisedover a complete race distance but requires confirmation
Similar to previous work on the transference of acceler-ations during XCO-MTB [9] the data presented here showsthat both the bicycle and the soft tissue are dissipating energy[20 21] from the interaction of bicycle with surface terrainimplying a reduced nonpropulsive work component of XCO-MTB as a result of increased tyre size This is supportedthrough two-way interactions between both tyre size lowast accel-erometer position and tyre inflation pressure lowast accelero-meter location for total vertical and horizontal accelera-tions (Figure 5) magnitude (Table 3) and low-high powerdistribution (Table 4) As such the reduction in measuresassociated with acceleration exposure reported previouslydecreased at the point of interaction with the bicycle withan increase in tyre size Importantly this was accompaniedby reductions at the soft tissue sites implying a reduced non-propulsive work component of XCO-MTB as a result ofincreased tyre size Alternatively increases in tyre inflationpressure have the opposite and negative effect by increasingrider exposure to accelerations at the point of interface withbicycle and thus increase the non-propulsive componentAdditionally the controlled nature of this protocol mayenable participants to alter body position or riding style
dependent on tyre chracteristics not afforded during a racingsituation
5 Conclusion
This study set out to quantify the influence of tyre size andnormalised tyre inflation pressure on exposure to impactstypical to cross country mountain bike riding It was foundthat the larger the tyre size within the range tested thelower the level of impact exposure experienced at the pointof contact between bicycle and body This reduction meantparticipants performed less non-propulsive muscular workand performed better when compared to a smaller tyre of thesame construction and tread pattern Contrariwise highertyre inflation pressures were associated with an increase inthe level of impact exposure and thus greater soft tissue workin order to attenuate the larger impacts In addition it wasshown that increased tyre inflation pressure could interactnegatively with tyre size while increased tyre size couldinteract positively with tyre inflation pressure As such theeffects of reduced exposure need to be assessed with regardsto longer periods of time such as experienced in a mountainbike race or recreational ride
6 Practical Application
It is recommended that participants (recreational and com-petitive) use a higher volume tyre over any smaller alternativewithin the range tested here In doing so it is suggested thatparticipants could improve performance and likely reducethe risk of overuse injuries or increase the time spent ridingfor the same risk(s)
It is important to note that two-way interactions betweentyre size and tyre inflation pressures suggest that the benefitsof riding with a bigger tyre could be negated through the useof high tyre inflation pressure Conversely the use of lowertyre inflation pressures in smaller tyres could reduce exposurebut must come with a warning of increased unreliability interms of punctures and de-beading from the wheel rim
7 Future Research
The findings of this study must now be verified over a com-plete XCO-MTB race lap consisting of a variety of terrainsto enable whole performance analysis and terrain specificsection performance analysis
Conflict of Interests
The authors declare that there is no conflict of interestsregarding the publication of this paper
References
[1] H THurst and S Atkins ldquoPower output of field-based downhillmountain bikingrdquo Journal of Sports Sciences vol 24 no 10 pp1047ndash1053 2006
[2] F M Impellizzeri and S M Marcora ldquoThe physiology ofmountain bikingrdquo SportsMedicine vol 37 no 1 pp 59ndash71 2007
10 Shock and Vibration
[3] P W Macdermid and S Stannard ldquoMechanical work andphysiological responses to simulated cross country mountainbike racingrdquo Journal of Sports Sciences vol 30 no 14 pp 1491ndash1501 2012
[4] B Stapelfeldt A Schwirtz Y O Schumacher and M Hille-brecht ldquoWorkload demands in mountain bike racingrdquo Interna-tional Journal of Sports Medicine vol 25 no 4 pp 294ndash3002004
[5] P Macdermid P Fink and S Stannard ldquoThe effects of vibra-tions experienced during road vs off-road cyclingrdquo Interna-tional Journal of Sports Medicine 2015
[6] B Samuelson L Jorfeldt and B Ahlborg ldquoInfluence of vibra-tion on endurance of maximal isometric contractionrdquo ClinicalPhysiology vol 9 no 1 pp 21ndash25 1989
[7] J Titlestad A Fairlie-Clarke M Davie A Whittaker and SGrant ldquoExperimental evaluation of mountain bike suspensionsystemsrdquo Acta Polytechnica vol 43 no 5 2003
[8] H T Hurst M Swaren K Hebert-Losier et al ldquoInfluenceof course type on upper body muscle activity in elite Cross-Country andDownhillmountain bikers during offRoadDown-hill Cyclingrdquo Journal of Science and Cycling vol 1 no 2 pp 2ndash92012
[9] P W Macdermid P W Fink and S R Stannard ldquoTransferenceof 3D accelerations during cross country mountain bikingrdquoJournal of Biomechanics vol 47 no 8 pp 1829ndash1837 2014
[10] P W Macdermid P W Fink and S R Stannard ldquoThe effectsof vibrations experienced during road vs off-road cyclingrdquoInternational Journal of Sports Medicine 2015
[11] J Mester P Spitzenfeil J Schwarzer and F Seifriz ldquoBiologicalreaction to vibrationmdashimplications for sportrdquo Journal of Scienceand Medicine in Sport vol 2 no 3 pp 211ndash226 1999
[12] T Ishii Y Umerura and K Kitagawa ldquoInfluences of mountainbike suspension systems on energy supply and performancerdquoJapanese Journal of Biomechanics in Sports and Exercise vol 7pp 2ndash9 2003
[13] L M Sherwin P M O Owende C L Kanali J Lyons and SM Ward ldquoInfluence of tyre inflation pressure on whole-bodyvibrations transmitted to the operator in a cut-to-length timberharvesterrdquoApplied Ergonomics vol 35 no 3 pp 253ndash261 2004
[14] J Gordon J J Kauzlarich and J G Thacker ldquoTests of two newpolyurethane foam wheelchair tiresrdquo Journal of RehabilitationResearch and Development vol 26 no 1 pp 33ndash46 1989
[15] B J Sawatzky W O Kim and I Denison ldquoThe ergonomics ofdifferent tyres and tyre pressure during wheelchair propulsionrdquoErgonomics vol 47 no 14 pp 1475ndash1483 2004
[16] PWMacdermid PW Fink and S R Stannard ldquoThe influenceof tyre characteristics on measures of rolling performance dur-ing cross-country mountain bikingrdquo Journal of Sports Sciencesvol 33 no 3 pp 277ndash285 2015
[17] R Van der Plas Bicycle Technology Motorbooks International1991
[18] M Munera X Chiementin S Crequy and W Bertucci ldquoPhys-ical risk associated with vibration at cyclingrdquo Mechanics ampIndustry vol 15 no 6 pp 535ndash540 2014
[19] J Titlestad T Fairlie-Clarke A Whittaker M Davie I Wattand S Grant ldquoEffect of suspension systems on the physiologicaland psychological responses to sub-maximal biking on simu-lated smoothand bumpy tracksrdquo Journal of Sports Sciences vol24 no 2 pp 125ndash135 2006
[20] V B Issurin ldquoVibrations and their applications in sport areviewrdquo Journal of Sports Medicine and Physical Fitness vol 45no 3 pp 324ndash336 2005
[21] M Levy and G A Smith ldquoEffectiveness of vibration dampingwith bicycle suspension systemsrdquo Sports Engineering vol 8 no2 pp 99ndash106 2005
International Journal of
AerospaceEngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
RoboticsJournal of
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Active and Passive Electronic Components
Control Scienceand Engineering
Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
International Journal of
RotatingMachinery
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporation httpwwwhindawicom
Journal ofEngineeringVolume 2014
Submit your manuscripts athttpwwwhindawicom
VLSI Design
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Shock and Vibration
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Civil EngineeringAdvances in
Acoustics and VibrationAdvances in
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Electrical and Computer Engineering
Journal of
Advances inOptoElectronics
Hindawi Publishing Corporation httpwwwhindawicom
Volume 2014
The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014
SensorsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Modelling amp Simulation in EngineeringHindawi Publishing Corporation httpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Chemical EngineeringInternational Journal of Antennas and
Propagation
International Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Navigation and Observation
International Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
DistributedSensor Networks
International Journal of
Shock and Vibration 5
Han
dleb
ar
Wris
t
Ank
le
Seat
pos
t
Lum
bar
Hea
d
Han
dleb
ar
Wris
t
Ank
le
Seat
pos
t
Lum
bar
Hea
d
Han
dleb
ar
Wris
t
Ank
le
Seat
pos
t
Lum
bar
Hea
d
Han
dleb
ar
Wris
t
Ank
le
Seat
pos
t
Lum
bar
Hea
d
Han
dleb
ar
Wris
t
Ank
le
Seat
pos
t
Lum
bar
Hea
d
Han
dleb
ar
Wris
t
Ank
le
Seat
pos
t
Lum
bar
Hea
d
Han
dleb
ar
Wris
t
Ank
le
Seat
pos
t
Lum
bar
Hea
d
Han
dleb
ar
Wris
t
Ank
le
Seat
pos
t
Lum
bar
Hea
d
Han
dleb
ar
Wris
t
Ank
le
Seat
pos
t
Lum
bar
Hea
d
(a) (b) (c)
(d) (e) (f)
(g) (h) (i)Normalised tyre inflation pressure Normalised tyre inflation pressure Normalised tyre inflation pressure
Low Moderate High
Acce
lera
tion
axis
Acce
lera
tion
axis
Acce
lera
tion
axis
Hor
izon
tal
Vert
ical
Tota
l
0102030405060
Acce
lera
tion
(mmiddotsminus
2)
0102030405060
Acce
lera
tion
(mmiddotsminus
2)
0102030405060
Acce
lera
tion
(mmiddotsminus
2)
0102030405060
Acce
lera
tion
(mmiddotsminus
2)
0102030405060
Acce
lera
tion
(mmiddotsminus
2)
0102030405060
Acce
lera
tion
(mmiddotsminus
2)
0102030405060
Acce
lera
tion
(mmiddotsminus
2)
0102030405060
Acce
lera
tion
(mmiddotsminus
2)
0102030405060
Acce
lera
tion
(mmiddotsminus
2)
Accelerometer position Accelerometer position Accelerometer position
poundpoundpoundpoundlowastlowast $$$$ otimesotimesotimesotimes nablanablanablanabla emptyemptyemptyempty
poundpoundpoundpound $$$$ otimesotimesotimesotimes nablanablanablanabla emptyemptyemptyempty
lowastlowastlowastlowast otimesotimesotimesotimes nablanablanablanabla emptyemptyemptyempty
Figure 5 Comparison between tyres (CycloXKing (black bar) 22 XKing (gray bar) and 24 XKing (white bar)) and three normalisedtyre inflation pressures characterised as low (1) normal (2) and high (3) for (a)ndash(c) Total accelerations (d)ndash(f) Vertical accelerations (g)ndash(i) Horizontal accelerations where lowast refers to the interaction for tyre size lowast tyre pressure (lowastlowastlowastlowast119875 lt 00001 lowastlowast119875 lt 001) $ refers to theinteraction for tyre sizelowast accelerometer location ($$$$119875 lt 00001) m refers to the interaction for tyre pressurelowast accelerometer location (mmmm119875 lt00001) otimesotimesotimesotimes(119875 lt 00001)main effect of tyre size OslashOslashOslashOslash(119875 lt 00001)main effect of tyre pressure nablanablanablanabla(119875 lt 00001)main effect of accelerometerlocation
positive effects on performance compared to tyre inflationpressure when riding down rough terrain (b) increases intyre size decrease the level of impact exposure experienced atpoint of contact(s) with the bicycle and thus reduce nonprop-ulsive work load (c) increased tyre inflation pressure intensi-fies exposure to acceleration exposure
Increased exposure to impacts and vibrations associatedwith forwards momentum of an off-road cyclist are linked toincreased nonpropulsive work [8] decreased efficiency [11]and performance [6 7] The reduction of this nonpropulsivework is thus potentially important with regard to competitiveperformance and theminimisation of overuse injury risk [18]
6 Shock and Vibration
Table2MeanplusmnSD
form
axim
umfre
quency
(Hz)of
acceleratio
nsdu
ringthetria
lseparatedfora
ccelerom
eter
locatio
ntyre
sizeandtyre
inflatio
npressure
Accelerometer
position
Cyclo
XKingtyreclubsclubsclubsclubs
2210158401015840XK
ingtyre
2410158401015840XK
ingtyre
3-way
ANOVA
LowPS
IMod
PSI
HighPS
ILo
wPS
IMod
PSI
HighPS
ILo
wPS
IMod
PSI
HighPS
IHandlebar
05284plusmn0049
05084plusmn004
605099plusmn006
005659plusmn0043
05632plusmn0036
05526plusmn0036
05781plusmn0029
060
03plusmn0055
05565plusmn0032
Tyrelowastlowastlowastlowast
PSIN
S
ALoclowastlowastlowastlowast
TyrelowastALoclowastlowastlowastlowast
Wris
t05284plusmn0049
05084plusmn004
605099plusmn006
005659plusmn0043
05632plusmn0037
05526plusmn0037
05781plusmn0029
060
03plusmn0055
05787plusmn0076
Ank
le05284plusmn0049
05084plusmn004
605099plusmn006
005659plusmn0043
05632plusmn0037
05526plusmn0036
05781plusmn0029
060
03plusmn0055
05787plusmn0032
Seatpo
st05284plusmn0049
05088plusmn0036
05099plusmn0036
05659plusmn0043
05654plusmn0036
05539plusmn0036
05781plusmn0029
060
03plusmn0055
05565plusmn0032
Lumbarotimesotimesotimesotimes
08372plusmn0760
08165plusmn0756
05345plusmn0123
13076plusmn1168
18315plusmn10
3416
682plusmn14
5320180plusmn14
2113
681plusmn
1034
14722plusmn1166
Forehead
05749plusmn0259
05088plusmn004
605099plusmn006
006518plusmn0284
05202plusmn0123
05098plusmn0121
05749plusmn0030
060
49plusmn0051
05117plusmn0117
Tyre(ty
resiz
e)PSI
(tyreinflatio
npressure)andALoc
(accelerom
eter
position)
refertothem
aineffectfor
maxim
umfre
quencyTyrelowast
ALoc
refersto
thetwo-way
interactionbetweentyresiz
eand
accelerometer
position
NSdeno
tesa
nonsignificanteffect(119875gt0005)lowastlowastlowastlowast(119875lt00001)clubsclubsclubsclubssig
nifiesa
postho
cdifference
(119875lt00001)for
tyre
sizew
hencomparin
gcyclo
XKingto
both
2210158401015840and2410158401015840XK
ingtyreotimesotimesotimesotimes
signifiesa
postho
cdifference
(119875lt00001)for
accelerometer
positionwhencomparedto
allother
accelerometer
positions
Shock and Vibration 7
Table3MeanplusmnSD
form
axim
ummagnitude
(g2 )of
acceleratio
nsdu
ringthetria
lseparatedfora
ccelerom
eter
locatio
ntyre
sizeandtyre
inflatio
npressure
Accelerometer
position
Cyclo
XKingtyre
2210158401015840XK
ingtyreclubsclubs
2410158401015840XK
ingtyreclubsclubsclubsclubs
3-way
ANOVA
LowPS
IMod
PSIoplus
HighPS
Ioplusoplus
LowPS
IMod
PSIoplus
HighPS
Ioplusoplus
LowPS
IMod
PSIoplus
HighPS
Ioplusoplus
Handlebar
96649plusmn0483
98169plusmn0837
99169plusmn0394
91121plusmn
0572
95915plusmn040
799
974plusmn0523
860
00plusmn076591403plusmn0489
96618plusmn0356
Tyrelowastlowastlowastlowast
PSIlowastlowastlowastlowast
ALoclowastlowastlowastlowast
TyrelowastALoclowastlowastlowastlowast
PSIlowast
ALoclowastlowastlowastlowast
Wris
t89805plusmn0969
92501plusmn
1016
93962plusmn0698
84191plusmn0744
86780plusmn0770
91158plusmn0944
80720plusmn0897
88992plusmn10
9285109plusmn0374
Ank
le104872plusmn0882106966plusmn12
44108250plusmn0903
90277plusmn13
9991
134plusmn0990
1015
14plusmn0970
86496plusmn14
3174
320plusmn0793
95862plusmn1127
Seatpo
st85581plusmn0596
88560plusmn10
0988657plusmn0831
85843plusmn10
9791
929plusmn0997
95898plusmn0936
81989plusmn14
0789681plusmn13
7592
576plusmn0977
Lumbar
09245plusmn0201
10165plusmn0315
09747plusmn0279
09550plusmn0198
09176plusmn0129
09810plusmn0169
08461plusmn0094
09134plusmn0124
09347plusmn0138
Forehead
12333plusmn0265
11829plusmn0106
12301plusmn
0220
10693plusmn
0184
11935plusmn0218
11763plusmn0147
11001plusmn
0150
10876plusmn0210
11283plusmn0244
Tyre(ty
resiz
e)PSI
(tyreinflatio
npressure)andALoc
(accelerom
eter
position)
refertothem
aineffectfor
maxim
umfre
quencyTyrelowast
ALoc
refersto
thetwo-way
interactionbetweentyresiz
eand
accelerometer
position
NSdeno
tesa
nonsignificanteffect(119875gt0005)lowastlowastlowastlowast(119875lt00001)clubsclubsclubsclubssig
nifiesa
postho
cdifference
(119875lt00001)a
ndclubsclubs(119875lt001)for
tyre
sizew
hencomparedto
cyclo
XKingtyreotimesotimesotimesotimessig
nifiesa
postho
cdifference
(119875lt00001)otimesandoplus(119875lt005)for
tyre
inflatio
npressure
whencomparedto
LowPS
Iandoplusoplus(119875lt0001)com
paredto
Mod
PSI
8 Shock and Vibration
Table4MeanplusmnSD
form
ovem
entsseparatedforlow
(lt5H
z)andhigh
(gt5H
z)po
wer
Accelerometer
position
Cyclo
Xkingtyre
2210158401015840XK
ingtyreclubsclubs
2410158401015840XK
ingtyre
3-way
ANOVA
LowPS
IMod
PSI
HighPS
ILo
wPS
IMod
PSIoplusoplusoplusoplus
HighPS
ILo
wPS
IMod
PSI
HighPS
Iotimesotimesotimesotimes
Lowpo
wer
hand
lebar
76020plusmn0372
73377plusmn0730
73461plusmn
0722
79999plusmn0706
80373plusmn0601
78545plusmn066
777
180plusmn0535
81915plusmn0921
73545plusmn0496
Tyrelowastlowastlowast
ALoclowastlowastlowastlowast
TyrelowastALoclowast
PSIlowast
ALoclowast
Wris
t1110
12plusmn14
331110
16plusmn0798
108242plusmn0665112274plusmn0783
113173plusmn0791
111153plusmn0940
107093plusmn0831
112719plusmn1111
1117
09plusmn14
81Ank
le88034plusmn12
8687661plusmn15
7491
143plusmn15
0485389plusmn15
5685304plusmn13
6793
778plusmn12
2886588plusmn18
5177
914plusmn0866
89735plusmn15
55Seatpo
st70
221plusmn
0892
69096plusmn1130
69559plusmn1100
77862plusmn0844
7740
8plusmn0802
76287plusmn0682
74695plusmn0979
81789plusmn15
9575
053plusmn0870
Lumbar
22323plusmn0428
22711plusmn0431
22088plusmn0555
23851plusmn0393
23896plusmn0385
24398plusmn0512
21917plusmn0240
21500plusmn0199
22178plusmn0242
Forehead
16805plusmn0125
15723plusmn0205
16235plusmn0241
17659plusmn0225
17505plusmn0263
15788plusmn0168
17763plusmn046
016
319plusmn0482
16620plusmn0461
Highpo
wer
hand
lebar
309527plusmn10
84316942plusmn2200
319095plusmn1144
313476plusmn16
95325003plusmn2085328681plusmn
1642
309170plusmn2816
325744plusmn2808338956plusmn2025PS
Ilowastlowastlowastlowast
ALoclowastlowastlowastlowast
TyrelowastPS
Ilowastlowast
TyrelowastALoclowastlowast
PSIlowast
ALoclowast
Wris
t310326plusmn17
613118
62plusmn19
44319101plusmn
1745
308851plusmn
1646
307399plusmn15
88324736plusmn18
583110
31plusmn16
343252
17plusmn2201
320763plusmn10
01Ank
le320164plusmn2753
307261plusmn
1813
308363plusmn19
35294291plusmn
1562
297999plusmn19
623119
27plusmn1746
299579plusmn4112
287204plusmn1748
3252
10plusmn2184
Seatpo
st343183plusmn2782
339910plusmn2618
3374
90plusmn19
463114
56plusmn2294324106plusmn204
8339546plusmn19
09306605plusmn4610324129plusmn356434364
6plusmn2565
Lumbar
540
80plusmn12
6055831plusmn0971
544
96plusmn1139
53255plusmn13
3454598plusmn12
1254818plusmn12
1248842plusmn0432
46912plusmn0481
53320plusmn0485
Forehead
55814plusmn13
9762502plusmn0620
58694plusmn0998
49398plusmn10
8350786plusmn14
2353796plusmn1525
57876plusmn1741
46845plusmn0808
59633plusmn15
70Where
tyre
(tyre
size)P
SI(ty
reinflatio
npressure)andALoc
(accele
rometer
locatio
n)refertothem
aineffectfor
power
band
Tyrelowast
ALoc
refersto
thetwo-way
interactionbetweentyre
sizea
ndaccelerometer
locatio
nlowastdeno
tessignificance
(119875lt005)lowastlowast(119875lt001)lowastlowastlowast(119875lt0001)lowastlowastlowastlowast(119875lt00001)clubsclubssig
nifiesa
postho
cdifference
(119875lt001)for
lowpo
wer
whencomparedto
cyclo
XKingtyre
sizeotimesotimesotimesotimessig
nifiesa
postho
cdifference
(119875lt00001)for
tyre
inflatio
npressure
whencomparedto
LowPS
Iandoplusoplusoplusoplus(119875lt00001)com
paredto
HighPS
I
Shock and Vibration 9
In the first instance Figure 4 identifies the highly signifi-cant (119875 lt 00001) effect of tyre size on performance timewithregard to normalised tyre inflation pressures This is furtherexacerbated considering the typical tyre inflation pressure(moderate Figure 3) used by competitive XCO-MTB athletes[16] At this pressure post hoc analysis identified differencesbetween 2210158401015840 and 2410158401015840 XKing tyres suggesting that tyre sizecould have considerable effect on performance
While difficult to glean conclusive data regarding overallXCO-MTB performance from such a small downhill com-ponent of performance as collected in this study it is worthnoting that previous research has linked decreased vibrationexposure to increased efficiency [10 11] As such the attenu-ation of accelerations experienced (Figure 5 and Tables 3 and4) at the point of contact between human and bicycle (han-dlebar and seat post) as a result of increased tyre size couldtheoretically be connected to overall performance duringcomplete race distance This obviously assumes that the dec-rease in nonpropulsive work would reduce muscular andcognitive fatigue and consequentially increase performanceHowever it is acknowledged that a complete XCO-MTB raceentails a variety of surfaces and terrains where themajority oftime is spent cycling uphill on smoother surfaces that mightactually suit a smaller higher pressure tyre As such futureresearch is needed to explore this aspect
On the other hand tyre inflation pressure does not seemto influence performance in this experiment (Figure 4) eventhough an increase in accelerations in all axes (Figure 5)related to an increase in magnitude (Table 3) rather than fre-quency (Table 2) was apparent While interesting the tran-sient nature of the protocol used cannot corroborate thelong term effects that racing for ge90mins with the observedincreases in magnitude would have on accumulated muscu-lar fatigue Based on previous laboratorywork [6 19] it is beli-eved that XCO-MTB performance would be compromisedover a complete race distance but requires confirmation
Similar to previous work on the transference of acceler-ations during XCO-MTB [9] the data presented here showsthat both the bicycle and the soft tissue are dissipating energy[20 21] from the interaction of bicycle with surface terrainimplying a reduced nonpropulsive work component of XCO-MTB as a result of increased tyre size This is supportedthrough two-way interactions between both tyre size lowast accel-erometer position and tyre inflation pressure lowast accelero-meter location for total vertical and horizontal accelera-tions (Figure 5) magnitude (Table 3) and low-high powerdistribution (Table 4) As such the reduction in measuresassociated with acceleration exposure reported previouslydecreased at the point of interaction with the bicycle withan increase in tyre size Importantly this was accompaniedby reductions at the soft tissue sites implying a reduced non-propulsive work component of XCO-MTB as a result ofincreased tyre size Alternatively increases in tyre inflationpressure have the opposite and negative effect by increasingrider exposure to accelerations at the point of interface withbicycle and thus increase the non-propulsive componentAdditionally the controlled nature of this protocol mayenable participants to alter body position or riding style
dependent on tyre chracteristics not afforded during a racingsituation
5 Conclusion
This study set out to quantify the influence of tyre size andnormalised tyre inflation pressure on exposure to impactstypical to cross country mountain bike riding It was foundthat the larger the tyre size within the range tested thelower the level of impact exposure experienced at the pointof contact between bicycle and body This reduction meantparticipants performed less non-propulsive muscular workand performed better when compared to a smaller tyre of thesame construction and tread pattern Contrariwise highertyre inflation pressures were associated with an increase inthe level of impact exposure and thus greater soft tissue workin order to attenuate the larger impacts In addition it wasshown that increased tyre inflation pressure could interactnegatively with tyre size while increased tyre size couldinteract positively with tyre inflation pressure As such theeffects of reduced exposure need to be assessed with regardsto longer periods of time such as experienced in a mountainbike race or recreational ride
6 Practical Application
It is recommended that participants (recreational and com-petitive) use a higher volume tyre over any smaller alternativewithin the range tested here In doing so it is suggested thatparticipants could improve performance and likely reducethe risk of overuse injuries or increase the time spent ridingfor the same risk(s)
It is important to note that two-way interactions betweentyre size and tyre inflation pressures suggest that the benefitsof riding with a bigger tyre could be negated through the useof high tyre inflation pressure Conversely the use of lowertyre inflation pressures in smaller tyres could reduce exposurebut must come with a warning of increased unreliability interms of punctures and de-beading from the wheel rim
7 Future Research
The findings of this study must now be verified over a com-plete XCO-MTB race lap consisting of a variety of terrainsto enable whole performance analysis and terrain specificsection performance analysis
Conflict of Interests
The authors declare that there is no conflict of interestsregarding the publication of this paper
References
[1] H THurst and S Atkins ldquoPower output of field-based downhillmountain bikingrdquo Journal of Sports Sciences vol 24 no 10 pp1047ndash1053 2006
[2] F M Impellizzeri and S M Marcora ldquoThe physiology ofmountain bikingrdquo SportsMedicine vol 37 no 1 pp 59ndash71 2007
10 Shock and Vibration
[3] P W Macdermid and S Stannard ldquoMechanical work andphysiological responses to simulated cross country mountainbike racingrdquo Journal of Sports Sciences vol 30 no 14 pp 1491ndash1501 2012
[4] B Stapelfeldt A Schwirtz Y O Schumacher and M Hille-brecht ldquoWorkload demands in mountain bike racingrdquo Interna-tional Journal of Sports Medicine vol 25 no 4 pp 294ndash3002004
[5] P Macdermid P Fink and S Stannard ldquoThe effects of vibra-tions experienced during road vs off-road cyclingrdquo Interna-tional Journal of Sports Medicine 2015
[6] B Samuelson L Jorfeldt and B Ahlborg ldquoInfluence of vibra-tion on endurance of maximal isometric contractionrdquo ClinicalPhysiology vol 9 no 1 pp 21ndash25 1989
[7] J Titlestad A Fairlie-Clarke M Davie A Whittaker and SGrant ldquoExperimental evaluation of mountain bike suspensionsystemsrdquo Acta Polytechnica vol 43 no 5 2003
[8] H T Hurst M Swaren K Hebert-Losier et al ldquoInfluenceof course type on upper body muscle activity in elite Cross-Country andDownhillmountain bikers during offRoadDown-hill Cyclingrdquo Journal of Science and Cycling vol 1 no 2 pp 2ndash92012
[9] P W Macdermid P W Fink and S R Stannard ldquoTransferenceof 3D accelerations during cross country mountain bikingrdquoJournal of Biomechanics vol 47 no 8 pp 1829ndash1837 2014
[10] P W Macdermid P W Fink and S R Stannard ldquoThe effectsof vibrations experienced during road vs off-road cyclingrdquoInternational Journal of Sports Medicine 2015
[11] J Mester P Spitzenfeil J Schwarzer and F Seifriz ldquoBiologicalreaction to vibrationmdashimplications for sportrdquo Journal of Scienceand Medicine in Sport vol 2 no 3 pp 211ndash226 1999
[12] T Ishii Y Umerura and K Kitagawa ldquoInfluences of mountainbike suspension systems on energy supply and performancerdquoJapanese Journal of Biomechanics in Sports and Exercise vol 7pp 2ndash9 2003
[13] L M Sherwin P M O Owende C L Kanali J Lyons and SM Ward ldquoInfluence of tyre inflation pressure on whole-bodyvibrations transmitted to the operator in a cut-to-length timberharvesterrdquoApplied Ergonomics vol 35 no 3 pp 253ndash261 2004
[14] J Gordon J J Kauzlarich and J G Thacker ldquoTests of two newpolyurethane foam wheelchair tiresrdquo Journal of RehabilitationResearch and Development vol 26 no 1 pp 33ndash46 1989
[15] B J Sawatzky W O Kim and I Denison ldquoThe ergonomics ofdifferent tyres and tyre pressure during wheelchair propulsionrdquoErgonomics vol 47 no 14 pp 1475ndash1483 2004
[16] PWMacdermid PW Fink and S R Stannard ldquoThe influenceof tyre characteristics on measures of rolling performance dur-ing cross-country mountain bikingrdquo Journal of Sports Sciencesvol 33 no 3 pp 277ndash285 2015
[17] R Van der Plas Bicycle Technology Motorbooks International1991
[18] M Munera X Chiementin S Crequy and W Bertucci ldquoPhys-ical risk associated with vibration at cyclingrdquo Mechanics ampIndustry vol 15 no 6 pp 535ndash540 2014
[19] J Titlestad T Fairlie-Clarke A Whittaker M Davie I Wattand S Grant ldquoEffect of suspension systems on the physiologicaland psychological responses to sub-maximal biking on simu-lated smoothand bumpy tracksrdquo Journal of Sports Sciences vol24 no 2 pp 125ndash135 2006
[20] V B Issurin ldquoVibrations and their applications in sport areviewrdquo Journal of Sports Medicine and Physical Fitness vol 45no 3 pp 324ndash336 2005
[21] M Levy and G A Smith ldquoEffectiveness of vibration dampingwith bicycle suspension systemsrdquo Sports Engineering vol 8 no2 pp 99ndash106 2005
International Journal of
AerospaceEngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
RoboticsJournal of
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Active and Passive Electronic Components
Control Scienceand Engineering
Journal of
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International Journal of
RotatingMachinery
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporation httpwwwhindawicom
Journal ofEngineeringVolume 2014
Submit your manuscripts athttpwwwhindawicom
VLSI Design
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Shock and Vibration
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Civil EngineeringAdvances in
Acoustics and VibrationAdvances in
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Electrical and Computer Engineering
Journal of
Advances inOptoElectronics
Hindawi Publishing Corporation httpwwwhindawicom
Volume 2014
The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014
SensorsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Modelling amp Simulation in EngineeringHindawi Publishing Corporation httpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Chemical EngineeringInternational Journal of Antennas and
Propagation
International Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Navigation and Observation
International Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
DistributedSensor Networks
International Journal of
6 Shock and Vibration
Table2MeanplusmnSD
form
axim
umfre
quency
(Hz)of
acceleratio
nsdu
ringthetria
lseparatedfora
ccelerom
eter
locatio
ntyre
sizeandtyre
inflatio
npressure
Accelerometer
position
Cyclo
XKingtyreclubsclubsclubsclubs
2210158401015840XK
ingtyre
2410158401015840XK
ingtyre
3-way
ANOVA
LowPS
IMod
PSI
HighPS
ILo
wPS
IMod
PSI
HighPS
ILo
wPS
IMod
PSI
HighPS
IHandlebar
05284plusmn0049
05084plusmn004
605099plusmn006
005659plusmn0043
05632plusmn0036
05526plusmn0036
05781plusmn0029
060
03plusmn0055
05565plusmn0032
Tyrelowastlowastlowastlowast
PSIN
S
ALoclowastlowastlowastlowast
TyrelowastALoclowastlowastlowastlowast
Wris
t05284plusmn0049
05084plusmn004
605099plusmn006
005659plusmn0043
05632plusmn0037
05526plusmn0037
05781plusmn0029
060
03plusmn0055
05787plusmn0076
Ank
le05284plusmn0049
05084plusmn004
605099plusmn006
005659plusmn0043
05632plusmn0037
05526plusmn0036
05781plusmn0029
060
03plusmn0055
05787plusmn0032
Seatpo
st05284plusmn0049
05088plusmn0036
05099plusmn0036
05659plusmn0043
05654plusmn0036
05539plusmn0036
05781plusmn0029
060
03plusmn0055
05565plusmn0032
Lumbarotimesotimesotimesotimes
08372plusmn0760
08165plusmn0756
05345plusmn0123
13076plusmn1168
18315plusmn10
3416
682plusmn14
5320180plusmn14
2113
681plusmn
1034
14722plusmn1166
Forehead
05749plusmn0259
05088plusmn004
605099plusmn006
006518plusmn0284
05202plusmn0123
05098plusmn0121
05749plusmn0030
060
49plusmn0051
05117plusmn0117
Tyre(ty
resiz
e)PSI
(tyreinflatio
npressure)andALoc
(accelerom
eter
position)
refertothem
aineffectfor
maxim
umfre
quencyTyrelowast
ALoc
refersto
thetwo-way
interactionbetweentyresiz
eand
accelerometer
position
NSdeno
tesa
nonsignificanteffect(119875gt0005)lowastlowastlowastlowast(119875lt00001)clubsclubsclubsclubssig
nifiesa
postho
cdifference
(119875lt00001)for
tyre
sizew
hencomparin
gcyclo
XKingto
both
2210158401015840and2410158401015840XK
ingtyreotimesotimesotimesotimes
signifiesa
postho
cdifference
(119875lt00001)for
accelerometer
positionwhencomparedto
allother
accelerometer
positions
Shock and Vibration 7
Table3MeanplusmnSD
form
axim
ummagnitude
(g2 )of
acceleratio
nsdu
ringthetria
lseparatedfora
ccelerom
eter
locatio
ntyre
sizeandtyre
inflatio
npressure
Accelerometer
position
Cyclo
XKingtyre
2210158401015840XK
ingtyreclubsclubs
2410158401015840XK
ingtyreclubsclubsclubsclubs
3-way
ANOVA
LowPS
IMod
PSIoplus
HighPS
Ioplusoplus
LowPS
IMod
PSIoplus
HighPS
Ioplusoplus
LowPS
IMod
PSIoplus
HighPS
Ioplusoplus
Handlebar
96649plusmn0483
98169plusmn0837
99169plusmn0394
91121plusmn
0572
95915plusmn040
799
974plusmn0523
860
00plusmn076591403plusmn0489
96618plusmn0356
Tyrelowastlowastlowastlowast
PSIlowastlowastlowastlowast
ALoclowastlowastlowastlowast
TyrelowastALoclowastlowastlowastlowast
PSIlowast
ALoclowastlowastlowastlowast
Wris
t89805plusmn0969
92501plusmn
1016
93962plusmn0698
84191plusmn0744
86780plusmn0770
91158plusmn0944
80720plusmn0897
88992plusmn10
9285109plusmn0374
Ank
le104872plusmn0882106966plusmn12
44108250plusmn0903
90277plusmn13
9991
134plusmn0990
1015
14plusmn0970
86496plusmn14
3174
320plusmn0793
95862plusmn1127
Seatpo
st85581plusmn0596
88560plusmn10
0988657plusmn0831
85843plusmn10
9791
929plusmn0997
95898plusmn0936
81989plusmn14
0789681plusmn13
7592
576plusmn0977
Lumbar
09245plusmn0201
10165plusmn0315
09747plusmn0279
09550plusmn0198
09176plusmn0129
09810plusmn0169
08461plusmn0094
09134plusmn0124
09347plusmn0138
Forehead
12333plusmn0265
11829plusmn0106
12301plusmn
0220
10693plusmn
0184
11935plusmn0218
11763plusmn0147
11001plusmn
0150
10876plusmn0210
11283plusmn0244
Tyre(ty
resiz
e)PSI
(tyreinflatio
npressure)andALoc
(accelerom
eter
position)
refertothem
aineffectfor
maxim
umfre
quencyTyrelowast
ALoc
refersto
thetwo-way
interactionbetweentyresiz
eand
accelerometer
position
NSdeno
tesa
nonsignificanteffect(119875gt0005)lowastlowastlowastlowast(119875lt00001)clubsclubsclubsclubssig
nifiesa
postho
cdifference
(119875lt00001)a
ndclubsclubs(119875lt001)for
tyre
sizew
hencomparedto
cyclo
XKingtyreotimesotimesotimesotimessig
nifiesa
postho
cdifference
(119875lt00001)otimesandoplus(119875lt005)for
tyre
inflatio
npressure
whencomparedto
LowPS
Iandoplusoplus(119875lt0001)com
paredto
Mod
PSI
8 Shock and Vibration
Table4MeanplusmnSD
form
ovem
entsseparatedforlow
(lt5H
z)andhigh
(gt5H
z)po
wer
Accelerometer
position
Cyclo
Xkingtyre
2210158401015840XK
ingtyreclubsclubs
2410158401015840XK
ingtyre
3-way
ANOVA
LowPS
IMod
PSI
HighPS
ILo
wPS
IMod
PSIoplusoplusoplusoplus
HighPS
ILo
wPS
IMod
PSI
HighPS
Iotimesotimesotimesotimes
Lowpo
wer
hand
lebar
76020plusmn0372
73377plusmn0730
73461plusmn
0722
79999plusmn0706
80373plusmn0601
78545plusmn066
777
180plusmn0535
81915plusmn0921
73545plusmn0496
Tyrelowastlowastlowast
ALoclowastlowastlowastlowast
TyrelowastALoclowast
PSIlowast
ALoclowast
Wris
t1110
12plusmn14
331110
16plusmn0798
108242plusmn0665112274plusmn0783
113173plusmn0791
111153plusmn0940
107093plusmn0831
112719plusmn1111
1117
09plusmn14
81Ank
le88034plusmn12
8687661plusmn15
7491
143plusmn15
0485389plusmn15
5685304plusmn13
6793
778plusmn12
2886588plusmn18
5177
914plusmn0866
89735plusmn15
55Seatpo
st70
221plusmn
0892
69096plusmn1130
69559plusmn1100
77862plusmn0844
7740
8plusmn0802
76287plusmn0682
74695plusmn0979
81789plusmn15
9575
053plusmn0870
Lumbar
22323plusmn0428
22711plusmn0431
22088plusmn0555
23851plusmn0393
23896plusmn0385
24398plusmn0512
21917plusmn0240
21500plusmn0199
22178plusmn0242
Forehead
16805plusmn0125
15723plusmn0205
16235plusmn0241
17659plusmn0225
17505plusmn0263
15788plusmn0168
17763plusmn046
016
319plusmn0482
16620plusmn0461
Highpo
wer
hand
lebar
309527plusmn10
84316942plusmn2200
319095plusmn1144
313476plusmn16
95325003plusmn2085328681plusmn
1642
309170plusmn2816
325744plusmn2808338956plusmn2025PS
Ilowastlowastlowastlowast
ALoclowastlowastlowastlowast
TyrelowastPS
Ilowastlowast
TyrelowastALoclowastlowast
PSIlowast
ALoclowast
Wris
t310326plusmn17
613118
62plusmn19
44319101plusmn
1745
308851plusmn
1646
307399plusmn15
88324736plusmn18
583110
31plusmn16
343252
17plusmn2201
320763plusmn10
01Ank
le320164plusmn2753
307261plusmn
1813
308363plusmn19
35294291plusmn
1562
297999plusmn19
623119
27plusmn1746
299579plusmn4112
287204plusmn1748
3252
10plusmn2184
Seatpo
st343183plusmn2782
339910plusmn2618
3374
90plusmn19
463114
56plusmn2294324106plusmn204
8339546plusmn19
09306605plusmn4610324129plusmn356434364
6plusmn2565
Lumbar
540
80plusmn12
6055831plusmn0971
544
96plusmn1139
53255plusmn13
3454598plusmn12
1254818plusmn12
1248842plusmn0432
46912plusmn0481
53320plusmn0485
Forehead
55814plusmn13
9762502plusmn0620
58694plusmn0998
49398plusmn10
8350786plusmn14
2353796plusmn1525
57876plusmn1741
46845plusmn0808
59633plusmn15
70Where
tyre
(tyre
size)P
SI(ty
reinflatio
npressure)andALoc
(accele
rometer
locatio
n)refertothem
aineffectfor
power
band
Tyrelowast
ALoc
refersto
thetwo-way
interactionbetweentyre
sizea
ndaccelerometer
locatio
nlowastdeno
tessignificance
(119875lt005)lowastlowast(119875lt001)lowastlowastlowast(119875lt0001)lowastlowastlowastlowast(119875lt00001)clubsclubssig
nifiesa
postho
cdifference
(119875lt001)for
lowpo
wer
whencomparedto
cyclo
XKingtyre
sizeotimesotimesotimesotimessig
nifiesa
postho
cdifference
(119875lt00001)for
tyre
inflatio
npressure
whencomparedto
LowPS
Iandoplusoplusoplusoplus(119875lt00001)com
paredto
HighPS
I
Shock and Vibration 9
In the first instance Figure 4 identifies the highly signifi-cant (119875 lt 00001) effect of tyre size on performance timewithregard to normalised tyre inflation pressures This is furtherexacerbated considering the typical tyre inflation pressure(moderate Figure 3) used by competitive XCO-MTB athletes[16] At this pressure post hoc analysis identified differencesbetween 2210158401015840 and 2410158401015840 XKing tyres suggesting that tyre sizecould have considerable effect on performance
While difficult to glean conclusive data regarding overallXCO-MTB performance from such a small downhill com-ponent of performance as collected in this study it is worthnoting that previous research has linked decreased vibrationexposure to increased efficiency [10 11] As such the attenu-ation of accelerations experienced (Figure 5 and Tables 3 and4) at the point of contact between human and bicycle (han-dlebar and seat post) as a result of increased tyre size couldtheoretically be connected to overall performance duringcomplete race distance This obviously assumes that the dec-rease in nonpropulsive work would reduce muscular andcognitive fatigue and consequentially increase performanceHowever it is acknowledged that a complete XCO-MTB raceentails a variety of surfaces and terrains where themajority oftime is spent cycling uphill on smoother surfaces that mightactually suit a smaller higher pressure tyre As such futureresearch is needed to explore this aspect
On the other hand tyre inflation pressure does not seemto influence performance in this experiment (Figure 4) eventhough an increase in accelerations in all axes (Figure 5)related to an increase in magnitude (Table 3) rather than fre-quency (Table 2) was apparent While interesting the tran-sient nature of the protocol used cannot corroborate thelong term effects that racing for ge90mins with the observedincreases in magnitude would have on accumulated muscu-lar fatigue Based on previous laboratorywork [6 19] it is beli-eved that XCO-MTB performance would be compromisedover a complete race distance but requires confirmation
Similar to previous work on the transference of acceler-ations during XCO-MTB [9] the data presented here showsthat both the bicycle and the soft tissue are dissipating energy[20 21] from the interaction of bicycle with surface terrainimplying a reduced nonpropulsive work component of XCO-MTB as a result of increased tyre size This is supportedthrough two-way interactions between both tyre size lowast accel-erometer position and tyre inflation pressure lowast accelero-meter location for total vertical and horizontal accelera-tions (Figure 5) magnitude (Table 3) and low-high powerdistribution (Table 4) As such the reduction in measuresassociated with acceleration exposure reported previouslydecreased at the point of interaction with the bicycle withan increase in tyre size Importantly this was accompaniedby reductions at the soft tissue sites implying a reduced non-propulsive work component of XCO-MTB as a result ofincreased tyre size Alternatively increases in tyre inflationpressure have the opposite and negative effect by increasingrider exposure to accelerations at the point of interface withbicycle and thus increase the non-propulsive componentAdditionally the controlled nature of this protocol mayenable participants to alter body position or riding style
dependent on tyre chracteristics not afforded during a racingsituation
5 Conclusion
This study set out to quantify the influence of tyre size andnormalised tyre inflation pressure on exposure to impactstypical to cross country mountain bike riding It was foundthat the larger the tyre size within the range tested thelower the level of impact exposure experienced at the pointof contact between bicycle and body This reduction meantparticipants performed less non-propulsive muscular workand performed better when compared to a smaller tyre of thesame construction and tread pattern Contrariwise highertyre inflation pressures were associated with an increase inthe level of impact exposure and thus greater soft tissue workin order to attenuate the larger impacts In addition it wasshown that increased tyre inflation pressure could interactnegatively with tyre size while increased tyre size couldinteract positively with tyre inflation pressure As such theeffects of reduced exposure need to be assessed with regardsto longer periods of time such as experienced in a mountainbike race or recreational ride
6 Practical Application
It is recommended that participants (recreational and com-petitive) use a higher volume tyre over any smaller alternativewithin the range tested here In doing so it is suggested thatparticipants could improve performance and likely reducethe risk of overuse injuries or increase the time spent ridingfor the same risk(s)
It is important to note that two-way interactions betweentyre size and tyre inflation pressures suggest that the benefitsof riding with a bigger tyre could be negated through the useof high tyre inflation pressure Conversely the use of lowertyre inflation pressures in smaller tyres could reduce exposurebut must come with a warning of increased unreliability interms of punctures and de-beading from the wheel rim
7 Future Research
The findings of this study must now be verified over a com-plete XCO-MTB race lap consisting of a variety of terrainsto enable whole performance analysis and terrain specificsection performance analysis
Conflict of Interests
The authors declare that there is no conflict of interestsregarding the publication of this paper
References
[1] H THurst and S Atkins ldquoPower output of field-based downhillmountain bikingrdquo Journal of Sports Sciences vol 24 no 10 pp1047ndash1053 2006
[2] F M Impellizzeri and S M Marcora ldquoThe physiology ofmountain bikingrdquo SportsMedicine vol 37 no 1 pp 59ndash71 2007
10 Shock and Vibration
[3] P W Macdermid and S Stannard ldquoMechanical work andphysiological responses to simulated cross country mountainbike racingrdquo Journal of Sports Sciences vol 30 no 14 pp 1491ndash1501 2012
[4] B Stapelfeldt A Schwirtz Y O Schumacher and M Hille-brecht ldquoWorkload demands in mountain bike racingrdquo Interna-tional Journal of Sports Medicine vol 25 no 4 pp 294ndash3002004
[5] P Macdermid P Fink and S Stannard ldquoThe effects of vibra-tions experienced during road vs off-road cyclingrdquo Interna-tional Journal of Sports Medicine 2015
[6] B Samuelson L Jorfeldt and B Ahlborg ldquoInfluence of vibra-tion on endurance of maximal isometric contractionrdquo ClinicalPhysiology vol 9 no 1 pp 21ndash25 1989
[7] J Titlestad A Fairlie-Clarke M Davie A Whittaker and SGrant ldquoExperimental evaluation of mountain bike suspensionsystemsrdquo Acta Polytechnica vol 43 no 5 2003
[8] H T Hurst M Swaren K Hebert-Losier et al ldquoInfluenceof course type on upper body muscle activity in elite Cross-Country andDownhillmountain bikers during offRoadDown-hill Cyclingrdquo Journal of Science and Cycling vol 1 no 2 pp 2ndash92012
[9] P W Macdermid P W Fink and S R Stannard ldquoTransferenceof 3D accelerations during cross country mountain bikingrdquoJournal of Biomechanics vol 47 no 8 pp 1829ndash1837 2014
[10] P W Macdermid P W Fink and S R Stannard ldquoThe effectsof vibrations experienced during road vs off-road cyclingrdquoInternational Journal of Sports Medicine 2015
[11] J Mester P Spitzenfeil J Schwarzer and F Seifriz ldquoBiologicalreaction to vibrationmdashimplications for sportrdquo Journal of Scienceand Medicine in Sport vol 2 no 3 pp 211ndash226 1999
[12] T Ishii Y Umerura and K Kitagawa ldquoInfluences of mountainbike suspension systems on energy supply and performancerdquoJapanese Journal of Biomechanics in Sports and Exercise vol 7pp 2ndash9 2003
[13] L M Sherwin P M O Owende C L Kanali J Lyons and SM Ward ldquoInfluence of tyre inflation pressure on whole-bodyvibrations transmitted to the operator in a cut-to-length timberharvesterrdquoApplied Ergonomics vol 35 no 3 pp 253ndash261 2004
[14] J Gordon J J Kauzlarich and J G Thacker ldquoTests of two newpolyurethane foam wheelchair tiresrdquo Journal of RehabilitationResearch and Development vol 26 no 1 pp 33ndash46 1989
[15] B J Sawatzky W O Kim and I Denison ldquoThe ergonomics ofdifferent tyres and tyre pressure during wheelchair propulsionrdquoErgonomics vol 47 no 14 pp 1475ndash1483 2004
[16] PWMacdermid PW Fink and S R Stannard ldquoThe influenceof tyre characteristics on measures of rolling performance dur-ing cross-country mountain bikingrdquo Journal of Sports Sciencesvol 33 no 3 pp 277ndash285 2015
[17] R Van der Plas Bicycle Technology Motorbooks International1991
[18] M Munera X Chiementin S Crequy and W Bertucci ldquoPhys-ical risk associated with vibration at cyclingrdquo Mechanics ampIndustry vol 15 no 6 pp 535ndash540 2014
[19] J Titlestad T Fairlie-Clarke A Whittaker M Davie I Wattand S Grant ldquoEffect of suspension systems on the physiologicaland psychological responses to sub-maximal biking on simu-lated smoothand bumpy tracksrdquo Journal of Sports Sciences vol24 no 2 pp 125ndash135 2006
[20] V B Issurin ldquoVibrations and their applications in sport areviewrdquo Journal of Sports Medicine and Physical Fitness vol 45no 3 pp 324ndash336 2005
[21] M Levy and G A Smith ldquoEffectiveness of vibration dampingwith bicycle suspension systemsrdquo Sports Engineering vol 8 no2 pp 99ndash106 2005
International Journal of
AerospaceEngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
RoboticsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Active and Passive Electronic Components
Control Scienceand Engineering
Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
International Journal of
RotatingMachinery
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporation httpwwwhindawicom
Journal ofEngineeringVolume 2014
Submit your manuscripts athttpwwwhindawicom
VLSI Design
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Shock and Vibration
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Civil EngineeringAdvances in
Acoustics and VibrationAdvances in
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Electrical and Computer Engineering
Journal of
Advances inOptoElectronics
Hindawi Publishing Corporation httpwwwhindawicom
Volume 2014
The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014
SensorsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Modelling amp Simulation in EngineeringHindawi Publishing Corporation httpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Chemical EngineeringInternational Journal of Antennas and
Propagation
International Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Navigation and Observation
International Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
DistributedSensor Networks
International Journal of
Shock and Vibration 7
Table3MeanplusmnSD
form
axim
ummagnitude
(g2 )of
acceleratio
nsdu
ringthetria
lseparatedfora
ccelerom
eter
locatio
ntyre
sizeandtyre
inflatio
npressure
Accelerometer
position
Cyclo
XKingtyre
2210158401015840XK
ingtyreclubsclubs
2410158401015840XK
ingtyreclubsclubsclubsclubs
3-way
ANOVA
LowPS
IMod
PSIoplus
HighPS
Ioplusoplus
LowPS
IMod
PSIoplus
HighPS
Ioplusoplus
LowPS
IMod
PSIoplus
HighPS
Ioplusoplus
Handlebar
96649plusmn0483
98169plusmn0837
99169plusmn0394
91121plusmn
0572
95915plusmn040
799
974plusmn0523
860
00plusmn076591403plusmn0489
96618plusmn0356
Tyrelowastlowastlowastlowast
PSIlowastlowastlowastlowast
ALoclowastlowastlowastlowast
TyrelowastALoclowastlowastlowastlowast
PSIlowast
ALoclowastlowastlowastlowast
Wris
t89805plusmn0969
92501plusmn
1016
93962plusmn0698
84191plusmn0744
86780plusmn0770
91158plusmn0944
80720plusmn0897
88992plusmn10
9285109plusmn0374
Ank
le104872plusmn0882106966plusmn12
44108250plusmn0903
90277plusmn13
9991
134plusmn0990
1015
14plusmn0970
86496plusmn14
3174
320plusmn0793
95862plusmn1127
Seatpo
st85581plusmn0596
88560plusmn10
0988657plusmn0831
85843plusmn10
9791
929plusmn0997
95898plusmn0936
81989plusmn14
0789681plusmn13
7592
576plusmn0977
Lumbar
09245plusmn0201
10165plusmn0315
09747plusmn0279
09550plusmn0198
09176plusmn0129
09810plusmn0169
08461plusmn0094
09134plusmn0124
09347plusmn0138
Forehead
12333plusmn0265
11829plusmn0106
12301plusmn
0220
10693plusmn
0184
11935plusmn0218
11763plusmn0147
11001plusmn
0150
10876plusmn0210
11283plusmn0244
Tyre(ty
resiz
e)PSI
(tyreinflatio
npressure)andALoc
(accelerom
eter
position)
refertothem
aineffectfor
maxim
umfre
quencyTyrelowast
ALoc
refersto
thetwo-way
interactionbetweentyresiz
eand
accelerometer
position
NSdeno
tesa
nonsignificanteffect(119875gt0005)lowastlowastlowastlowast(119875lt00001)clubsclubsclubsclubssig
nifiesa
postho
cdifference
(119875lt00001)a
ndclubsclubs(119875lt001)for
tyre
sizew
hencomparedto
cyclo
XKingtyreotimesotimesotimesotimessig
nifiesa
postho
cdifference
(119875lt00001)otimesandoplus(119875lt005)for
tyre
inflatio
npressure
whencomparedto
LowPS
Iandoplusoplus(119875lt0001)com
paredto
Mod
PSI
8 Shock and Vibration
Table4MeanplusmnSD
form
ovem
entsseparatedforlow
(lt5H
z)andhigh
(gt5H
z)po
wer
Accelerometer
position
Cyclo
Xkingtyre
2210158401015840XK
ingtyreclubsclubs
2410158401015840XK
ingtyre
3-way
ANOVA
LowPS
IMod
PSI
HighPS
ILo
wPS
IMod
PSIoplusoplusoplusoplus
HighPS
ILo
wPS
IMod
PSI
HighPS
Iotimesotimesotimesotimes
Lowpo
wer
hand
lebar
76020plusmn0372
73377plusmn0730
73461plusmn
0722
79999plusmn0706
80373plusmn0601
78545plusmn066
777
180plusmn0535
81915plusmn0921
73545plusmn0496
Tyrelowastlowastlowast
ALoclowastlowastlowastlowast
TyrelowastALoclowast
PSIlowast
ALoclowast
Wris
t1110
12plusmn14
331110
16plusmn0798
108242plusmn0665112274plusmn0783
113173plusmn0791
111153plusmn0940
107093plusmn0831
112719plusmn1111
1117
09plusmn14
81Ank
le88034plusmn12
8687661plusmn15
7491
143plusmn15
0485389plusmn15
5685304plusmn13
6793
778plusmn12
2886588plusmn18
5177
914plusmn0866
89735plusmn15
55Seatpo
st70
221plusmn
0892
69096plusmn1130
69559plusmn1100
77862plusmn0844
7740
8plusmn0802
76287plusmn0682
74695plusmn0979
81789plusmn15
9575
053plusmn0870
Lumbar
22323plusmn0428
22711plusmn0431
22088plusmn0555
23851plusmn0393
23896plusmn0385
24398plusmn0512
21917plusmn0240
21500plusmn0199
22178plusmn0242
Forehead
16805plusmn0125
15723plusmn0205
16235plusmn0241
17659plusmn0225
17505plusmn0263
15788plusmn0168
17763plusmn046
016
319plusmn0482
16620plusmn0461
Highpo
wer
hand
lebar
309527plusmn10
84316942plusmn2200
319095plusmn1144
313476plusmn16
95325003plusmn2085328681plusmn
1642
309170plusmn2816
325744plusmn2808338956plusmn2025PS
Ilowastlowastlowastlowast
ALoclowastlowastlowastlowast
TyrelowastPS
Ilowastlowast
TyrelowastALoclowastlowast
PSIlowast
ALoclowast
Wris
t310326plusmn17
613118
62plusmn19
44319101plusmn
1745
308851plusmn
1646
307399plusmn15
88324736plusmn18
583110
31plusmn16
343252
17plusmn2201
320763plusmn10
01Ank
le320164plusmn2753
307261plusmn
1813
308363plusmn19
35294291plusmn
1562
297999plusmn19
623119
27plusmn1746
299579plusmn4112
287204plusmn1748
3252
10plusmn2184
Seatpo
st343183plusmn2782
339910plusmn2618
3374
90plusmn19
463114
56plusmn2294324106plusmn204
8339546plusmn19
09306605plusmn4610324129plusmn356434364
6plusmn2565
Lumbar
540
80plusmn12
6055831plusmn0971
544
96plusmn1139
53255plusmn13
3454598plusmn12
1254818plusmn12
1248842plusmn0432
46912plusmn0481
53320plusmn0485
Forehead
55814plusmn13
9762502plusmn0620
58694plusmn0998
49398plusmn10
8350786plusmn14
2353796plusmn1525
57876plusmn1741
46845plusmn0808
59633plusmn15
70Where
tyre
(tyre
size)P
SI(ty
reinflatio
npressure)andALoc
(accele
rometer
locatio
n)refertothem
aineffectfor
power
band
Tyrelowast
ALoc
refersto
thetwo-way
interactionbetweentyre
sizea
ndaccelerometer
locatio
nlowastdeno
tessignificance
(119875lt005)lowastlowast(119875lt001)lowastlowastlowast(119875lt0001)lowastlowastlowastlowast(119875lt00001)clubsclubssig
nifiesa
postho
cdifference
(119875lt001)for
lowpo
wer
whencomparedto
cyclo
XKingtyre
sizeotimesotimesotimesotimessig
nifiesa
postho
cdifference
(119875lt00001)for
tyre
inflatio
npressure
whencomparedto
LowPS
Iandoplusoplusoplusoplus(119875lt00001)com
paredto
HighPS
I
Shock and Vibration 9
In the first instance Figure 4 identifies the highly signifi-cant (119875 lt 00001) effect of tyre size on performance timewithregard to normalised tyre inflation pressures This is furtherexacerbated considering the typical tyre inflation pressure(moderate Figure 3) used by competitive XCO-MTB athletes[16] At this pressure post hoc analysis identified differencesbetween 2210158401015840 and 2410158401015840 XKing tyres suggesting that tyre sizecould have considerable effect on performance
While difficult to glean conclusive data regarding overallXCO-MTB performance from such a small downhill com-ponent of performance as collected in this study it is worthnoting that previous research has linked decreased vibrationexposure to increased efficiency [10 11] As such the attenu-ation of accelerations experienced (Figure 5 and Tables 3 and4) at the point of contact between human and bicycle (han-dlebar and seat post) as a result of increased tyre size couldtheoretically be connected to overall performance duringcomplete race distance This obviously assumes that the dec-rease in nonpropulsive work would reduce muscular andcognitive fatigue and consequentially increase performanceHowever it is acknowledged that a complete XCO-MTB raceentails a variety of surfaces and terrains where themajority oftime is spent cycling uphill on smoother surfaces that mightactually suit a smaller higher pressure tyre As such futureresearch is needed to explore this aspect
On the other hand tyre inflation pressure does not seemto influence performance in this experiment (Figure 4) eventhough an increase in accelerations in all axes (Figure 5)related to an increase in magnitude (Table 3) rather than fre-quency (Table 2) was apparent While interesting the tran-sient nature of the protocol used cannot corroborate thelong term effects that racing for ge90mins with the observedincreases in magnitude would have on accumulated muscu-lar fatigue Based on previous laboratorywork [6 19] it is beli-eved that XCO-MTB performance would be compromisedover a complete race distance but requires confirmation
Similar to previous work on the transference of acceler-ations during XCO-MTB [9] the data presented here showsthat both the bicycle and the soft tissue are dissipating energy[20 21] from the interaction of bicycle with surface terrainimplying a reduced nonpropulsive work component of XCO-MTB as a result of increased tyre size This is supportedthrough two-way interactions between both tyre size lowast accel-erometer position and tyre inflation pressure lowast accelero-meter location for total vertical and horizontal accelera-tions (Figure 5) magnitude (Table 3) and low-high powerdistribution (Table 4) As such the reduction in measuresassociated with acceleration exposure reported previouslydecreased at the point of interaction with the bicycle withan increase in tyre size Importantly this was accompaniedby reductions at the soft tissue sites implying a reduced non-propulsive work component of XCO-MTB as a result ofincreased tyre size Alternatively increases in tyre inflationpressure have the opposite and negative effect by increasingrider exposure to accelerations at the point of interface withbicycle and thus increase the non-propulsive componentAdditionally the controlled nature of this protocol mayenable participants to alter body position or riding style
dependent on tyre chracteristics not afforded during a racingsituation
5 Conclusion
This study set out to quantify the influence of tyre size andnormalised tyre inflation pressure on exposure to impactstypical to cross country mountain bike riding It was foundthat the larger the tyre size within the range tested thelower the level of impact exposure experienced at the pointof contact between bicycle and body This reduction meantparticipants performed less non-propulsive muscular workand performed better when compared to a smaller tyre of thesame construction and tread pattern Contrariwise highertyre inflation pressures were associated with an increase inthe level of impact exposure and thus greater soft tissue workin order to attenuate the larger impacts In addition it wasshown that increased tyre inflation pressure could interactnegatively with tyre size while increased tyre size couldinteract positively with tyre inflation pressure As such theeffects of reduced exposure need to be assessed with regardsto longer periods of time such as experienced in a mountainbike race or recreational ride
6 Practical Application
It is recommended that participants (recreational and com-petitive) use a higher volume tyre over any smaller alternativewithin the range tested here In doing so it is suggested thatparticipants could improve performance and likely reducethe risk of overuse injuries or increase the time spent ridingfor the same risk(s)
It is important to note that two-way interactions betweentyre size and tyre inflation pressures suggest that the benefitsof riding with a bigger tyre could be negated through the useof high tyre inflation pressure Conversely the use of lowertyre inflation pressures in smaller tyres could reduce exposurebut must come with a warning of increased unreliability interms of punctures and de-beading from the wheel rim
7 Future Research
The findings of this study must now be verified over a com-plete XCO-MTB race lap consisting of a variety of terrainsto enable whole performance analysis and terrain specificsection performance analysis
Conflict of Interests
The authors declare that there is no conflict of interestsregarding the publication of this paper
References
[1] H THurst and S Atkins ldquoPower output of field-based downhillmountain bikingrdquo Journal of Sports Sciences vol 24 no 10 pp1047ndash1053 2006
[2] F M Impellizzeri and S M Marcora ldquoThe physiology ofmountain bikingrdquo SportsMedicine vol 37 no 1 pp 59ndash71 2007
10 Shock and Vibration
[3] P W Macdermid and S Stannard ldquoMechanical work andphysiological responses to simulated cross country mountainbike racingrdquo Journal of Sports Sciences vol 30 no 14 pp 1491ndash1501 2012
[4] B Stapelfeldt A Schwirtz Y O Schumacher and M Hille-brecht ldquoWorkload demands in mountain bike racingrdquo Interna-tional Journal of Sports Medicine vol 25 no 4 pp 294ndash3002004
[5] P Macdermid P Fink and S Stannard ldquoThe effects of vibra-tions experienced during road vs off-road cyclingrdquo Interna-tional Journal of Sports Medicine 2015
[6] B Samuelson L Jorfeldt and B Ahlborg ldquoInfluence of vibra-tion on endurance of maximal isometric contractionrdquo ClinicalPhysiology vol 9 no 1 pp 21ndash25 1989
[7] J Titlestad A Fairlie-Clarke M Davie A Whittaker and SGrant ldquoExperimental evaluation of mountain bike suspensionsystemsrdquo Acta Polytechnica vol 43 no 5 2003
[8] H T Hurst M Swaren K Hebert-Losier et al ldquoInfluenceof course type on upper body muscle activity in elite Cross-Country andDownhillmountain bikers during offRoadDown-hill Cyclingrdquo Journal of Science and Cycling vol 1 no 2 pp 2ndash92012
[9] P W Macdermid P W Fink and S R Stannard ldquoTransferenceof 3D accelerations during cross country mountain bikingrdquoJournal of Biomechanics vol 47 no 8 pp 1829ndash1837 2014
[10] P W Macdermid P W Fink and S R Stannard ldquoThe effectsof vibrations experienced during road vs off-road cyclingrdquoInternational Journal of Sports Medicine 2015
[11] J Mester P Spitzenfeil J Schwarzer and F Seifriz ldquoBiologicalreaction to vibrationmdashimplications for sportrdquo Journal of Scienceand Medicine in Sport vol 2 no 3 pp 211ndash226 1999
[12] T Ishii Y Umerura and K Kitagawa ldquoInfluences of mountainbike suspension systems on energy supply and performancerdquoJapanese Journal of Biomechanics in Sports and Exercise vol 7pp 2ndash9 2003
[13] L M Sherwin P M O Owende C L Kanali J Lyons and SM Ward ldquoInfluence of tyre inflation pressure on whole-bodyvibrations transmitted to the operator in a cut-to-length timberharvesterrdquoApplied Ergonomics vol 35 no 3 pp 253ndash261 2004
[14] J Gordon J J Kauzlarich and J G Thacker ldquoTests of two newpolyurethane foam wheelchair tiresrdquo Journal of RehabilitationResearch and Development vol 26 no 1 pp 33ndash46 1989
[15] B J Sawatzky W O Kim and I Denison ldquoThe ergonomics ofdifferent tyres and tyre pressure during wheelchair propulsionrdquoErgonomics vol 47 no 14 pp 1475ndash1483 2004
[16] PWMacdermid PW Fink and S R Stannard ldquoThe influenceof tyre characteristics on measures of rolling performance dur-ing cross-country mountain bikingrdquo Journal of Sports Sciencesvol 33 no 3 pp 277ndash285 2015
[17] R Van der Plas Bicycle Technology Motorbooks International1991
[18] M Munera X Chiementin S Crequy and W Bertucci ldquoPhys-ical risk associated with vibration at cyclingrdquo Mechanics ampIndustry vol 15 no 6 pp 535ndash540 2014
[19] J Titlestad T Fairlie-Clarke A Whittaker M Davie I Wattand S Grant ldquoEffect of suspension systems on the physiologicaland psychological responses to sub-maximal biking on simu-lated smoothand bumpy tracksrdquo Journal of Sports Sciences vol24 no 2 pp 125ndash135 2006
[20] V B Issurin ldquoVibrations and their applications in sport areviewrdquo Journal of Sports Medicine and Physical Fitness vol 45no 3 pp 324ndash336 2005
[21] M Levy and G A Smith ldquoEffectiveness of vibration dampingwith bicycle suspension systemsrdquo Sports Engineering vol 8 no2 pp 99ndash106 2005
International Journal of
AerospaceEngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
RoboticsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Active and Passive Electronic Components
Control Scienceand Engineering
Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
International Journal of
RotatingMachinery
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporation httpwwwhindawicom
Journal ofEngineeringVolume 2014
Submit your manuscripts athttpwwwhindawicom
VLSI Design
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Shock and Vibration
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Civil EngineeringAdvances in
Acoustics and VibrationAdvances in
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Electrical and Computer Engineering
Journal of
Advances inOptoElectronics
Hindawi Publishing Corporation httpwwwhindawicom
Volume 2014
The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014
SensorsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Modelling amp Simulation in EngineeringHindawi Publishing Corporation httpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Chemical EngineeringInternational Journal of Antennas and
Propagation
International Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Navigation and Observation
International Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
DistributedSensor Networks
International Journal of
8 Shock and Vibration
Table4MeanplusmnSD
form
ovem
entsseparatedforlow
(lt5H
z)andhigh
(gt5H
z)po
wer
Accelerometer
position
Cyclo
Xkingtyre
2210158401015840XK
ingtyreclubsclubs
2410158401015840XK
ingtyre
3-way
ANOVA
LowPS
IMod
PSI
HighPS
ILo
wPS
IMod
PSIoplusoplusoplusoplus
HighPS
ILo
wPS
IMod
PSI
HighPS
Iotimesotimesotimesotimes
Lowpo
wer
hand
lebar
76020plusmn0372
73377plusmn0730
73461plusmn
0722
79999plusmn0706
80373plusmn0601
78545plusmn066
777
180plusmn0535
81915plusmn0921
73545plusmn0496
Tyrelowastlowastlowast
ALoclowastlowastlowastlowast
TyrelowastALoclowast
PSIlowast
ALoclowast
Wris
t1110
12plusmn14
331110
16plusmn0798
108242plusmn0665112274plusmn0783
113173plusmn0791
111153plusmn0940
107093plusmn0831
112719plusmn1111
1117
09plusmn14
81Ank
le88034plusmn12
8687661plusmn15
7491
143plusmn15
0485389plusmn15
5685304plusmn13
6793
778plusmn12
2886588plusmn18
5177
914plusmn0866
89735plusmn15
55Seatpo
st70
221plusmn
0892
69096plusmn1130
69559plusmn1100
77862plusmn0844
7740
8plusmn0802
76287plusmn0682
74695plusmn0979
81789plusmn15
9575
053plusmn0870
Lumbar
22323plusmn0428
22711plusmn0431
22088plusmn0555
23851plusmn0393
23896plusmn0385
24398plusmn0512
21917plusmn0240
21500plusmn0199
22178plusmn0242
Forehead
16805plusmn0125
15723plusmn0205
16235plusmn0241
17659plusmn0225
17505plusmn0263
15788plusmn0168
17763plusmn046
016
319plusmn0482
16620plusmn0461
Highpo
wer
hand
lebar
309527plusmn10
84316942plusmn2200
319095plusmn1144
313476plusmn16
95325003plusmn2085328681plusmn
1642
309170plusmn2816
325744plusmn2808338956plusmn2025PS
Ilowastlowastlowastlowast
ALoclowastlowastlowastlowast
TyrelowastPS
Ilowastlowast
TyrelowastALoclowastlowast
PSIlowast
ALoclowast
Wris
t310326plusmn17
613118
62plusmn19
44319101plusmn
1745
308851plusmn
1646
307399plusmn15
88324736plusmn18
583110
31plusmn16
343252
17plusmn2201
320763plusmn10
01Ank
le320164plusmn2753
307261plusmn
1813
308363plusmn19
35294291plusmn
1562
297999plusmn19
623119
27plusmn1746
299579plusmn4112
287204plusmn1748
3252
10plusmn2184
Seatpo
st343183plusmn2782
339910plusmn2618
3374
90plusmn19
463114
56plusmn2294324106plusmn204
8339546plusmn19
09306605plusmn4610324129plusmn356434364
6plusmn2565
Lumbar
540
80plusmn12
6055831plusmn0971
544
96plusmn1139
53255plusmn13
3454598plusmn12
1254818plusmn12
1248842plusmn0432
46912plusmn0481
53320plusmn0485
Forehead
55814plusmn13
9762502plusmn0620
58694plusmn0998
49398plusmn10
8350786plusmn14
2353796plusmn1525
57876plusmn1741
46845plusmn0808
59633plusmn15
70Where
tyre
(tyre
size)P
SI(ty
reinflatio
npressure)andALoc
(accele
rometer
locatio
n)refertothem
aineffectfor
power
band
Tyrelowast
ALoc
refersto
thetwo-way
interactionbetweentyre
sizea
ndaccelerometer
locatio
nlowastdeno
tessignificance
(119875lt005)lowastlowast(119875lt001)lowastlowastlowast(119875lt0001)lowastlowastlowastlowast(119875lt00001)clubsclubssig
nifiesa
postho
cdifference
(119875lt001)for
lowpo
wer
whencomparedto
cyclo
XKingtyre
sizeotimesotimesotimesotimessig
nifiesa
postho
cdifference
(119875lt00001)for
tyre
inflatio
npressure
whencomparedto
LowPS
Iandoplusoplusoplusoplus(119875lt00001)com
paredto
HighPS
I
Shock and Vibration 9
In the first instance Figure 4 identifies the highly signifi-cant (119875 lt 00001) effect of tyre size on performance timewithregard to normalised tyre inflation pressures This is furtherexacerbated considering the typical tyre inflation pressure(moderate Figure 3) used by competitive XCO-MTB athletes[16] At this pressure post hoc analysis identified differencesbetween 2210158401015840 and 2410158401015840 XKing tyres suggesting that tyre sizecould have considerable effect on performance
While difficult to glean conclusive data regarding overallXCO-MTB performance from such a small downhill com-ponent of performance as collected in this study it is worthnoting that previous research has linked decreased vibrationexposure to increased efficiency [10 11] As such the attenu-ation of accelerations experienced (Figure 5 and Tables 3 and4) at the point of contact between human and bicycle (han-dlebar and seat post) as a result of increased tyre size couldtheoretically be connected to overall performance duringcomplete race distance This obviously assumes that the dec-rease in nonpropulsive work would reduce muscular andcognitive fatigue and consequentially increase performanceHowever it is acknowledged that a complete XCO-MTB raceentails a variety of surfaces and terrains where themajority oftime is spent cycling uphill on smoother surfaces that mightactually suit a smaller higher pressure tyre As such futureresearch is needed to explore this aspect
On the other hand tyre inflation pressure does not seemto influence performance in this experiment (Figure 4) eventhough an increase in accelerations in all axes (Figure 5)related to an increase in magnitude (Table 3) rather than fre-quency (Table 2) was apparent While interesting the tran-sient nature of the protocol used cannot corroborate thelong term effects that racing for ge90mins with the observedincreases in magnitude would have on accumulated muscu-lar fatigue Based on previous laboratorywork [6 19] it is beli-eved that XCO-MTB performance would be compromisedover a complete race distance but requires confirmation
Similar to previous work on the transference of acceler-ations during XCO-MTB [9] the data presented here showsthat both the bicycle and the soft tissue are dissipating energy[20 21] from the interaction of bicycle with surface terrainimplying a reduced nonpropulsive work component of XCO-MTB as a result of increased tyre size This is supportedthrough two-way interactions between both tyre size lowast accel-erometer position and tyre inflation pressure lowast accelero-meter location for total vertical and horizontal accelera-tions (Figure 5) magnitude (Table 3) and low-high powerdistribution (Table 4) As such the reduction in measuresassociated with acceleration exposure reported previouslydecreased at the point of interaction with the bicycle withan increase in tyre size Importantly this was accompaniedby reductions at the soft tissue sites implying a reduced non-propulsive work component of XCO-MTB as a result ofincreased tyre size Alternatively increases in tyre inflationpressure have the opposite and negative effect by increasingrider exposure to accelerations at the point of interface withbicycle and thus increase the non-propulsive componentAdditionally the controlled nature of this protocol mayenable participants to alter body position or riding style
dependent on tyre chracteristics not afforded during a racingsituation
5 Conclusion
This study set out to quantify the influence of tyre size andnormalised tyre inflation pressure on exposure to impactstypical to cross country mountain bike riding It was foundthat the larger the tyre size within the range tested thelower the level of impact exposure experienced at the pointof contact between bicycle and body This reduction meantparticipants performed less non-propulsive muscular workand performed better when compared to a smaller tyre of thesame construction and tread pattern Contrariwise highertyre inflation pressures were associated with an increase inthe level of impact exposure and thus greater soft tissue workin order to attenuate the larger impacts In addition it wasshown that increased tyre inflation pressure could interactnegatively with tyre size while increased tyre size couldinteract positively with tyre inflation pressure As such theeffects of reduced exposure need to be assessed with regardsto longer periods of time such as experienced in a mountainbike race or recreational ride
6 Practical Application
It is recommended that participants (recreational and com-petitive) use a higher volume tyre over any smaller alternativewithin the range tested here In doing so it is suggested thatparticipants could improve performance and likely reducethe risk of overuse injuries or increase the time spent ridingfor the same risk(s)
It is important to note that two-way interactions betweentyre size and tyre inflation pressures suggest that the benefitsof riding with a bigger tyre could be negated through the useof high tyre inflation pressure Conversely the use of lowertyre inflation pressures in smaller tyres could reduce exposurebut must come with a warning of increased unreliability interms of punctures and de-beading from the wheel rim
7 Future Research
The findings of this study must now be verified over a com-plete XCO-MTB race lap consisting of a variety of terrainsto enable whole performance analysis and terrain specificsection performance analysis
Conflict of Interests
The authors declare that there is no conflict of interestsregarding the publication of this paper
References
[1] H THurst and S Atkins ldquoPower output of field-based downhillmountain bikingrdquo Journal of Sports Sciences vol 24 no 10 pp1047ndash1053 2006
[2] F M Impellizzeri and S M Marcora ldquoThe physiology ofmountain bikingrdquo SportsMedicine vol 37 no 1 pp 59ndash71 2007
10 Shock and Vibration
[3] P W Macdermid and S Stannard ldquoMechanical work andphysiological responses to simulated cross country mountainbike racingrdquo Journal of Sports Sciences vol 30 no 14 pp 1491ndash1501 2012
[4] B Stapelfeldt A Schwirtz Y O Schumacher and M Hille-brecht ldquoWorkload demands in mountain bike racingrdquo Interna-tional Journal of Sports Medicine vol 25 no 4 pp 294ndash3002004
[5] P Macdermid P Fink and S Stannard ldquoThe effects of vibra-tions experienced during road vs off-road cyclingrdquo Interna-tional Journal of Sports Medicine 2015
[6] B Samuelson L Jorfeldt and B Ahlborg ldquoInfluence of vibra-tion on endurance of maximal isometric contractionrdquo ClinicalPhysiology vol 9 no 1 pp 21ndash25 1989
[7] J Titlestad A Fairlie-Clarke M Davie A Whittaker and SGrant ldquoExperimental evaluation of mountain bike suspensionsystemsrdquo Acta Polytechnica vol 43 no 5 2003
[8] H T Hurst M Swaren K Hebert-Losier et al ldquoInfluenceof course type on upper body muscle activity in elite Cross-Country andDownhillmountain bikers during offRoadDown-hill Cyclingrdquo Journal of Science and Cycling vol 1 no 2 pp 2ndash92012
[9] P W Macdermid P W Fink and S R Stannard ldquoTransferenceof 3D accelerations during cross country mountain bikingrdquoJournal of Biomechanics vol 47 no 8 pp 1829ndash1837 2014
[10] P W Macdermid P W Fink and S R Stannard ldquoThe effectsof vibrations experienced during road vs off-road cyclingrdquoInternational Journal of Sports Medicine 2015
[11] J Mester P Spitzenfeil J Schwarzer and F Seifriz ldquoBiologicalreaction to vibrationmdashimplications for sportrdquo Journal of Scienceand Medicine in Sport vol 2 no 3 pp 211ndash226 1999
[12] T Ishii Y Umerura and K Kitagawa ldquoInfluences of mountainbike suspension systems on energy supply and performancerdquoJapanese Journal of Biomechanics in Sports and Exercise vol 7pp 2ndash9 2003
[13] L M Sherwin P M O Owende C L Kanali J Lyons and SM Ward ldquoInfluence of tyre inflation pressure on whole-bodyvibrations transmitted to the operator in a cut-to-length timberharvesterrdquoApplied Ergonomics vol 35 no 3 pp 253ndash261 2004
[14] J Gordon J J Kauzlarich and J G Thacker ldquoTests of two newpolyurethane foam wheelchair tiresrdquo Journal of RehabilitationResearch and Development vol 26 no 1 pp 33ndash46 1989
[15] B J Sawatzky W O Kim and I Denison ldquoThe ergonomics ofdifferent tyres and tyre pressure during wheelchair propulsionrdquoErgonomics vol 47 no 14 pp 1475ndash1483 2004
[16] PWMacdermid PW Fink and S R Stannard ldquoThe influenceof tyre characteristics on measures of rolling performance dur-ing cross-country mountain bikingrdquo Journal of Sports Sciencesvol 33 no 3 pp 277ndash285 2015
[17] R Van der Plas Bicycle Technology Motorbooks International1991
[18] M Munera X Chiementin S Crequy and W Bertucci ldquoPhys-ical risk associated with vibration at cyclingrdquo Mechanics ampIndustry vol 15 no 6 pp 535ndash540 2014
[19] J Titlestad T Fairlie-Clarke A Whittaker M Davie I Wattand S Grant ldquoEffect of suspension systems on the physiologicaland psychological responses to sub-maximal biking on simu-lated smoothand bumpy tracksrdquo Journal of Sports Sciences vol24 no 2 pp 125ndash135 2006
[20] V B Issurin ldquoVibrations and their applications in sport areviewrdquo Journal of Sports Medicine and Physical Fitness vol 45no 3 pp 324ndash336 2005
[21] M Levy and G A Smith ldquoEffectiveness of vibration dampingwith bicycle suspension systemsrdquo Sports Engineering vol 8 no2 pp 99ndash106 2005
International Journal of
AerospaceEngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
RoboticsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Active and Passive Electronic Components
Control Scienceand Engineering
Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
International Journal of
RotatingMachinery
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporation httpwwwhindawicom
Journal ofEngineeringVolume 2014
Submit your manuscripts athttpwwwhindawicom
VLSI Design
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Shock and Vibration
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Civil EngineeringAdvances in
Acoustics and VibrationAdvances in
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Electrical and Computer Engineering
Journal of
Advances inOptoElectronics
Hindawi Publishing Corporation httpwwwhindawicom
Volume 2014
The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014
SensorsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Modelling amp Simulation in EngineeringHindawi Publishing Corporation httpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Chemical EngineeringInternational Journal of Antennas and
Propagation
International Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Navigation and Observation
International Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
DistributedSensor Networks
International Journal of
Shock and Vibration 9
In the first instance Figure 4 identifies the highly signifi-cant (119875 lt 00001) effect of tyre size on performance timewithregard to normalised tyre inflation pressures This is furtherexacerbated considering the typical tyre inflation pressure(moderate Figure 3) used by competitive XCO-MTB athletes[16] At this pressure post hoc analysis identified differencesbetween 2210158401015840 and 2410158401015840 XKing tyres suggesting that tyre sizecould have considerable effect on performance
While difficult to glean conclusive data regarding overallXCO-MTB performance from such a small downhill com-ponent of performance as collected in this study it is worthnoting that previous research has linked decreased vibrationexposure to increased efficiency [10 11] As such the attenu-ation of accelerations experienced (Figure 5 and Tables 3 and4) at the point of contact between human and bicycle (han-dlebar and seat post) as a result of increased tyre size couldtheoretically be connected to overall performance duringcomplete race distance This obviously assumes that the dec-rease in nonpropulsive work would reduce muscular andcognitive fatigue and consequentially increase performanceHowever it is acknowledged that a complete XCO-MTB raceentails a variety of surfaces and terrains where themajority oftime is spent cycling uphill on smoother surfaces that mightactually suit a smaller higher pressure tyre As such futureresearch is needed to explore this aspect
On the other hand tyre inflation pressure does not seemto influence performance in this experiment (Figure 4) eventhough an increase in accelerations in all axes (Figure 5)related to an increase in magnitude (Table 3) rather than fre-quency (Table 2) was apparent While interesting the tran-sient nature of the protocol used cannot corroborate thelong term effects that racing for ge90mins with the observedincreases in magnitude would have on accumulated muscu-lar fatigue Based on previous laboratorywork [6 19] it is beli-eved that XCO-MTB performance would be compromisedover a complete race distance but requires confirmation
Similar to previous work on the transference of acceler-ations during XCO-MTB [9] the data presented here showsthat both the bicycle and the soft tissue are dissipating energy[20 21] from the interaction of bicycle with surface terrainimplying a reduced nonpropulsive work component of XCO-MTB as a result of increased tyre size This is supportedthrough two-way interactions between both tyre size lowast accel-erometer position and tyre inflation pressure lowast accelero-meter location for total vertical and horizontal accelera-tions (Figure 5) magnitude (Table 3) and low-high powerdistribution (Table 4) As such the reduction in measuresassociated with acceleration exposure reported previouslydecreased at the point of interaction with the bicycle withan increase in tyre size Importantly this was accompaniedby reductions at the soft tissue sites implying a reduced non-propulsive work component of XCO-MTB as a result ofincreased tyre size Alternatively increases in tyre inflationpressure have the opposite and negative effect by increasingrider exposure to accelerations at the point of interface withbicycle and thus increase the non-propulsive componentAdditionally the controlled nature of this protocol mayenable participants to alter body position or riding style
dependent on tyre chracteristics not afforded during a racingsituation
5 Conclusion
This study set out to quantify the influence of tyre size andnormalised tyre inflation pressure on exposure to impactstypical to cross country mountain bike riding It was foundthat the larger the tyre size within the range tested thelower the level of impact exposure experienced at the pointof contact between bicycle and body This reduction meantparticipants performed less non-propulsive muscular workand performed better when compared to a smaller tyre of thesame construction and tread pattern Contrariwise highertyre inflation pressures were associated with an increase inthe level of impact exposure and thus greater soft tissue workin order to attenuate the larger impacts In addition it wasshown that increased tyre inflation pressure could interactnegatively with tyre size while increased tyre size couldinteract positively with tyre inflation pressure As such theeffects of reduced exposure need to be assessed with regardsto longer periods of time such as experienced in a mountainbike race or recreational ride
6 Practical Application
It is recommended that participants (recreational and com-petitive) use a higher volume tyre over any smaller alternativewithin the range tested here In doing so it is suggested thatparticipants could improve performance and likely reducethe risk of overuse injuries or increase the time spent ridingfor the same risk(s)
It is important to note that two-way interactions betweentyre size and tyre inflation pressures suggest that the benefitsof riding with a bigger tyre could be negated through the useof high tyre inflation pressure Conversely the use of lowertyre inflation pressures in smaller tyres could reduce exposurebut must come with a warning of increased unreliability interms of punctures and de-beading from the wheel rim
7 Future Research
The findings of this study must now be verified over a com-plete XCO-MTB race lap consisting of a variety of terrainsto enable whole performance analysis and terrain specificsection performance analysis
Conflict of Interests
The authors declare that there is no conflict of interestsregarding the publication of this paper
References
[1] H THurst and S Atkins ldquoPower output of field-based downhillmountain bikingrdquo Journal of Sports Sciences vol 24 no 10 pp1047ndash1053 2006
[2] F M Impellizzeri and S M Marcora ldquoThe physiology ofmountain bikingrdquo SportsMedicine vol 37 no 1 pp 59ndash71 2007
10 Shock and Vibration
[3] P W Macdermid and S Stannard ldquoMechanical work andphysiological responses to simulated cross country mountainbike racingrdquo Journal of Sports Sciences vol 30 no 14 pp 1491ndash1501 2012
[4] B Stapelfeldt A Schwirtz Y O Schumacher and M Hille-brecht ldquoWorkload demands in mountain bike racingrdquo Interna-tional Journal of Sports Medicine vol 25 no 4 pp 294ndash3002004
[5] P Macdermid P Fink and S Stannard ldquoThe effects of vibra-tions experienced during road vs off-road cyclingrdquo Interna-tional Journal of Sports Medicine 2015
[6] B Samuelson L Jorfeldt and B Ahlborg ldquoInfluence of vibra-tion on endurance of maximal isometric contractionrdquo ClinicalPhysiology vol 9 no 1 pp 21ndash25 1989
[7] J Titlestad A Fairlie-Clarke M Davie A Whittaker and SGrant ldquoExperimental evaluation of mountain bike suspensionsystemsrdquo Acta Polytechnica vol 43 no 5 2003
[8] H T Hurst M Swaren K Hebert-Losier et al ldquoInfluenceof course type on upper body muscle activity in elite Cross-Country andDownhillmountain bikers during offRoadDown-hill Cyclingrdquo Journal of Science and Cycling vol 1 no 2 pp 2ndash92012
[9] P W Macdermid P W Fink and S R Stannard ldquoTransferenceof 3D accelerations during cross country mountain bikingrdquoJournal of Biomechanics vol 47 no 8 pp 1829ndash1837 2014
[10] P W Macdermid P W Fink and S R Stannard ldquoThe effectsof vibrations experienced during road vs off-road cyclingrdquoInternational Journal of Sports Medicine 2015
[11] J Mester P Spitzenfeil J Schwarzer and F Seifriz ldquoBiologicalreaction to vibrationmdashimplications for sportrdquo Journal of Scienceand Medicine in Sport vol 2 no 3 pp 211ndash226 1999
[12] T Ishii Y Umerura and K Kitagawa ldquoInfluences of mountainbike suspension systems on energy supply and performancerdquoJapanese Journal of Biomechanics in Sports and Exercise vol 7pp 2ndash9 2003
[13] L M Sherwin P M O Owende C L Kanali J Lyons and SM Ward ldquoInfluence of tyre inflation pressure on whole-bodyvibrations transmitted to the operator in a cut-to-length timberharvesterrdquoApplied Ergonomics vol 35 no 3 pp 253ndash261 2004
[14] J Gordon J J Kauzlarich and J G Thacker ldquoTests of two newpolyurethane foam wheelchair tiresrdquo Journal of RehabilitationResearch and Development vol 26 no 1 pp 33ndash46 1989
[15] B J Sawatzky W O Kim and I Denison ldquoThe ergonomics ofdifferent tyres and tyre pressure during wheelchair propulsionrdquoErgonomics vol 47 no 14 pp 1475ndash1483 2004
[16] PWMacdermid PW Fink and S R Stannard ldquoThe influenceof tyre characteristics on measures of rolling performance dur-ing cross-country mountain bikingrdquo Journal of Sports Sciencesvol 33 no 3 pp 277ndash285 2015
[17] R Van der Plas Bicycle Technology Motorbooks International1991
[18] M Munera X Chiementin S Crequy and W Bertucci ldquoPhys-ical risk associated with vibration at cyclingrdquo Mechanics ampIndustry vol 15 no 6 pp 535ndash540 2014
[19] J Titlestad T Fairlie-Clarke A Whittaker M Davie I Wattand S Grant ldquoEffect of suspension systems on the physiologicaland psychological responses to sub-maximal biking on simu-lated smoothand bumpy tracksrdquo Journal of Sports Sciences vol24 no 2 pp 125ndash135 2006
[20] V B Issurin ldquoVibrations and their applications in sport areviewrdquo Journal of Sports Medicine and Physical Fitness vol 45no 3 pp 324ndash336 2005
[21] M Levy and G A Smith ldquoEffectiveness of vibration dampingwith bicycle suspension systemsrdquo Sports Engineering vol 8 no2 pp 99ndash106 2005
International Journal of
AerospaceEngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
RoboticsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Active and Passive Electronic Components
Control Scienceand Engineering
Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
International Journal of
RotatingMachinery
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporation httpwwwhindawicom
Journal ofEngineeringVolume 2014
Submit your manuscripts athttpwwwhindawicom
VLSI Design
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Shock and Vibration
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Civil EngineeringAdvances in
Acoustics and VibrationAdvances in
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Electrical and Computer Engineering
Journal of
Advances inOptoElectronics
Hindawi Publishing Corporation httpwwwhindawicom
Volume 2014
The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014
SensorsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Modelling amp Simulation in EngineeringHindawi Publishing Corporation httpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Chemical EngineeringInternational Journal of Antennas and
Propagation
International Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Navigation and Observation
International Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
DistributedSensor Networks
International Journal of
10 Shock and Vibration
[3] P W Macdermid and S Stannard ldquoMechanical work andphysiological responses to simulated cross country mountainbike racingrdquo Journal of Sports Sciences vol 30 no 14 pp 1491ndash1501 2012
[4] B Stapelfeldt A Schwirtz Y O Schumacher and M Hille-brecht ldquoWorkload demands in mountain bike racingrdquo Interna-tional Journal of Sports Medicine vol 25 no 4 pp 294ndash3002004
[5] P Macdermid P Fink and S Stannard ldquoThe effects of vibra-tions experienced during road vs off-road cyclingrdquo Interna-tional Journal of Sports Medicine 2015
[6] B Samuelson L Jorfeldt and B Ahlborg ldquoInfluence of vibra-tion on endurance of maximal isometric contractionrdquo ClinicalPhysiology vol 9 no 1 pp 21ndash25 1989
[7] J Titlestad A Fairlie-Clarke M Davie A Whittaker and SGrant ldquoExperimental evaluation of mountain bike suspensionsystemsrdquo Acta Polytechnica vol 43 no 5 2003
[8] H T Hurst M Swaren K Hebert-Losier et al ldquoInfluenceof course type on upper body muscle activity in elite Cross-Country andDownhillmountain bikers during offRoadDown-hill Cyclingrdquo Journal of Science and Cycling vol 1 no 2 pp 2ndash92012
[9] P W Macdermid P W Fink and S R Stannard ldquoTransferenceof 3D accelerations during cross country mountain bikingrdquoJournal of Biomechanics vol 47 no 8 pp 1829ndash1837 2014
[10] P W Macdermid P W Fink and S R Stannard ldquoThe effectsof vibrations experienced during road vs off-road cyclingrdquoInternational Journal of Sports Medicine 2015
[11] J Mester P Spitzenfeil J Schwarzer and F Seifriz ldquoBiologicalreaction to vibrationmdashimplications for sportrdquo Journal of Scienceand Medicine in Sport vol 2 no 3 pp 211ndash226 1999
[12] T Ishii Y Umerura and K Kitagawa ldquoInfluences of mountainbike suspension systems on energy supply and performancerdquoJapanese Journal of Biomechanics in Sports and Exercise vol 7pp 2ndash9 2003
[13] L M Sherwin P M O Owende C L Kanali J Lyons and SM Ward ldquoInfluence of tyre inflation pressure on whole-bodyvibrations transmitted to the operator in a cut-to-length timberharvesterrdquoApplied Ergonomics vol 35 no 3 pp 253ndash261 2004
[14] J Gordon J J Kauzlarich and J G Thacker ldquoTests of two newpolyurethane foam wheelchair tiresrdquo Journal of RehabilitationResearch and Development vol 26 no 1 pp 33ndash46 1989
[15] B J Sawatzky W O Kim and I Denison ldquoThe ergonomics ofdifferent tyres and tyre pressure during wheelchair propulsionrdquoErgonomics vol 47 no 14 pp 1475ndash1483 2004
[16] PWMacdermid PW Fink and S R Stannard ldquoThe influenceof tyre characteristics on measures of rolling performance dur-ing cross-country mountain bikingrdquo Journal of Sports Sciencesvol 33 no 3 pp 277ndash285 2015
[17] R Van der Plas Bicycle Technology Motorbooks International1991
[18] M Munera X Chiementin S Crequy and W Bertucci ldquoPhys-ical risk associated with vibration at cyclingrdquo Mechanics ampIndustry vol 15 no 6 pp 535ndash540 2014
[19] J Titlestad T Fairlie-Clarke A Whittaker M Davie I Wattand S Grant ldquoEffect of suspension systems on the physiologicaland psychological responses to sub-maximal biking on simu-lated smoothand bumpy tracksrdquo Journal of Sports Sciences vol24 no 2 pp 125ndash135 2006
[20] V B Issurin ldquoVibrations and their applications in sport areviewrdquo Journal of Sports Medicine and Physical Fitness vol 45no 3 pp 324ndash336 2005
[21] M Levy and G A Smith ldquoEffectiveness of vibration dampingwith bicycle suspension systemsrdquo Sports Engineering vol 8 no2 pp 99ndash106 2005
International Journal of
AerospaceEngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
RoboticsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Active and Passive Electronic Components
Control Scienceand Engineering
Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
International Journal of
RotatingMachinery
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporation httpwwwhindawicom
Journal ofEngineeringVolume 2014
Submit your manuscripts athttpwwwhindawicom
VLSI Design
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Shock and Vibration
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Civil EngineeringAdvances in
Acoustics and VibrationAdvances in
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Electrical and Computer Engineering
Journal of
Advances inOptoElectronics
Hindawi Publishing Corporation httpwwwhindawicom
Volume 2014
The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014
SensorsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Modelling amp Simulation in EngineeringHindawi Publishing Corporation httpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
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Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Modelling amp Simulation in EngineeringHindawi Publishing Corporation httpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Chemical EngineeringInternational Journal of Antennas and
Propagation
International Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Navigation and Observation
International Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
DistributedSensor Networks
International Journal of
