comparação de diferentes testes de campo

COMPARISON OF THE CAPACITY OF DIFFERENTJUMP AND SPRINT FIELD TESTS TO DETECTNEUROMUSCULAR FATIGUEROB J. GATHERCOLE, BEN C. SPORER, TRENT STELLINGWERFF, AND GORD G. SLEIVERT

School of Exercise Science, Physical and Health Education, University of Victoria, Victoria, British Columbia, Canada

ABSTRACT

Gathercole, RJ, Sporer, BC, Stellingwerff, T, and Sleivert,

GG. Comparison of the capacity of different jump and sprint

field tests to detect neuromuscular fatigue. J Strength Cond

Res 29(9): 25222531, 2015Different jump and sprint

tests have been used to assess neuromuscular fatigue, but

the test with optimal validity remains to be established. The

current investigation examined the suitability of vertical jump

(countermovement jump [CMJ], squat jump [SJ], drop jump

[DJ]) and 20-m sprint (SPRINT) testing for neuromuscular

fatigue detection. On 6 separate occasions, 11 male team-

sport athletes performed 6 CMJ, SJ, DJ, and 3 SPRINT trials.

Repeatability was determined on the first 3 visits, with sub-

sequent 3 visits (0-, 24-, and 72-hour postexercise)

following a fatiguing Yo-Yo running protocol. SPRINT per-

formance was most repeatable (mean coefficient of variation

#2%), whereas DJ testing (4.8%) was significantly less

repeatable than CMJ (3.0%) and SJ (3.5%). Each test dis-

played large decreases at 0-hour (33 of 49 total variables;

mean effect size = 1.82), with fewer and smaller decreases

at 24-hour postexercise (13 variables; 0.75), and 72-hour

postexercise (19 variables; 0.78). SPRINT displayed the

largest decreases at 0-hour (3.65) but was subsequently

unchanged, whereas SJ performance recovered by

72-hour postexercise. In contrast, CMJ and DJ performance

displayed moderate (12 variables; 1.18) and small (6 varia-

bles; 0.53) reductions at 72-hour postexercise, respectively.

Consequently, the high repeatability and immediate and pro-

longed fatigue-induced changes indicated CMJ testing as

most suitable for neuromuscular fatigue monitoring.

KEY WORDS reliability, fatigue sensitivity, athlete monitoring

INTRODUCTION

Although performance in the activity itself has beensuggested to be the most specific indicator of anathletes sport specific neuromuscular perfor-mance readiness (9), its longitudinal assessment

can be impractical, may impede adaptation, induce unduefatigue, and may not reflect all aspects of an athletes phys-iological and neuromuscular state. Alternatively, field tests ofneuromuscular function have been suggested as suitablemeans of neuromuscular assessment available to practi-tioners (2). Effective monitoring requires valid, reliable, andsufficiently sensitive tests to discern the functional changesthat will impact performance (37). Test validity is influencedby the specificity of movement pattern and contraction typein accordance with the demands of athletes sport (25). Iso-inertial testing, defined as the movement of a constant grav-itational load (31), is therefore considered one of the morevalid forms of neuromuscular testing (28) owing to its sim-ilarities with movements involved in athletic performance.Sprint (20-m sprint test; SPRINT) and vertical jump

testing, such as the countermovement jump (CMJ), squatjump (SJ), and drop jump (DJ), are popular isoinertial field-tests of neuromuscular function (40). The usefulness of jumptests also seems enhanced by the convenient and detailedanalysis of kinetic and kinematic variables provided by forceplate and position transducer systems, which may permitgreater insight into the neuromuscular responses associatedwith neuromuscular fatigue.The sensitivity of these tests to neuromuscular fatigue

remains unclear, with previous investigations reporting con-flicting findings. For example, a muscle-damaging exerciseprotocol elicited the greatest reductions in SJ performancecompared with both CMJ and DJ (13). Conversely, decreaseswere more marked in CMJ and DJ performance after a test-simulating soccer performance, whereas sprint performancewas unchanged (35). Extrapolation of these results is alsolimited by the assessment of immediate (,24 hours)fatigue-induced changes only (35), unrepresentative exerciseprotocols (e.g., 100 barbell squats) (13), and the analysis ofjump performance through jump height (13) and force-relatedvariables (35) only. Similarly, although decreased sprint per-formance has been reported immediately postexercise

Address correspondence to Rob Gathercole, [email protected].

29(9)/25222531

Journal of Strength and Conditioning Research 2015 National Strength and Conditioning Association

2522 Journal of Strength and Conditioning Researchthe TM

Copyright National Strength and Conditioning Association Unauthorized reproduction of this article is prohibited.

(4,20,30), it may recover rapidly (i.e., ,5 hours) (4) and somay be of limited value when monitoring neuromuscularfatigue beyond acute postexercise assessment.The purpose of the investigation was to examine the

validity of the CMJ, SJ, DJ, and SPRINT tests for thedetection of neuromuscular fatigue after a fatiguing exer-cise bout representative of team-sport performance.Assessment of neuromuscular variables associated witheach test was performed 0-, 24-, and 72-hour postexerciseto provide a clearer representation of the sensitivity ofeach test for neuromuscular fatigue detection. We hypoth-esized that the CMJ test would exhibit the greatestsensitivity to neuromuscular fatigue, owing to the com-prehensive neuromuscular assessment it permits and itshigh ecological validity.

METHODS

Experimental Approach to the Problem

A two-part experimental design was implemented to examinethe suitability of the 4 tests for the detection of fatigue-induced declines in neuromuscular function. In part 1, weexamined the intraday and interday repeatability (days 15),whereas in part 2, we looked at the sensitivity to fatigue-induced changes in neuromuscular function (days 69;Figure 1). Participants visited the testing facility at the sametime of day (61.5 hours) on 7 total occasions, featuringa familiarization, 3 separate repeatability testing days, a fatigueprotocol and immediate postexercise assessment, and then 2subsequent days of postfatigue monitoring (Figure 1). Partic-ipants did not perform any additional exercise beyond therequirements of this investigation throughout the course oftesting. As fully described below, participants performed, in

order, SPRINT (3 trials), then CMJ, SJ, and DJ (6 trials each)testing during each session.

Subjects

Eleven male collegiate level team-sport athletes (mean 6SD: 23.8 6 3.9 yrs, 182 6 6 cm, and 80.3 6 6.6 kg) partic-ipated in the study. Eight participants (23.0 6 3.7 yrs, 184 66 cm, and 80.6 6 6.2 kg) completed both repeatability andfatigue sensitivity portions of the study, whereas 3 completedthe repeatability section only. Ethical approval was obtainedfrom the University of Victoria Human Ethics Review Board,with participants providing written informed consent, com-pleting a Physical Activity Readiness Questionnaire anda familiarization session at least 7 days before study com-mencement. Participants adopted a high carbohydrate dietthroughout testing, consuming the same meal, at the sametime, before every testing session. Familiarization consistedof a warm-up and then practice of the 4 tests, with subjectcomfort and consistency of performance emphasized witheach test. A participant was deemed sufficiently familiarizedwhen consistency was demonstrated in the tests performed.For the jumping tests, in addition to visual inspection, con-sistency was determined as peak and minimum displacementand peak power values within 10% for 4 repeated jump trials.This standardized threshold was used to ensure that all par-ticipants displayed relatively similar degrees of movementconsistency at the start of the investigation in the most non-biased way possible.

Testing Sessions

Participants performed a standardized, and repeated, 20-minute dynamic warm-up consisting of light jogging(;10 minutes), dynamic stretching, 10-m and 20-m sprints

(5 each) of progressive speedcompleted within 5 minutes.Between warm-up andSPRINT testing, and betweenall other tests, participantsactively rested for 5 minutes.In the first 2 minutes (of 5 mi-nutes total) before jump testing,participants performed 10 sub-maximal practice trials ofincreasing intensity.

SPRINT Test. SPRINT testingwas performed outside ona marked standardized con-crete track. Sprint time wasmeasured using timing gates(Brower ID XS Training Sys-tem; Brower Timing Systems,Draper, UT, USA) placed at 0,10, and 20 m, allowing mea-surement of 010 m, 1020 m,and 020 m time. Participants

Figure 1. A) Schematic representation of the study timeline including familiarization, repeatability(i.e., Reliability), and fatigue sensitivity portions; (B) the fatigue protocol. CMJ = countermovement jump.

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VOLUME 29 | NUMBER 9 | SEPTEMBER 2015 | 2523


began in a standing position with their forward foot 0.5 mbehind the 0-m timing gates. Participants performed 3SPRINT trials and recovered between each sprint by walk-ing back to the start-line with a total of 1.5 minutesbetween each trial.

Vertical Jump Tests. After SPRINT testing, participantsperformed 6 trials of each CMJ, SJ, and DJ, with1.5 minutes rest between each trial and 5 minutes betweeneach test. Trials were sampled at 200 Hz using the BallisticMeasurement System software (BMS; Fitness Technology,Adelaide, Australia; version 2012.3.7), consisting of a forceplate (400 series, Fitness Technology, Adelaide, Australia)and position transducer (Celesco, PT5A-0150-V62-UP-1K-M6, Chatsworth, CA, USA). Excluding DJ testing(consisting of force plate only), CMJ and SJ testing useda ceiling-mounted position transducer suspended directlyabove the force plate and attached to the center ofa wooden dowel placed on participants back similar toa back squat. Participants were instructed to limit dowel

movement, with the position transducer zeroed toparticipant height before every jump. Data were col-lected immediately after zeroing until the jump wascompleted. For CMJ testing, participants were directedto perform the CMJ as they normally would witha quick countermovement to a comfortable depthemphasized. Squat jump testing began with the partici-pant in a squat position at a self-selected depth of ;908,holding this position for a researchers count of 3, beforejumping. If a dipping movement was evident in the BMSvelocity trace (i.e., ,20.05 m$s21 change), then the trialwas repeated. For the DJ, participants began by standingon a platform 35 cm above the force plate, with handsplaced on hips. Participants then stepped off the plat-form, landing on the force plate before jumping as highas possible while keeping hands on hips. Participantswere directed to step, not jump, off the platform, andto jump as high and as quickly as possible. Before eachjump test, participants performed 10 practice trials ofincreasing intensity.

TABLE 1. Description of (A) typical (CMJ-TYP) and (B) alternative (CMJ-ALT) CMJ variables, and (C) SJ-specificvariables and associated abbreviations.*

Abbreviations Description

A Peak power PP Greatest power achieved during the jumpMean power MP Mean power (concentric phase only)Maximum rate of powerdevelopment

MaxRPD Greatest rate of power increase during a 30-millisecond epoch

Time to peak power TTPP Time from jump initiation to peak powerPeak force PF Greatest force achieved during the jumpMean force MF Mean force (concentric phase only)Maximum rate of forcedevelopment

MaxRFD Greatest rate of force increase during a 30-millisecond epoch

Time to peak force TTPF Time from jump initiation to peak forceTotal impulse TI Total force exerted multiplied by time taken (concentric phase only)Peak velocity PV Greatest velocity achieved during the jumpMinimum velocity MinV Peak eccentric velocityVelocity at peak power V@PP Velocity recorded at peak powerFlight time FT Time spent in the air from jump take-off to landingFlight time:contraction time FT:CT Ratio of flight-to-contraction time. Contraction time is the duration

from jump initiation to take-offJump height JH Maximum jump height (calculated using peak velocity)

B Force at zero velocity F@0V Force exerted at concentric phase onset (i.e., velocity is at zero)Area under the force velocitytrace

FV-AUC Area under the eccentric phase of the force-velocity trace

Eccentric duration EccDur Duration of the eccentric CMJ phaseConcentric duration ConDur Duration of the concentric CMJ phaseTotal duration TotDur Duration of the entire CMJMean eccentric andconcentric power overtime

EccConMP Mean power (during both eccentric and concentric phases; eccentricpower converted to absolute values) divided by the total duration (inmilliseconds) of the jump

C Peak displacement PD Greatest displacement recorded during the jumpMinimum displacement MinD Lowest displacement recorded during the jump

*CMJ = countermovement jump.

Jump and sprint testing to detect neuromuscular fatigue



Fatiguing Protocol

A 3-stage Yo-Yo fatiguing protocol (Figure 1) was performedon an outdoor concrete track to elicit a neuromuscular loadsimilar to team-sport activities (Yo-Yo intermittent recoverylevel 2 [Yo-Yo IR 2] and Yo-Yo intermittent endurance level 2[Yo-Yo IE 2] tests (7)). Briefly, the Yo-Yo IR 2 was performedtwice consecutively and involved repeated 20-m shuttle runsperformed at increasing velocities (10-second recoveries). Yo-Yo IE 2, performed once, involved 20-m shuttle runs at slowervelocities (5-second recoveries). As the purpose of the fatiguingprotocol was to elicit fatigue and not to infer physiologicalcapacity, in the final stages, participants were encouraged tocontinue performing each Yo-Yo test regardless of whethershuttle runs were made within the allotted time. Therefore,participants volitionally terminating exercise only once theyhad determined themselves unable to carry on. Between Yo-Yo tests, participants performed 5 minutes of active recovery,

walking around and avoiding sitting down, with water pro-vided ad libitum. Following the fatigue protocol, participantsperformed 5 minutes of active recovery, before beginning thetest session (i.e., SPRINT, CMJ, SJ, and DJ testing).

Vertical Jump Test Variables

Ballistic Measurement System software was used to deter-mine all SJ, DJ, and typically-derived CMJ variables (CMJ-TYP). Countermovement jump alternative (CMJ-ALT)variables were calculated using previous methods (18,19).Force and power (mean and peak) values were convertedto values relative to body mass. Description of all variablescan be found in (Table 1).

Statistical Analyses

For all vertical jump tests, the 4 most consistent trials fromthe 6 collected were used in further analysis, as has beenused previously (18,19). Countermovement jump trial

Figure 2. Mean percentage and 90% confidence intervals for the intrasession (white markers) and intersession (black markers) CV for CMJ (squares), SJ(triangles), and DJ (circles) testing. Significant between-test differences (above in black; #p # 0.05 vs. CMJ; *p # 0.05 vs. SJ) and the magnitude of effect (ES)between tests (below in gray; ^ indicates $moderate ES vs. CMJ; $ indicates $moderate ES vs. SJ) are shown. CV = coefficient of variation; CMJ =countermovement jump; SJ = squat jump; DJ = drop jump; ES = effect size.


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selection was based on the variable EccConMP (Table 1),whereas SJ and DJ trials were both determined by calculat-ing the peak power divided by the duration of the jump. The

4 most consistent jumps were identified by subtracting thesevalues by the mean of all 6 trials and determining the 4 trialswith the smallest difference.

Figure 3. Fatigue sensitivity 90% CIs of the ES for the group changes in CMJ, DJ, SJ, and 20-m sprint test variables at 0-, 24-, and 72-hour postexercise. BoldCIs signify a substantial change (i.e., that mean ES was greater than60.9 (moderate ES; indicated by asterisks), or the ES CI does not extend across both trivialES boundaries (60.3; indicated by hash). Black and gray CIs illustrate changes indicative of diminished or improved neuromuscular function, respectively. CI =confidence interval; ES = effect size; CMJ = countermovement jump; DJ = drop jump; SJ = squat jump.




Coefficient of variation (CV) was calculated using rawdata collected during prefatigue testing days only. The meanof each within-day CVwas used to calculate intrasession CV,whereas intersession CVwas determined using results (meanand SD) from each testing day. Between-test differences anddifferences in intrasession and intersession repeatability wereexamined using CVs for the same neuromuscular variablesderived from each vertical jump test. Significant differenceswere examined through linear mixed modeling (IBM SPSSStatistics, version 20, IBM Corp., Armonk, NY, USA),whereas effect sizes (ES) based on between-subject SD, withappropriate inferences (21), were calculated to examine themagnitude of difference. An ES of moderate or greater (i.e.,60.6) was used to indicate a substantial change.To examine fatigue sensitivity, data were log-transformed,

and then ES (mean and 90% confidence intervals [CIs]) werecalculated for postfatigue changes (i.e., 0-, 24-, and 72-hourpostexercise). Effect sizes were based on typical within-individual variability (i.e., mean interday CV), with CVmultiplied by 0.3, 0.9, and 1.6 for small, moderate, and largeeffects, respectively (40). For the fatigue analyses and pre-exercise time point, the results of day 3 were used andreferred to as baseline. A substantial change was deter-mined as either an ES of moderate or greater (i.e., 60.9)or a small mean ES with CIs that did not extend across bothtrivial boundaries (i.e., 60.3).

RESULTS

Test Repeatability

No significant or substantial differences were evidentbetween intrasession and intersession CV of the samevariables (i.e., intrasession CMJ peak power CV vs. interses-sion CMJ peak power CV; Figure 2). SPRINT performancewas most repeatable, with CVs of 2% or less. SPRINT per-formance intrasession CVs (mean 6 SD) for 010 m, 1020m, and 020 m time were 1.3 6 0.1, 2.0 6 0.6, and 0.9 6 0.1,whereas intersession CVs were 1.0 6 0.7, 1.3 6 0.9, and0.8 6 0.4, respectively. For vertical jump test comparisons(Figure 2), the same trends were apparent in both intrases-sion and intersession repeatability, with DJ testing associatedwith the largest CVs (mean 6 SD: 4.8 6 1.7), whereas theCV in CMJ (3.0 6 1.1) and SJ (3.5 6 1.6) testing weregenerally very similar. Drop jump testing CVs were substan-tially larger (.CV) in all but 1 intrasession comparison and 7of 18 intersession comparisons.

Fatigue Sensitivity

Distance covered during the fatigue protocol was 8613 61249 m. Postexercise test results are shown in Figure 3.Although 3 variables displayed small (mean ES, describedwithout direction; 0.66) improvements in function, wide-spread decreases were evident at 0-hour with 33 variables(of 49 in total) displaying large decreases (1.82). By 24-hour,13 variables remained substantially decreased to a small extent(0.75). Nineteen variables were substantially diminished at

72-hour again to a small extent (0.78), whereas 6 variablesexhibited moderate improvement (1.11).Moderate decreases (1.17) were evident in most CMJ

variables at 0-hour (13 of 21). By 24-hour, 6 CMJ variables(MP, TTPP, MaxRFD, V@PP, FT, and EccConMP) dis-played small decreases in function (0.89), whereas TIdisplayed small improvement (0.43). At 72-hour, 3 CMJvariables (TI, MinV, and FV-AUC) exhibited moderatelyimproved function (1.41), whereas 12 variables, reflectingtime, force, and eccentric function, displayed moderatelydiminished function (1.18).Three SJ variables (PF, TTPP, and TTPF) displayed

small improvements (0.66) immediately postexercise,whereas 8 variables (of 16), representing power, velocity,displacement, and flight time, were moderately diminished(1.18). At 24-hour, 5 SJ variables (PP, PV, PD, FT, and JH)exhibited small decreases (0.75), whereas only FT wasreduced at 72-hour (0.64).All DJ variables (9 in total), excluding TI, were at least

moderately diminished at 0-hour (1.28). At 24-hour, only FTand FT:CT displayed small reductions (0.63), whereas TIwas increased to a small extent (0.48). Like CMJ results, 6 DJvariables, relating to power, velocity and flight time, againdisplayed small decreases (0.53) at 72-hour.SPRINT variables displayed the most substantial imme-

diate decreases (mean ES = 3.65). By 24-hour, no differenceswere evident, with moderate improvements (1.08) in 2 var-iables at 72-hour.

DISCUSSION

Although this is not the first investigation to comparefatigue-induced changes in vertical jump and SPRINT testperformance (13,35), this study extends the knowledge gen-erated in previous investigations by (a) the between-testcomparison of intraday and interday repeatability, (b) a com-prehensive analysis of neuromuscular variables from eachtest, and (c) a longer 72-hour postfatigue assessment forcomparison of neuromuscular function both immediatelyand during the secondary recovery phase. Results indicatethat the repeatability of the same neuromuscular constructs(i.e., power, force, velocity) differs between tests, with CMJand SJ performance more repeatable than DJ testing.SPRINT performance displayed the greatest repeatabilityoverall, with large immediate postexercise decreases alsoevident (Figure 3). However, by 72-hour, only CMJ and DJtest performance remained diminished, suggesting that thesetests offer superior prolonged sensitivity to altered neuro-muscular function and, conceivably, neuromuscular fatigue.Previous neuromuscular repeatability investigations have

considered a ,10% CV as indicative of a repeatable test(15,39). Performance in each test examined here can thusbe considered sufficiently repeatable. We used standardizedjump trial selection criteria (selecting the 4 most consistentjumps of 6, with no researcher interpretation) to enhance therepeatability of the jump tests, which would theoretically


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result in lower CVs in the current study. As with all CVcalculations, our results are unique to the specifics of theinvestigation (e.g., participants or population examined, pro-cedures used); however, the repeatability of jump perfor-mance determined here could thus be consideredartificially high. Moreover, a test with very low measurementof CV might also theoretically lack sensitivity to detectchanges in neuromuscular function, whereas these methodsmay obscure differences in the variability of jump perfor-mance, which may be an important feature of neuromuscu-lar function. Consequently, despite the seemingly enhancedconsistency of jump performance data, it is recommendedthat the use of these procedures be further scrutinized todetermine their efficacy.SPRINT test performance was most repeatable overall (CV

,2%), with values closely corresponding to the results of pre-vious investigations (1.2% (12); 2.0% (29)). Within verticaljump test comparisons, the lowest intrasession and interses-sion CVs were associated with CMJ- (mean CV = 3.0%) andSJ-derived (3.5%) variables, with DJ (4.8%) variables typicallyless repeatable (Figure 2). These results are again in generalagreement with the CV values reported previously for CMJ(15,24,38,39), SJ (16,23,24), and DJ tests (16).To our knowledge, only Cronin et al. (16) have reported

CMJ, SJ, and DJ test repeatability in the same group of sub-jects observing similarly that DJ performance was the leastrepeatable (mean CV: DJ, 6.7%; SJ, 5.8%; CMJ, 3.6%). Here,the technical complexity of a DJ, coupled with inexperiencedsubjects, may have contributed to this larger variability. Dropjump performance is markedly influenced by the techniqueadopted, with a number of DJ variants recognized (e.g.,countermovement drop jump, bounce drop jump) (10).Moreover, participants were team-sport athletes and solikely less familiar with the DJ than the CMJ, which is animportant feature of team-sport performance (32). In con-trast to CMJ and SJ, our DJ test configuration used a forceplatform only, and so required participants to stand next tothe force plate before the DJ, rather than on it. The decisionto omit position transducer data from DJ test analysis wasmade after the observation during pilot testing that horizon-tal displacement could skew obtained position transducerdata. Drop jump performance was thus inferred throughreverse data integration, whereas displacement was indi-rectly measured; and so, further measurement error mayhave been introduced through additional calculations (25).Fatiguing protocol of this investigation was developed to

induce a similar form and degree of fatigue as elicited bytypical team-sport activities (8,22). Fatigue effects associatedwith both soccer and rugby league matches have been attrib-uted to muscle damage, muscle glycogen depletion, andincreased perception of effort (32,40). Although indicativeof both central and peripheral fatigue mechanisms, thesedescriptors provide little insight into how such changesmay influence neuromuscular function, both immediatelyand during the subsequent recovery phase.

Large widespread decreases in neuromuscular functionwere apparent immediately postexercise (Figure 3). Thesechanges appear unlikely related to limitations in energy sup-ply, as substrate depletion is not typically considered to con-strain Yo-Yo test performance (22), whereas recovery duration(e.g., 6 minutes after repeated sprints (26)) and test demands(i.e., test duration ,3 seconds; maximal phosphocreatine[PCr] breakdown rates: ;11% per second (9)) also unlikelyimpacted PCr stores. Other intramuscular perturbations maynevertheless have contributed (e.g., muscle pH (26), reactiveoxygen species (36)). These disruptions typically require;60 minutes for restoration (3) and so may have impairedneuromuscular propagation and excitation-contraction (E-C)coupling (1). Alternatively, structural (i.e., muscle damage andE-C coupling failure (14)), and neural (e.g., group III/IVaffer-ent activation and modified musculotendinous stiffness (5))changes are thought to contribute to neuromuscular fatigueresulting from stretch-shortening cycle (SSC) exercise (SSCfatigue) (33). Supraspinal changes (e.g., decreased centraldrive) are another possible contributory factor decreasing vol-untary drive to the muscle (1).Decreased sprint ability following fatiguing running-based

protocols is a common observation (4,20,30). Here, SPRINTperformance exhibited the most pronounced immediatepostexercise changes (mean ES = 3.7) but was restored by24-hour (Figure 3). A quicker restoration of sprint capacity(5-hour) compared with jump performance (.69 hours) hasbeen reported previously (4). Recovery of sprint abilitytherefore appears relatively quick; in which case, other fac-tors may limit athlete performance in a fatigued state (e.g.,technique, desire for maximal exertion).In contrast to the majority of other neuromuscular

variables, SJ peak force and time to peak force and powerwere substantially increased at 0-hour (Figure 3). Previousinvestigations have observed an unchanged SJ peak force(35) or significant decreases in SJ jump height (13) immedi-ately after simulated-soccer and muscle damaging exercise,respectively. Our disparate findings appear to relateto biomechanical SJ modifications. Participants were in-structed to squat deeply and consistently; however, thedecreased minimum displacement at this time point suggeststhat participants adopted a higher jump start position. Thismodification appears therefore to have enabled peak forceand power to be attained sooner, whereas the altered move-ment may also have affected how jump power was produced(i.e., increased force production at the expense of movementvelocity; indicated in the decreased PV and PP; Figure 3).Smaller effect sizes were displayed by most test variables

at 24-hour (Figure 3), possibly reflecting restoration of tran-sient fatiguing factors (e.g., intracellular milieu, central drive).SPRINT and SJ performance seemingly recovered com-pletely after this time point, whereas CMJ and DJ appearedto exhibit secondary decreases at 72-hour. These differenttrends could relate to the importance of eccentric functionand the SSC in each movement. The SSC is key to both




CMJ and DJ performance; however, the SJ does not use anSSC, whereas at shorter sprint durations (i.e., 20-m), accel-eration predominates which is largely determined by con-centric function (27). Consequently, assessment of eccentricfunction, or a neuromuscular function test comprising ofa considerable eccentric component, may be important forneuromuscular fatigue detection during the latter stages ofpostexercise recovery (i.e., ;72-hour).Countermovement jump and DJ performance displayed

similar fatigue time courses throughout postfatigue testing;widespread and pronounced decreases at 0-hour, a generalreturn to baseline at 24-hour, followed by a secondarydecrease at 72-hour. These responses mirror the biphasicrecovery profile of SSC fatigue, as previously demonstrated(17,33). The causes of this biphasic trend are speculated torelate to neural and mechanical responses resulting frommuscle damage and corresponding inflammatory and struc-tural remodeling processes (17). These processes arethought to activate group III/IV muscle afferents, resultingin altered stretch reflex responses (i.e., neural activation) anddecreased muscle stiffness (6,34). Anecdotally, the adoptionof back-to-back high-intensity/speed based trainingsessions (e.g., high neuromuscular load) followed bymultiple-day recovery may exploit such transient changes,maximizing training performance while minimizing theimpact on subsequent recovery.Neuromuscular fatigue responses may manifest as altered

neuromuscular strategies serving to limit performance dete-rioration (17,33). Our CMJ analysis included a number ofvariables that reflect how the jump was performed (e.g.,time- and rate-based variables). The changes at 72-hourappear to describe a modification of movement strategy withthe CMJ taking longer to perform (e.g., eccentric, concentric,and total duration, time to peak force/power, FT:CT) anda reduced eccentric component (e.g., F@0V) (Figure 3), aswe have discussed more thoroughly previously (18). Thus, inaddition to examining movement outcomes (e.g., jumpheight) and output (e.g., peak power/force), neuromuscularfatigue detection may be enhanced through additional con-sideration of how the movement is performed.Despite reduced CMJ and DJ performance, it is interesting

that SPRINT performance was improved at 72-hour(Figure 3). Although this may illustrate the absence of neu-romuscular fatigue, it could also relate to the predominantlyconcentric demands of sprint acceleration (27), or the lowersprinting demands during each push-off phase comparedwith jumping (e.g., sprint push-off force: 608 N per leg (20)vs. CMJ peak force: 2061 N, in this investigation), with thesedemands possibly insufficient to reveal neuromuscular defi-cits. Disagreement between vertical jump and sprint perfor-mance is not uncommon. Decreased CMJ, SJ, and DJperformance was observed following a soccer-simulationprotocol despite the maintenance of sprint performance(35), whereas sprint capacity has been found to require muchless time for restoration compared with CMJ performance

(5 vs. . 69 hours) (4). Corresponding with our observationsof modified CMJ mechanics, altered sprint mechanics (i.e.,decreased stride rate and increased stride length) are consid-ered a neuromuscular fatigue response, which may not nec-essarily elicit corresponding performance decreases (i.e.,sprint time) (20). Consequently, assessment of sprint capacityusing time-based variables alone may lack the requisite sen-sitivity to determine neuromuscular fatigue status during laterphases of postexercise recovery (i.e., .0-hour).Neuromuscular fatigue is highly task dependent, with

contributory mechanisms determined by numerous factorssuch as the athlete age, genetics, and training status (11).Therefore, the specifics of this study (e.g., the fatiguing pro-tocol used, athlete training status) likely contributed to theobserved results. Nevertheless, our findings suggest thatSSC-inclusive jump tests (e.g., CMJ and DJ) are most sensi-tive to neuromuscular fatigue, particularly during the laterrecovery phase (i.e., .0-hour, after initial postexercisefatigue). These observations are in contrast to previous re-ports suggesting that non-SSC jumps (i.e., SJ) were better forneuromuscular fatigue detection at similar postexercise timepoints (13). These investigations indicated that modificationsof eccentric function limited the extent of concentric perfor-mance deterioration. Although attempts to maintain con-centric performance may occur at the expense of eccentricfunction, our results highlight that measurement of eccentriccapacity and movement strategy can also reveal fatigue-induced neuromuscular manipulations. Our findings under-line the value in performing a comprehensive assessment ofneuromuscular function, which may in turn limit the value oftime-focussed sprint measurement for neuromuscular fatigueanalysis.The specificity of a test to the task performed is

fundamental to the capacity of test to detect neuromuscularfatigue (33), thus the seemingly greater fatigue sensitivity ofSSC-inclusive jumps may relate to the high eccentric load ofthe fatiguing protocol used (e.g., prolonged running). Like-wise, the value of SJ testing for neuromuscular fatigue assess-ment may be limited by the absence of an SSC. Finally,although CMJ and DJ tests appear to provide similar neuro-muscular fatigue sensitivity, the lower repeatability associ-ated with DJ performance, as well as the greater ecologicalvalidity of the CMJ, indicates that CMJ test is likely the mostsuitable tool for the monitoring of fatigue-induced neuro-muscular changes.In summary, the high repeatability and fatigue sensitivity

of the CMJ test indicated it to be the most valid test forneuromuscular fatigue detection in this investigation. Incomparison with both SPRINT and SJ testing, it appearedto offer enhanced capacity to detect neuromuscularchanges occurring in the later phases of postexerciserecovery (e.g., .24 hours) while also providing sufficientsensitivity in the early postexercise phase. Moreover, com-pared with DJ testing, CMJ performance was associatedwith superior repeatability.


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PRACTICAL APPLICATIONS

Neuromuscular function tests are an important aspect ofathlete fatigue monitoring; however, the most suitable testfor neuromuscular fatigue measurement for different sportsand athletes remains unclear. Results of this investigationunderline that different neuromuscular function tests vary intheir capacity to detect postexercise neuromuscular changes.Practitioners should therefore determine the usefulness(validity and sensitivity) of a neuromuscular test in thespecific circumstances in which it is to be used (e.g., athletefitness status, training status, the sport-specific fatiguingactivity). Although each test offered acceptable repeatabilityand displayed marked immediate postexercise decreases,large differences between tests were evident in the capacityto detect neuromuscular decrements during prolongedrecovery (i.e., from 0- to 72-hour postexercise). The impor-tance of the SSC inherent to each neuromuscular testappeared to contribute to these temporal differences, withperformance in tests relying more so on the SSC (i.e., CMJ,DJ) demonstrating greater sensitivity subsequent to 0-hourpostexercise than those relying less so (i.e., SJ, SPRINT).Neuromuscular tests that incorporate a considerable eccen-tric component may therefore provide superior sensitivity toneuromuscular fatigue after fatiguing lower-body SSC-basedexercise. Accordingly, to accurately discern athlete fatiguestatus and subsequent performance, practitioners shouldselect their neuromuscular test with knowledge as to whatstage during the training-recovery-adaptation cycle thata test will be used and the nature of fatigue experienced.

REFERENCES

1. Abbiss, CR and Laursen, PB. Models to explain fatigue duringprolonged endurance cycling. Sports Med 35: 865898, 2005.

2. Abernethy, P, Wilson, G, and Logan, P. Strength and powerassessment. Issues, controversies and challenges. Sports Med 19: 401417, 1995.

3. Allen, DG, Lamb, GD, and Westerblad, H. Skeletal muscle fatigue:Cellular mechanisms. Physiol Rev 88: 287332, 2008.

4. Andersson, H, Raastad, T, Nilsson, J, Paulsen, G, Garthe, I, andKadi, IF. Neuromuscular fatigue and recovery in elite femalesoccer: Effects of active recovery.Med Sci Sports Exerc 40: 372380,2008.

5. Avela, J and Komi, PV. Interaction between muscle stiffness andstretch reflex sensitivity after long-term stretch-shortening cycleexercise. Muscle Nerve 21: 12241227, 1998.

6. Avela, J, Kyrolainen, H, Komi, PV, and Rama, D. Reduced reflexsensitivity persists several days after long-lasting stretch-shorteningcycle exercise. J Appl Physiol 86: 12921300, 1999.

7. Bangsbo, J. Fitness Training in Football: A Scientific Approach. Bagsvaerd,Denmark: August Krogh Inst., University of Copenhagen, 1994.

8. Bangsbo, J, Iaia, FM, and Krustrup, P. The yo-yo intermittentrecovery test: A useful tool for evaluation of physical performance inintermittent sports. Sports Med 38: 3751, 2008.

9. Bishop, PA, Jones, E, and Woods, AK. Recovery from training: Abrief review: Brief review. J Strength Cond Res 22: 10151024,2008.

10. Bobbert, MF. Drop jumping as a training method for jumpingability. Sports Med 9: 722, 1990.

11. Borresen, J and Lambert, MI. The quantification of training load, thetraining response and the effect on performance. Sports Med 39: 779795, 2009.

12. Bradshaw, EJ, Maulder, PS, and Keogh, JW. Biological movementvariability during the sprint start: Performance enhancement orhindrance? Sports Biomech 6: 246260, 2007.

13. Byrne, C and Eston, R. The effect of exercise-induced muscledamage on isometric and dynamic knee extensor strength andvertical jump performance. J Sports Sci 20: 417425, 2002.

14. Byrne, C, Twist, C, and Eston, R. Neuromuscular function afterexercise-induced muscle damage: Theoretical and appliedimplications. Sports Med 34: 4969, 2004.

15. Cormack, SJ, Newton, RU, McGuigan, MR, and Doyle, TL.Reliability of measures obtained during single and repeatedcountermovement jumps. Int J Sports Physiol Perform 3: 131, 2008.

16. Cronin, JB, Hing, RD, and McNair, PJ. Reliability and validity ofa linear position transducer for measuring jump performance.J Strength Cond Res 18: 590593, 2004.

17. Dousset, E, Avela, J, Ishikawa, M, Kallio, J, Kuitunen, S,Kyrolainen, H, Linnamo, V, and Komi, PV. Bimodal recovery patternin human skeletal muscle induced by exhaustive stretch-shorteningcycle exercise. Med Sci Sports Exerc 39: 453460, 2007.

18. Gathercole, R, Sporer, B, Stellingwerff, T, and Sleivert, G.Alternative countermovement jump analysis to quantify acuteneuromuscular fatigue. Int J Sports Physiol Perform 10: 8492, 2014.

19. Gathercole, R, Stellingwerff, T, and Sporer, B. Effect of acutefatigue and training adaptation on countermovement jumpperformance in elite snowboard cross athletes. J Strength CondRes 29: 3746, 2014.

20. Girard, O, Micallef, JP, and Millet, GP. Changes in spring-massmodel characteristics during repeated running sprints. Eur J ApplPhysiol 111: 125134, 2011.

21. Hopkins, WG, Marshall, SW, Batterham, AM, and Hanin, J.Progressive statistics for studies in sports medicine and exercisescience. Med Sci Sports Exerc 41: 313, 2009.

22. Krustrup, P, Mohr, M, Amstrup, T, Rysgaard, T, Johansen, J,Steensberg, A, Pedersen, PK, and Bangsbo, J. The yo-yo intermittentrecovery test: Physiological response, reliability, and validity. MedSci Sports Exerc 35: 697705, 2003.

23. McGuigan, MR, Doyle, TL, Newton, M, Edwards, DJ, Nimphius, S,and Newton, RU. Eccentric utilization ratio: Effect of sport andphase of training. J Strength Cond Res 20: 992995, 2006.

24. McLellan, CP, Lovell, DI, and Gass, GC. The role of rate of forcedevelopment on vertical jump performance. J Strength Cond Res 25:379385, 2011.

25. McMaster, DT, Gill, N, Cronin, J, and McGuigan, M. A brief reviewof strength and ballistic assessment methodologies in sport. SportsMed 44: 603623, 2014.

26. Mendez-Villanueva, A, Edge, J, Suriano, R, Hamer, P, and Bishop, D.The recovery of repeated-sprint exercise is associated with PCrresynthesis, while muscle pH and EMG amplitude remaindepressed. PLoS One 7: e51977, 2012.

27. Mero, A. Force-time characteristics and running velocity of malesprinters during the acceleration phase of sprinting. Res Q Exerc Sport59: 9498, 1988.

28. Meylan, C, Cronin, J, and Nosaka, K. Isoinertial assessment ofeccentric muscular strength. Strength Cond J 30: 5664, 2008.

29. Moir, G, Button, C, Glaister, M, and Stone, MH. Influence offamiliarization on the reliability of vertical jump and accelerationsprinting performance in physically active men. J Strength Cond Res18: 276280, 2004.

30. Morin, JB, Tomazin, K, Samozino, P, Edouard, P, and Millet, GY.High-intensity sprint fatigue does not alter constant-submaximalvelocity running mechanics and spring-mass behavior. Eur J ApplPhysiol 112: 14191428, 2012.




31. Murphy, AJ andWilson, GJ. The ability of tests of muscular functionto reflect training-induced changes in performance. J Sports Sci 15:191200, 1997.

32. Nedelec, M, McCall, A, Carling, C, Legall, F, Berthoin, S, andDupont, G. Recovery in soccer: Part IPost-match fatigue and timecourse of recovery. Sports Med 42: 9971015, 2012.

33. Nicol, C, Avela, J, and Komi, PV. The stretch-shortening cycle: Amodel to study naturally occurring neuromuscular fatigue. SportsMed 36: 977999, 2006.

34. Nicol, C, Kuitunen, S, Kyrolainen, H, Avela, J, and Komi, P. Effects oflong- and short-term fatiguing stretch-shortening cycle exercises onreflex EMG and force of the tendon-muscle complex. Eur J ApplPhysiol 90: 470479, 2003.

35. Oliver, J, Armstrong, N, and Williams, C. Changes in jumpperformance and muscle activity following soccer-specific exercise.J Sports Sci 26: 141148, 2008.

36. Perrey, S, Racinais, S, Saimouaa, K, and Girard, O. Neural andmuscular adjustments following repeated running sprints. Eur J ApplPhysiol 109: 10271036, 2010.

37. Reilly, T, Morris, T, and Whyte, G. The specificity of trainingprescription and physiological assessment: A review. J Sports Sci 27:575589, 2009.

38. Sheppard, JM, Cormack, S, Taylor, KL, McGuigan, MR, andNewton, RU. Assessing the force-velocity characteristics of the legextensors in well-trained athletes: The incremental load powerprofile. J Strength Cond Res 22: 13201326, 2008.

39. Taylor, KL, Cronin, J, Gill, ND, Chapman, DW, and Sheppard, J.Sources of variability in iso-inertial jump assessments. Int J SportsPhysiol Perform 5: 546558, 2010.

40. Twist, C and Highton, J. Monitoring fatigue and recoveryin rugby league players. Int J Sports Physiol Perform 8: 467474,2013.


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comparação de diferentes testes de campo

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