Horizontal and vertical jump.pdf

7/21/2019 Horizontal and vertical jump.pdf

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Original research

Horizontal and vertical jump assessment: reliability, symmetry,discriminative and predictive ability

Peter Maulder*, John Cronin

New Zealand Institute of Sport and Recreation Research, Auckland University of Technology, Private Bag 92006, Auckland 1020, New Zealand

Received 26 July 2004; revised 4 January 2005; accepted 17 January 2005

Abstract

Objectives: The purpose of this study was to: (1) establish the reliability of a new unilateral concentric only horizontal jump assessment(HSJ) then compare the reliability of this test to other types of unilateral vertical and horizontal jumps; (2) compare the tests to whether they

differ in their ability to determine limb asymmetries; and (3) investigate the relationship between these jumps and sprint running.

Methods: Eighteen sportsmen performed unilateral jump assessments involving the horizontal squat jump, horizontal countermovement

jump, horizontal repetitive jump, vertical squat jump, vertical countermovement jump, and vertical repetitive jump.

Results: Reliability for the new test was found to be the equal if not better than the other more established tests of leg power, with the

within trial variation (CVZ1.11.9%) and testretest reliability (ICCZ0.890.90). None of the tests were found to have greater

discriminative ability in determining limb asymmetries. Stretch shorten cycle enhancement was greater in the vertical tests (12.1%)

compared to the horizontal tests (1.3%). Horizontal jump assessments (rZK0.73 to K0.86) were found better predictors of 20-m sprint

performance than the vertical assessments (rZK0.52 toK0.73), with the horizontal cyclic assessment being the best predictor (rZK0.86).

Conclusion: Horizontal leg power assessment appears an inexpensive, easy to administer, reliable and valid method to assess unilateral

leg power.

q 2005 Published by Elsevier Ltd.

Keywords: SSC; Concentric only; Sprint performance; Acyclic; Cyclic

1. Introduction

Human movement is made possible by force development

in muscles acting across the levers of the skeletal system. The

force or torque a muscle or muscle group can generate is

referred to as strength whereas power has been defined as the

rate of performing work or the product of force and velocity

(Komi, 1992; Sale, 1991). The application of strength and

power usually occur under conditions delimited by posture,contraction type and movement pattern (Harman, 1993;

Komi, 1992; Sale, 1991). Such a definition implies that

strength or power has many manifestations, is very specific

and should be measured within a functional context. In terms

of measuring functional power of the lower body the single

hop for distance (Bandy, Rusche, & Tekulve, 1994; Barber

et al., 1990; Bolgla & Keskula, 1997; Clark, Gumbrell, Rana,

Traole, & Morrissey, 2002; Paterno & Greenberger, 1996),

triple hop for distance (Bandy et al., 1994; Bolgla & Keskula,

1997; Clark et al., 2002; Risberg, Holm, & Ekeland, 1995),

6-m timed hop (Barber et al., 1990; Bolgla & Keskula, 1997;

Clarket al., 2002; Hopper et al., 2002), crossover hop (Bandy

et al., 1994; Bolgla & Keskula, 1997; Clark et al., 2002;

Hopper et al., 2002), single leg vertical jump (Bandy et al.,1994; Barber et al., 1990; Cordova & Armstrong, 1996;

Hopper et al., 2002; Risberg et al., 1995), vertical squat jump

(Arteaga, Dorado, Chavarren, & Calbet, 2000; Cornwell,

Nelson, Heise, & Sidaway, 2001; Cornwell, Nelson, &

Sidaway, 2002; Knudson, Bennett, Corn, Leick, & Smith,

2001; Young, 1995; Young & Elliot, 2001), vertical

countermovement jump (Arteaga et al., 2000; Cornwell

et al., 2001, 2002; Hunter & Marshall, 2002; Knudson et al.,

2001; Young, 1995), and the drop jump(Arteaga et al., 2000;

Physical Therapy in Sport 6 (2005) 7482

www.elsevier.com/locate/yptsp

1466-853X/$ - see front matter q 2005 Published by Elsevier Ltd.

doi:10.1016/j.ptsp.2005.01.001

* Corresponding author. Tel.: C64 9 917 9999x7119; fax: C64 9 917

9960.

E-mail address:[email protected] (P. Maulder).
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Golomer & Fery, 2002; Hunter & Marshall, 2002; Young,

1995; Young & Elliot, 2001) seem the assessment methods

most widely used. Other jump assessments that have been

used to measure lower body power include the stair hop

(Hopper et al., 2002), adapted crossover hop (Clark et al.,

2002), side hop (Itoh, Kurosaka, Yoshiya, Ichihashi, &

Mizuno, 1998) and repeated vertical jumps (Tkac, Hamar,Komadel, & Kuthanova, 1990).

It would seem that a variety of jumps are available to

measure leg power, the issue would seem, therefore, which

jump/s may be of better prognostic or diagnostic value to the

clinician or conditioner. Obviously issues of validity and

reliability need to be addressed and should guide jump

assessment selection. The use of unilateral assessment

appears to have an advantage over bilateral assessment, as

differences in limb symmetry can be identified and also

measurements of the non-injured limb can serve as the

biological baseline to which the injured limb should return

(Hopper et al., 2002). Also in terms of specificity many

activities require unilateral propulsion either in the vertical

or horizontal directions, therefore, unilateral assessment

would appear to better represent the power specific to these

movement patterns. Given this information it is puzzling

why the majority of research uses bilateral jump assessment

as the representative measure of leg power.

Another issue determining selection may be that most

activities require cyclic expressions of force, therefore, the

use of multiple jumps would intuitively make sense.

However, much of the jump assessment reported in the

literature is acyclic in nature (Barber et al., 1990; Cornwell

et al., 2001, 2002; Hopper et al., 2002; Itoh et al., 1998;

Mero, Luhtanen, & Komi, 1983; Young, 1995; Young &Elliot, 2001). Also, most functional activities are the result

of a combination of horizontal, mediolateral and/or vertical

ground reaction forces. Matching the type of jump in terms

of movement pattern would seem fundamental to selection.

The predilection in the literature to use the vertical jump as

the preferred method of power assessment seems question-

able in this context.

The preoccupation of research to use the derivatives

of the vertical jump as measures of leg power, may be

attributed to the notion that more information can be

gained from this type of assessment. For example, some

vertical jumps are thought to measure different strength

qualities. The squat jump (SJ) has been described as a

measure of leg explosiveness under concentric only

conditions. Whereas the countermovement jump (CMJ)

assessed leg power under slow-stretch shorten cycle

(SSC) and low stretch load conditions. The drop jump is

thought to be a measure of fast SSC behaviour and the

stretch load tolerance of the musculotendinous unit

(Young, 1995). Having jump assessments that not only

give a global sense of function but also have the ability

to differentiate between different types of muscle

function (concentric or slow and fast SSC behaviour),

would be of greater prognostic and diagnostic value to

health professionals by assisting to better shape rehabi-

litation and conditioning interventions. Whether vertical

jumps do this to better effect than horizontal jumps

though needs investigation.

There is a paucity of published research into the

relationship of strength and power measures to functional

performance. Abernethy, Wilson, and Lopgan (1995)believed this to be reflective of the low priority given to

publishing research of this nature by editors and researchers.

However, it is argued that such research is important as it

allows predictors of functional performance to be identified,

which aid talent identification, diagnosis, prognosis,

program development and may provide direction for

mechanistic research. Research that has investigated the

relationship between leg power and functional performance

(e.g. running and sprinting) has mostly used bilateral

vertical jumps and their derivatives as the assessment

method of choice (Golomer & Fery, 2002; Mero et al., 1983;

Nesser, Latin, Berg, & Prentice, 1996; Young, 1995). Theuse of bilateral vertical assessment to predict these activities

is puzzling. Intuitively it would seem that horizontal jump

assessment, which involves both vertical and horizontal

propulsive forces, would better predict those activities that

involve horizontal linear motion. However, very few studies

(Nesser et al., 1996) have used horizontal jump assessment

to determine relationships with functional performance of a

horizontal nature. Once more, the prevalence in the research

is to use acyclic type movements (e.g. squat, counter-

movement jumps, vertical jumps and drop jumps) to predict

cyclic activities. This may in turn explain why only

moderate relationships (rZK0.46 to K0.77) are reported

between acyclic (vertical jumps) and cyclic (sprinting) tasks

(Kukolj, Ropret, Ugarkovic, & Jaric, 1999; Nesser et al.,

1996; Young, 1995).

Given all this information, the question of interest is why

the predilection of research to use acyclic vertical jump

assessments to measure leg power. Is it that bilateral vertical

jump assessments are easier to administer and more reliable

than horizontal jump techniques? Do they have greater

prognostic/diagnostic value than the horizontal jump

assessments? Is it that the vertical jumps can delineate

between concentric and SSC function whereas there is no

test known to these authors of horizontal concentric only

function? Or is it simply that the vertical jumps do predictperformance such as walking and running to better effect

than horizontal type jumps? Answering these questions

provides the purpose for this study. First, the reliability of a

new unilateral concentric only horizontal jump assessment

will be established and the reliability of this test compared

to other types of unilateral vertical and horizontal jumps.

Second, the tests are compared to whether they differ in their

ability to determine imbalances between limbs. Third, the

relationship between these jump tests and sprint running is

investigated to determine if any of the tests are better

predictors of functional performance.

P. Maulder, J. Cronin / Physical Therapy in Sport 6 (2005) 7482 75


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2. Methods

2.1. Subjects

Eighteen male subjects volunteered to participate in this

research. The subjects were involved in a wide variety of

sports that predominantly involved the lower body. Theirage, mass and height were 25.1G4.3 years, 78.8G9.3 kg

and 176.8G5.1 cm, respectively (meanGSD). All subjects

signed an informed consent form prior to participation in

this research. The Human Subject Ethics Committee,

Auckland University of Technology, approved all the

procedures undertaken.

2.2. Equipment

2.2.1. Contact mat system

Thecontact matsystem(Swift Performance,University of

Southern Cross, Australia) consists of a portable battery-

powered computer unit, a connecting cable anda contactmat,

and was used to measure vertical single leg jump perform-

ance. The system measures jump height (cm), flight time

(ms) and ground contact time (ms). Reliability between the

contact mat system and a force platform (AMTI Force Plate

and Amplifier; Advanced Technology, Inc., Washington,

USA) revealed no significant differences between the contact

mat system and force platform for flight (intraclass

correlation coefficientZ0.95; P!0.001) or contact times

(intraclass correlation coefficientZ0.99;P!0.001).

2.2.2. Timing light system

The timing light system was a dual-beam modulatedvisible red-light system with polarizing filters (Swift

Performance, University of Southern Cross, Australia).

This system was used to measure sprint performance.

2.3. Testing procedures

Testing was performed within one session, however, 10

subjects returned to repeat the jump assessments in a second

session, in order to determine the reliability of the test

procedures. Prior to data collection, the subjects age, height

and mass were recorded. Additionally subjects were asked

which leg was preferred for kicking a ball, with the

preferred leg being considered the dominant leg. Subjects

completed a standardised warm-up that consisted of 5 min

jogging at a self-selected pace followed by 3 min stretching

of muscles of the lower extremity of the subjects choice.

Each stretch was held for 20 s. Following the warm-up

participants performed three practice trials for each of the

jump assessments. After the practice trials, three test trials

were performed for each leg for each test in the following

order: vertical squat jump, vertical countermovement jump,

vertical repetitive (cyclic) jump, horizontal squat jump,

horizontal countermovement jump and horizontal repetitive

(cyclic) jump. During all jump assessments subjects were

instructed to keep their hands placed on their hips. Tests

were performed on both the left and right legs alternating

legs between trials. A rest period of 30 s was given between

practice and test trials on the same leg. Following the jump

assessments the sprint assessments were performed. Sub-

jects were allowed two practice trials followed by three test

trials. A rest period of up to 3 min was given betweenpractice and test sprints. Establishing reliability of these

procedures involved testing on two separate days with at

least 2 days but no more than 7 days separating the two

sessions. Testing took place at approximately the same time

of day in the same room at the same temperature.

2.4. Jump assessments

2.4.1. Vertical squat jump (VSJ)

The subject started with the foot of the designated testing

leg on the contact mat and their hands on their hips, they

were then instructed to sink and hold a knee position

(approximately 1208knee angle), and the experimenter then

counted out 4 s. On the count of four the subject was

instructed to then jump as high as possible. A successful

trial was one where there was no sinking or counter-

movement prior to the execution of the jump. With all

vertical jumps, it was recommended that at take-off, the

subject leave the mat with the knees and ankles extended

and land in a similarly extended position (Young, 1995).

2.4.2. Vertical countermovement jump (VCMJ)



were then instructed to sink (approximately 1208

kneeangle) as quickly as possible and then jump as high as

possible in the ensuing concentric phase.

2.4.3. Vertical repetitive (cyclic) jump (VRJ)



were then instructed to sink (approximately 1208 knee

angle) as quickly as possible and then jump as high as

possible for three consecutive jumps. Instructions were to

jump for maximum height and to minimise their contact

times in between jumps.

2.4.4. Horizontal squat jump (HSJ)

A chair approximately 0.69 m high was placed against a

wall, this chair height was used as it was a suitable height in

which all subjects could be in a comfortable start position

for the assessment (seeFig. 1). The subject was in a position

on the chair so that their gluteal fold was resting on the edge

of the chair, and their hands on their hips. A start line was

then marked in front of the toe where the knee was at an

angle of 1208. The subjects trunk was in a position similar

to their vertical squat jump position. Subjects were then

instructed to jump as far forward as possible and land on two

feet. For all horizontal jumps, the experimenter measured

P. Maulder, J. Cronin / Physical Therapy in Sport 6 (2005) 748276


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the distance from the starting line to the subjects closest

heel.

2.4.5. Horizontal countermovement jump (HCMJ)

Subjects began by standing on the designated testing leg

with their toe in front of the starting line, and their hands on

their hips. Subjects were instructed to sink (approximately

1208knee angle) as quickly as possible and then jump as farforward as possible and land on two feet.

2.4.6. Horizontal repetitive (cyclic) jump (HRJ)

Subjects began by standing on the designated testing leg

with their toe in front of the starting line and hands on their

hips. Subjects were instructed to take three maximal jumps

forward as far as possible on the testing leg and land on two

legs of the final jump.

2.5. Sprint assessment

Timing lights were placed at the start and at a distance of20 m. The starting position was standardized for all

subjects. Athletes started in a two point crouched position

with their preferred foot 50 cm from the starting line and

their other foot in line with the heel of the preferred foot.

2.6. Data analysis

All vertical jump heights were determined by the flight

time from the contact mat according to the formula of

(Young, 1995)

Jump heightcmZgt2=8

where

gZacceleration due to gravity (9.81 m sK2).

tZflight time of the jump (s).

The symmetry index was determined by the procedures

described byBarber et al. (1990):

Nondomiant leg

Dominant leg !100

Vertical and horizontal reactive strength values were

determined using the following formula according to

Young (1995):

Countermovement jump CMJcmKSquat jump SJcm

Reactive strength percentage differences were calculated

using the following equation:

Difference%ZCMJKSJ

CMJ !100

2.7. Statistical analyses

Following data collection, means and standard deviations

were calculated for all results. The three trials for each leg of

each jump assessment and sprint times were averaged for an

individual subject mean, and subject means for each

assessment were averaged to provide a group mean. The

reliability of the jump assessment procedures was calculated

using two different statistical methods. A coefficient of

variation (CV) was calculated for all test variables to

determine the stability of measurement among trials (CVZ

SD/mean!100) of 10 subjects. Intraclass correlation coeffi-

cients were calculated to determine testretest reliability.

Paired T-tests were used to determine if any significant

differences existed between the dominant and non-dominant

legs. If no significant differences existed the data was then

averaged to make one data set for each jump assessment,

which was then used to determine relationships between

jump performance and sprint times using Pearson product

moment correlations. Significance was accepted atP! 0.05

for all statistical tests.

3. Results

It can be observed fromTable 1that there was less within

trial variation associated with the horizontal jumps (CVZ

1.12.0%) as compared to the vertical jumps (CVZ3.3

8.8%). In fact the new unilateral concentric only horizontal

jump test was most stable (CVZ1.1%) between trials. The

greatest variability between trials was found in the vertical

repetitive (cyclic) jump (CVZ8.8%). Less variability was

observed for the dominant leg compared to the non-

dominant for all jump assessments excluding the horizontal

triple jump (seeTable 1). In terms of testretest reliability

the horizontal tests (ICCZ0.800.97) appeared more

reliable than the vertical jump tests (ICCZ0.710.95).

Interestingly the highest and lowest intraclass correlation

coefficients were found for the horizontal (ICCZ0.97) and

vertical (ICCZ0.71) cyclic jump tests. Intraclass

correlation coefficients were also greater for the dominant

leg compared to the non-dominant for all jump assessments

excluding the horizontal triple jump (seeTable 1).

The mean values for both the dominant and non-dominant

limbs for all subjects are presented in Table 2. Mean

symmetry index scores were calculated, showing

very small deficits (99102) for all jump assessments.

Fig. 1. Horizontal squat jump.



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Greater inter-individual variability in limb symmetry was

noted in the vertical jump assessments (see standard

deviations). No significant differences between dominant

and non-dominant limbs were found for all jump assessments

(seeTable 2).

A greater number of subjects were found to have

imbalances between the dominant and non-dominant

limbs when the vertical jumps were used to determine

limb symmetry (seeTable 3). No subjects had greater than

15% difference in the jumps for distances (horizontal jumps)

whereas one to two subjects were found to have greater than

15% between limb differences for the jumps for height

(vertical jumps).

The difference between concentric only and SSC

performance in the vertical and horizontal acyclic jumps

can be observed fromTable 4. The SSC enhancement was

far greater (averageZ12.1%, rangeZ1.328.6%) for the

vertical jump assessment as compared to the horizontal

assessments (averageZ1.3%, rangeZK13.4 to 10.3%). It

should be noted that there was greater inter-individual

variability (SDZ8.8 cm) associated with the horizontal

jump assessment.

The relationships between the vertical and horizontal

jumps, and 20-m sprint performance can be observed

in Table 5. It can be noted that all horizontal jump

assessments were found to have stronger relationships

(rZK0.73 to K0.86) with sprint performance than the

vertical jump assessments (rZK0.52 to K0.73). The

horizontal repetitive jump had the highest correlation with

20-m sprint performance (rZK0.86) whereas the vertical

repetitive jump had the lowest (rZK0.52). The inter-

relationships between horizontal and vertical jump

Table 1

Mean and standard deviations (SD), coefficient of variation (CV) and intraclass correlation coefficients (ICC) for the jump assessment (10 subjects)

Variables MeanGSD CV% ICC

Horizontal squat jump

Distance (m) Dominant leg 1.607G0.155 1.1 0.90 (0.000)

Non-dominant leg 1.620G0.143 1.9 0.89 (0.000)

Horizontal countermovement jumpDistance (m) Dominant leg 1.659G0.158 1.9 0.95 (0.000)


Horizontal repetitive jump

Distance (m) Dominant leg 5.142G0.794 1.9 0.97 (0.000)


Vertical squat jump

Height (m) Dominant leg 0.157G0.040 3.3 0.86 (0.000)


Vertical countermovement jump

Height (m) Dominant leg 0.184G0.042 3.3 0.86 (0.000)


Vertical repetitive jump

Total height (m) Dominant leg 0.436G0.098 5.5 0.71 (0.007)


Table 2

Mean (SD), symmetry index and P-values of the dominant and non-dominant legs for the horizontal and vertical jumps of all subjects

Variables Dominant Non-dominant Symmetry index Pvalue

HSJ (m) 1.596G0.139 1.617G0.136 101G4 0.211

HCMJ (m) 1.642G0.147 1.624G0.177 99G6 0.407

HRJ (m) 5.105G0.740 5.116G0.657 101G5 0.862

VSJ (m) 0.164G0.039 0.162G0.032 100G11 0.664

VCMJ (m) 0.186G0.043 0.186G0.038 101G10 0.876

VRJ (m) 0.428G0.109 0.434G0.107 102G9 0.526

HSJ, horizontal squat jump; HCMJ, horizontal countermovement jump; HRJ, horizontal repetitive jump; VSJ, vertical squat jump; VCMJ, verticalcountermovement jump; VRJ, vertical repetitive jump.

Table 3

The number of subjects (%) exhibiting different levels of limb asymmetry

Limb sym-

metry (%)

HSJ

(m) (%)

HCMJ

(m) (%)

HRJ

(m) (%)

VSJ

(m) (%)

VCMJ

(m) (%)

VRJ

(m) (%)

O90 94.4 83.3 94.4 72.2 72.2 61.1

O85 100 100 100 88.9 94.4 94.4

!85 0 0 0 11.1 5.6 5.6

Limb symmetry values denote the common variance between limbs, i.e.

O90% means that the non-dominant leg was at least 90% of the dominant

leg in terms of the jump measure being assessed or vice versa.



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assessments mostly ranged between rZ0.66 and 0.76 with

the exception of two comparisons.

4. Discussion

4.1. Reliability

One aim of the research was to determine the reliabilityof a new unilateral concentric only horizontal jump

assessment and thereafter compare the reliability of this

test to other types of unilateral vertical and horizontal

jumps. In terms of the new test the within trial variation

(CVZ1.11.9%) and testretest reliability (ICCZ0.89

0.90) was found to be the equal if not better of other more

established tests of leg power. Interestingly the horizontal

tests were found to have greater stability within trials (CVZ

1.12.0%) and across testing occasions (ICCZ0.800.97)

than the vertical tests. Thus the original speculation that the

preoccupation of research to use vertical jump assessment

was based on greater reliability with this type of assessment

seems unfounded. Similar results have been reported in the

literature. For example, Risberg and co-workers (1995)

reported CV values of 2.0 and 2.4% for the non-dominant

and dominant legs, respectively, for the horizontal repetitive

jump. Arteaga and colleagues (2000) have reported CV

values of 5.4 and 6.3% for the vertical squat jump and

vertical countermovement jump, respectively, in their study

performed on active males and females, however, their jump

assessments were performed bilaterally. The ICCs found in

this study appear similar to those reported by Ross,

Langford, and Whelan (2002)for the horizontal repetitive

jump (ICCZ0.97), and Risberg et al. (1995) for the HRJ

(ICCZ0.92). ICCs of 0.920.96 have been reported by(Bandy et al., 1994; Bolgla & Keskula, 1997; Paterno &

Greenberger, 1996; Ross et al., 2002) for the horizontal

countermovement jump performed on the dominant leg,

which are also consistent with the findings of the present

study.

The jump assessment that showed the greatest variability

was the vertical repetitive jump (VRJ) performed on both

the dominant leg and non-dominant leg (CVZ

5.5 and 8.8%,respectively). A possible reason for the VRJ assessment

resulting in higher variability could be attributed to the

difficulty subjects had repeating three jumps whilst staying

on the mat. That is, there was substantial horizontal and

lateral displacement that occurred during the flight phase of

the jumps, which caused the subjects to land in a different

position on the contact mat, which may in turn have affected

jump height. Three practice trials were given for the VRJ

assessment, however, it may be possible that a longer

familiarisation period is required for less variability to

occur.

4.2. Limb symmetry

A secondary aim was to compare the jump assessments

as to whether they differ in their ability to determine

imbalances between limbs. The symmetry index calculated

for all jump assessments was found to show very little

difference between dominant and non-dominant legs in

healthy subjects with no previous history of lower limb

pathology. Also no significant differences were found

between legs using Paired t-tests. With respect to the

symmetry index scores it could be suggested that no one

jump assessment had the ability to determine limb

asymmetries more so than the other for individuals with

no history of lower limb pathology. Similar symmetry index

scores and differences have been reported in the literature.

For example, Barber and colleagues (1990) reported a

similar symmetry index (100G13) for the horizontal

countermovement jump when calculated for healthy sub-

jects. However,Itoh et al. (1998),found that healthy male

subjects were significantly different in horizontal counter-

movement jump performance between the dominant

(1.93G0.19 m) and non-dominant leg (1.84G0.18 m).

If the symmetry index scores are interpreted in terms of

the percent of subjects falling within certain bands of limb

asymmetry (see Table 3), a greater appreciation ofthe potential diagnostic value of the tests may be gained

Table 4

Differences in concentric and SSC performance (%) between vertical and

horizontal jumps

Variables Raw difference (cm)

(meanGSD)

Difference (%)

Horizontal SSC enhancement

HCMJ-HSJ 2.6G8.8 1.3

Vertical SSC enhancement

VCMJ-VSJ 2.3G1.8 12.1

Table 5

Intercorrelation matrix [r(Pvalue)] between jump assessments and sprint performance

Variables HSJ (m) HCMJ (m) HRJ (m) VSJ (m) VCMJ (m) VRJ (m) S 20 (s)

HSJ (m) 1.0

HCMJ (m) 0.83 (0.000) 1.0

HTJ (m) 0.83 (0.000) 0.93 (0.000) 1.0

VSJ (m) 0.66 (0.003) 0.71 (0.001) 0.76 (0.000) 1.0

VCMJ (m) 0.66 (0.003) 0.79 (0.000) 0.86 (0.000) 0.90 (0.000) 1.0

VTJ (m) 0.44 (0.067) 0.69 (0.002) 0.69 (0.002) 0.76 (0.000) 0.88 (0.000) 1.0

S 20 (s) K0.73 (0.001) K0.74 (0.000) K0.86 (0.000) K0.56 (0.015) K0.73 (0.001) K0.52 (0.026) 1.0



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(Barber et al., 1990; Risberg et al., 1995). It would seem that

the vertical jump measures might be more sensitive to limb

asymmetry than the horizontal tests. That is, a larger

percentage of the population were found to have limb

asymmetries greater than 90%. However, it may also

indicate that limb symmetry is movement specific and that

limb asymmetries may exist in the vertical and not in themediolateral or anterioposterior directions. More research is

needed to establish the merits of such a contention.

However, until this occurs the clinician/conditioner needs

to be cognizant of these findings and their implications.

4.3. SSC enhancementreactive strength

The augmentation of concentric muscle action from a

pre-stretch is typically attributed to: the storage and

re-utilisation of elastic energy stored in the series

elastic component (SEC) of the musculotendinous system

(Asmussen & Bonde-Petersen, 1974; Komi & Bosco, 1978);

spinal reflexes (Dietz & Schmidtbleicher, 1981) as well as

long latency responses (Melvill-Jones & Watt, 1971) that

increase muscle stimulation, allowing the muscle to reach

maximum activation before the onset of the concentric

muscle action (van Ingen Schenau, 1984) It can be

calculated as CMJKsquat jump or as a percentage

[(CMJKSJ/CMJ)!100]. The SSC enhancement for the

vertical jumps of this study was 2.3 cm or 12.1% and is

consistent to those reported previously (2.5 cm) (Young,

1995) and similar to the pre-stretch augmentation (1020%)

found by Asmussen and Bonde-Petersen (1974). Interest-

ingly this pre-stretch augmentation was much less in the

horizontal plane. That is, the difference between thehorizontal squat and countermovement jumps was 1.3%. It

would seem that the vertical loading of the musculotendi-

nous unit provides a greater stretch-load (SSC) stimulus

than that provided by the horizontal jump. As a result

greater elastic energy is stored and utilised in the ensuing

concentric contraction. If so, this has interesting impli-

cations for the training of reactive or SSC type motion

Furthermore, the findings would also suggest that the

vertical jump assessments would be best used if an

individuals SSC ability was being assessed.

4.4. Relationships between jump and sprint performance

The final aim of the study was to investigate the

relationship between the jump tests and sprint running,

then determine if any of the jump tests were better

predictors of sprint performance. Significant correlations

were found between all jump assessments and sprint

performance. Previous studies (Golomer & Fery, 2002;

Kukolj et al., 1999; Mero et al., 1983; Nesser et al.,

1996; Young, 1995) have reported significant correlations

(rZK0.46 to K0.81) between sprint performance

measures and various jump assessments. An interesting

finding from this study was that the horizontal jump

assessments (rZK0.73 to K0.86) were found to have

stronger relationships with sprint performance than all

the vertical jump (rZK0.52 to K0.73) assessments (see

Table 5). It seems that the horizontal jump assessments are

better predictors of sprint performance than vertical jump

assessments. It is not surprising that the horizontal

assessments had the stronger relationships as sprinting ismade up of a strong horizontal component, which the

vertical jumps fail to assess. What is of further interest is the

finding that the horizontal cyclic jump was the best predictor

of sprint performance (rZK0.86), which begs the question

as to why use assessments that are vertical and/or acyclic in

nature to predict sprint performance?

The findings of this study are similar to those reported

previously. Mero and co-workers (1983) for example,

reported significant correlations between the vertical squat

jump (rZ0.65) and vertical countermovement jump (rZ

0.70) and the acceleration phase (10 m) velocity of male

sprinters. Similarly,Young and colleagues (1995)reported a

significant correlation between sprint performance (fastest

10 m segment) and VCMJ (rZK0.77), which is similar

to the correlation found between VCMJ and 20-m

sprint performance (rZK0.73) in this study. Nesser and

colleagues (1996)using a five-step horizontal jump reported

a strong relationship (rZK0.81) with 40-m sprint perform-

ance, which is consistent with the findings of the present

study. During the five-step jump rapid stretching and high

velocity contractions of the lower extremity occur (Nesser

et al., 1996), which is very similar to that which occurs

during sprinting. However, Mero and co-workers (1983)

reported a low relationship (rZ0.66) between the HRJ and

acceleration phase (10 m) velocity. This difference couldmost probably be attributed to the contention that the

beginning phases of a sprint are predominantly concentric or

slow SSC in nature. Therefore, a test such as the repetitive

horizontal jump may not be as specific to this phase as the

later maximum speed phase.

An interesting finding in the present study was the low to

moderate relationships observed between horizontal and

vertical jump assessments. One would assume that as both

the vertical and horizontal jump assessments are measuring

leg power, the common variance (R2) between tests would

be greater than 50%. The common variance between the

horizontal and vertical tests ranged between 19.3 and

73.9%, with the majority of tests sharing less than 50%

common variance. This would indicate that the vertical and

horizontal tests are measuring different leg power qualities

and should not be used interchangeably.

5. Conclusion

Presently the functional performance tests used for

rehabilitation or for performance assessment give a global

sense of function. For example, one limb is less powerful

(distance, height) than the other. Such information is of little



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diagnostic value. Having a battery of tests that not only give

a global sense of function but also have the ability to

differentiate between acyclic concentric, acyclic stretch

shorten cycle (SSC) and cyclic SSC function, would be of

greater prognostic and diagnostic value to the clinician and

conditioner alike. Concerns regarding reliability, validity,

expense, ease of administration and portability shoulddetermine selection of the test/s used to assess the functional

ability of an athlete. It should be realised that the results of

this study have been based on a relatively small sample of

athletes from a wide variety of sports. Whether these results

are similar to other populations needs further study.

Nonetheless, the results of this study indicate high stability

between trials and sessions for the majority of the single leg

jump assessments in particular the horizontal jump assess-

ments investigated in this study. The new horizontal squat

jump assessment was amongst the most reliable of

measures. If one leg is to be assessed it is suggested that

the dominant leg be used due to greater variability

associated with the non-dominant leg for most assessments.

In terms of determining limb asymmetry both horizontal and

vertical tests appear of similar discriminative ability.

Vertical assessments appear to have greater discriminative

ability than horizontal assessments for identifying the

contribution of muscle pre-stretch, when comparing a

jump of SSC nature to that of a concentric only jump

assessment. All horizontal jump assessments investigated in

this study were found to have stronger correlations with

sprint performance than the vertical jump assessments, the

cyclic horizontal repetitive jump was found to have the

highest correlation with sprint performance. For these

reasons the clinician, conditioner and or sports practitionershould feel reassured in the knowledge that horizontal jump

assessment can give reliable information similar if not better

to vertical jump assessment. It should be realized, however,

that no single strength/power measure or assessment

protocol can hope to explain all the variance associated

with a performance measure. The challenge therefore is to

develop assessment batteries that provide insights into the

determinants of functional performance.

Acknowledgements

This study was supported by the New Zealand Institute of

Sport & Recreation Research Summer Studentship through

the Auckland University of Technology.

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