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THE RELATIONSHIP BETWEEN ISOKINETIC HIP STRENGTB AND CLOSED KINETIC PERFORMANCE IN ELITE HOCKEY PLAYERS

A. Jason Kea School of Physical Therapy

Submitted in partial Mfilment of the requirements for the degree of

Master of Science

Faculty of Graduate Studies The University of Western Ontario

London, Ontario April, 1999

'A, Jason Kea 1999

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Abstract

The purposes of the study were to examine: 1) the test-retest reliability of isokinetic hip

abductor and adductor peak torques; 2) the test-retest reliability of one-legged hop tests in

the medial and lateral directions; and 3) the reeltiomhip between hip muscle strength and

the hop tests. The dominant leg of 27 elite male hockey players was tested on two

occasions, at least 72 hours apart. Isokinetic testing was performed on a computerized

dynamometer (Kin-Corn) at 60°fsec using concentric-abduction, eccentric-abduction,

concentric-adduction, and eccentric-adduction movements. The one-legged hops were

tested in the medial and lateral directions. The Intraclass Correlation Coefficients (KC)

for the isokinetic tests were modest for data collected on one test occasion (ICC 2,1=

0.59 to 0.74) and generally excellent for data averaged over two test occasions (KC 2 J =

0.74 to 0.85) suggesting that two test occasions are desirable to maximize reliability. The

ICCs for the lateral and medial hops were excellent (KC 2,1= 0.91 and 0.87) for one test

occasion. The correlations between the strength and hop tests were poor (r = 0.01 to 0.27,

p > 0.05) supporting previous suggestions that function can not be predicted by joint

specific strength testing. Clinicians must be careful not to assume a strong relationship

between joint specific isokinetic tests and hction.

Key words: Isokinetic hip strmgth, functional test, rehability

ACKNOWLED(rEMENTS

I would like to thank John Kramer, Lorie Forwell, Trevor Birmingham, Pat

Darling, Marg Lee, Donna Beer and Tony Vandervoort for their assistance with this

project Their guidance, critical appraisal, and support during this undertaking made it

possible.

Also many thanks are extended to my parents, sister and friends. Family and

friends are the Cornerstone to any person's life. Without their attentive ears and ongoing

support, I would have never undertaken this adventure. You are always in my heart.

CONTENTS

CERTIFICATE OF EXAMINATION / ii ABSTRACT / iii ACKNOWLEDGEMENTS / iv TABLE OF CONTENTS / v LIST OF TABLES / vi LIST OF FIGURES / vii

Page

............................................ CHAPTERlINTRODUCTION 1

Purposes ........................................................ 10

................................................. CHAPTER 2 METHODS 11

Subjects ........................................................ 11

........................................... Muscular Strength Tests 17 ................................................. A) Test Position 17

.................................................. B)StrengthTest 19

..................................................... Conclusions 39

APPENDICES ......................................................... 41

........................................................ REFERENCES 56

LIST OF TABLES

Table Description

1 . Subject descriptive infomation ..................................... -13

2 . Reliability of the isokinetic hip strength tests .......................... -24

......................................... 3 . Reliability ofthe hop tests -25

4 . Mean and standard deviation (SD) of the strength and hop tests ............. 26

5 . Two way ANOVA for movements (abduction and adduction) by muscle actions .......................................... (concentric and eccentric) 27

6 . Paired t-test comparison of distance hopped in the lateral and medial direction ..................................... (values are for difference scores) 28

........................ 7 . Correlations (r) between strength and hop scores 29

LIST OF FIGURES

Figure Description Page

1. Hop test for distance performed in the medial direction. . . . . . . . . . . . . . . . . . . . 14

2. Positioning for the isokinetic hip abduction and adduction tests: posterior view. 15

3. Positioning for the isokinetic hip abduction and adduction tests: Lateral view. . . 16

INTRODUCTION

The hip joint forms an important connection between the lower extremity and the

trunk that is intricately involved in the process of ambulation and other transitional

movements (ie. squatting, power skating). However, few studies have examined hip

strength or test-retest reliability and how hip strength relates to function. Test-retest

reliability articles involving lower extremity measures have primarily focused on the knee

and ankle joints. There are only a few articles that have reported the tat-retest reliability

of measures associated with the hip joint (Vaz et a1 199 1, Burnett et al1990, CahaIan et

a1 1989).

Hockey players are characterized by a high incidence of musculotendinous non-

contact hip injuries, such as muscular strains of the groin, hamstrings, iliopsoas and

quadriceps femoris musculature (Gooch et a1 1993, Age et al 198 8, Roberts and

Williams 1988). It has been suggested that these injuries are the result of the high

acceleration and deceleration in hockey skating combined with the dynamic stability

requirements on the ice surface (Agre et a1 1988, Sim et a1 1987). Although these injuries

result in considerable loss of playing time, there has been little Investigation to date to

evaluating the severity of these muscular dysfbctions.

In the rehabilitation setting, determining readiness to retum to sport and more

complex skills in hockey players have often used open kinetic chain testing, such as

isokinetic strength testing (Peachnig et a1 1998, Shelboume and Nitz 1995, Seto et a1

1988). Open kinetic chain exercises for the lower extremity have been defined as activity

that occurs while the foot is firee to move, such as isolated isokinetic seated knee

extension and isokinetic ankle plantar flexion performed in the kneeling position

@inningham et a1 1998, Stuart et a1 1996, Wi et a1 1996, Palmitier et a1 1991).

Closed kinetic chain activities have been developed as an additional means to

prepare and evaluate a patients ability to retum to a higher fuactioaal Level taking into

account specificity of training principles (Petschnig et al1998, Greenberger and Paterno

1995, Risberg and Ekland 1994, Lephart et af 1992, Anderson et all99 1, Shelboume and

Nitz 1988, Daniel et a1 1982)- These activities have been defied as activity peflormed

while the foot is fixed and hip motion is accompanied by knee and ankle motion, such as

during a standing squat or during the ice contact component of the skating motion

(Birmingham et a1 1998, Stuart et a1 1996, Wilk et a1 1996, Palmitier et al 199 1).

Several authors have agreed that lower ememity functional tests, which are

defined as those that simulate the stresses on the joints which occur during sports, are a

valuable tool in the assessment of the athlete's ability to participate in sport (Lephart et a1

1992, Noyes et a1 199 1, Barber et a1 1990, Tegner et a1 1986, Daniel et al ; 982). The

ease and Iow cost of performing functional tests makes them ideal for use in clinical

settings (Vandenneulen et a1 1999, Noyes et a1 199 1, Daniel et al 1988).

There is an abundance of literature penaining to lower extremity closed kinetic

activities. Among those investigated are the single leg hop for distance, (Petschnig et a1

1998, Noyes et a1 199 1, Barber et a1 1990, Daniel et a1 1988, Tegner et a1 1986), the one-

legged cross-over hop for distance (Wik et a1 1994), the one-legged lateral hop

(Vandermeulen et a1 1999), and two legged tests that include the figrue-of-eight test

3

(Petscbnig et al1998, Risberg and Ekland 1994,Tegner et a1 1986) , the stair-rumkg test

(Petschnig et al1998, Risberg and Ekland 1994,Tegner et al1986), the carioca test which

involves crossing one leg over in a sideways direction (Petschnig et a1 1998, Lephart et a1

1992), and the vertical jump (Petschig et a1 1998, Anderson et a1 1991, Barber et aI

1990). The majority of these movements concentrate on forward or vertical movements

and do not take into account the lateral destabilizing forces involved in direction changes,

such as cutting.

Before tests that evaluate hip muscular injuries can be used comparatively, or

studied for significance and validity, knowledge of their test-retest reliability is required

(Fleiss 1986). Similarly, in order for hip tests to be used clinically to make confident

decisions regarding an individual's progress with treatment, knowledge of the day-to-day

variability in individual scores is necessary. Whereas reliability coefficients such as the

intraclass correlation coefficient (ICC) quantify systematic error for a group of

individuals, the standard error of measurement (SEN provides a means of quantifying

the between-session variability of an individual's scores. Using the SEM, 95%

confidence in te~a ls (CI) can be constructed ar0u11d an observed score, and this quantifies

the range within which the true score might be expected to vary as a result of

measurement error (Streiner and Norman 199 1). Because clinicians are often faced with

relatively small changes in the strength of their patients, it is important that they know

whether these changes are or are not attributable to measurement error (Stratford 199 1).

Both open and closed kinetic chain activities were used in the present study to

evaluate strength and function around the hip joint. Specifically, isokinetic hip abduction

4

and adduction movements performed concentrically and eccentrically represent open

kinetic chain activities, while one-legged hops performed in the medial and lateral

directions represented closed kinetic chain activities.

Hip abduction and adduction contribute to the n o d mechanics in power

skating. The skating motion is initiated when the skater forcibly abducts the thigh in the

push off movement and then rapidly shifts their weight to the opposite leg to initiate the

glide stroke (Humble and Gastwirth 1988, Merrifield and Cowan 1973). These motions

along with hip and knee extension contribute to the ice skating motion used in hockey.

The actions of crossing one leg over the other to change direction and stopping in a lateral

direction are also hypothesized by the present authors to involve hip abduction and

adduction movements. The current literature includes several articles related to isokinetic

evaluation of the hip abductor and adductor movements (Donatelli et a1 1991, Bumett et

al1990, Cahalan et a1 1989, Ryser et a1 1988, Tippett 1986, Poulmedis 1985, Markhede

and Grimby 1980, Molnar and Alexander 1979, Jensen et a1 197 1, May 1968, Murray and

Sepic 1968, Merchant 1965). Although these studies provide comparative information

for a number of populations, information pertaining to the reliability of isokinetic testing

of hip abduction and adduction movements is Limited (Burnett et al1990, Cahalan et a1

1989)-

Bumett et a1 (1990) studied the test-retest reliability of six isokinetic hip

movements completed by healthy young boys aged 6 to 10 years. The 29 subjects were

tested on two occasions with 1-2 weeks between test sessions. The tests were performed

in the standing position. Although the authors did not report whether the measures were

concentric or eccentric, the date of the paper and the use of the Cybex I1 suggest

concentric muscle actions. Reported ICCs for hip abduction and adduction movements

performed at 30" and 90°/sec angular velocities were considerably Iowa than those

reported for hip flexion, extension, medid and lateral rotation movements. Their hip

abduction and adduction ICC values ranged fbm 0.49 to 0.59. The authors amiuted the

poor reliability of the peak torques to the difficulty in testing the young age group,

inability to standardize joint range of motion (ROM), inadequate practice sessions and

poor stabilization. Although the specific type of ICC calculated was not stated, using the

reported ICCs and standard deviation values, an estimate of the variation in an

individual's score can be obtained. Specifically, using the calculation described by

Streiner and Norman (1991) the SEM and 95% CI for the reponed scores obtained during

hip abduction and adduction tests performed at 30°/sec can be determined. The SEMs of

t3 and *6 Nm suggest that an individual's true score could vary *6 and *11 Nm (95%

CIS) between test sessions for abduction and adduct ion movements, respectively.

Cahalan et a1 (1989) also investigated the six major hip movements and measured

isokinetic strength. Their testing protocol involved a Cybex II isokinetic dynamometer,

and subjects were stabilized in an upright (standing) fhme designed for the study. The

peak torques produced by the 72 healthy subjects aged 20-8 1 years of study were

recorded. Among these subjects, 18 young men (man age = 28 years) and 17 older men

(mean age = 54 years) participated in the study. Thirteen other normal individuals were

recruited for a separate test-retest pilot study. Although, methodological details were not

included in the article, the authors reported that in the two day pilot the mean difference

6

in the peak torque values was less than 4% for all fimctions and a test-retest correlation of

0.96 was reported The type of correlation used to determine this value was not

described, but it is much higher than the KC'S reported by kumett et a1 (1990).

Vaz et a1 (199 1) investigated the test-retest reliability of hip abductor strength in

twenty three male and twenty female subjects. However, unlike Burnen et a1 (1990), the

strength measures reported were isometric and the subjects were patients measured pre

and post total hip joint replacements. That study revealed that the isometric method of

evaluation was highly reliable (KC 2,l r 0.97) using a test-retest protocol completed on

one occasion with a 30 minute rest between tests. Using the Streiner and No- (1991)

calculation it is estimated that the SEM values for the hip abduction peak torques would

range fonn 2 to 3 Nm and the 95% CI would range fiom 4 to 6 Nm. These values are

based on the mean and standard deviations of the peak torques reported in a Vaz et a1

(1 99 1) bar graph. Another aspect of the study involved correlating the isometric torques

with a fimctional disability scale and a six minute walk test. The relationship between hip

abductor torques and the functional disability scale was low and non significant (r = -0.17

to -0.26, p > 0.05). However, the relationships between hip abductor torques and the six

minute walk was moderate and statistically significant (r = 0.48 to 0.5 1, p < 0.01).

Several other studies of isokinetic hip strength did not use test-retest protocols.

Donatelli et a1 (199 1) studied isokinetic hip abductor and adductor peak torques

completed at an angular velocity of 6O0/sec in 42 healthy subjects (mean age = 26 years)

using a MERAC system. The subjects were positioned in side lying facing away fiom the

dynamometer. The axis of rotation was aligned 0.5 inches medial to the anterior superior

7

iliac spine (ASIS) and the end of the Lever arm positioned at the lateral joint line of the

knee. Although, the type of contraction investigated was not mentioned, the age of the

paper (1 99 1) and the use of the MERAC isokinetic dynamometer suggest concentric

muscle actions. The relationship between abductor and adductor torque was investigated

by the authors and expressed in a ratio. The ratios reported suggest that the adductor peak

torques were larger than the abductor peak torques.

Two recent studies investigated the hip strength in athletic populations. Steven

Tippett (1 986) performed a pilot study that examined the hip, knee and ankle peak

torques during concentric muscle actions and the range of motion of 16 college baseball

pitchers (mean age = 20 years). Side lying hip abduction and adduction isokinetic peak

torques were measured on both legs at 30° and 1 80°/sec angular velocities. Each lower

limb was classified as either the stance or the kick leg depending on the biornechanical

function during the pitching motion. Five repetitions were pwfomed at the 30°/sec

angular velocity and 15 repetitions at the 180°/sec angular velocity. Thirty seconds rests

were given between testing speeds and a 2-minute rest between the test movements. The

test position, stabilization, and instructions used were not specified. Only two

submaximal practices were given prior to the testing. The results indicated that there was

no statistically significant differences between the stance and kick legs when hip

abduction and adduction peak torques were compared.

Another study involving athletes was performed by Poulmedis (1985). He

measured peak torques during concentric muscle actions in 18 elite Greek soccer players

(mean age = 28 years). Hip abduction and adduction peak torques were measured using

8

the Cybex I1 isokinetic dynamometer- The authors reported the patients were set up in the

standard position described in the Cybex I1 manual. Mean peak torque values and a 74%

ratio of the hip abductor to adductor peak torques were reported. This finding supports

the Donatelli et a1 (1991) finding that the adductor peak torques are higher than the

abductor torques.

The only study located by the present author that evaluated a pathological

population using isokinetic hip testing was performed by Ryser et a1 (1988). They

studied individuals having undergone above knee amputations (AKA), by comparing

peak torques during hip abduction movements at 30°, 90" and 150°/sec angular velocities

in prosthetic and intact limbs. The subjects were 8 male patients and 2 female patients

(mean age = 41 years) matched to 10 healthy individuals (mean age = 42 years).

Abduction peak torques during concentric muscle actions were 47 Nm and 76 Nm for the

prosthetic and intact Limbs respectively. Abductor strength was investigated due to the

importance of the musculature in maintaining a level pelvis during the single leg stance

phase of gait. The authors proposed changes in stabilization and positioning of the pelvis

and limb as possible improvements in study desige

Along with isokinetic testing, functional tests that involve the hip joint have been

under represented in the literature. Vandenneulen et a1 (1999) recently studied a one-

legged lateral hop test thought to produce lateral destabilizing forces that were similar to

cutting and landing off balance. This test-retest study was performed using 46 healthy

young subjects (mean age = 2 1 years). The reliability coefficients on one test occasion

were excellent (ICC 2,1 r 0.83), inferring that the lateral hop test could be used to

9

determine differences in a pathological populations. SEMs and 95% CIS of * 8 cm and * 15 cm respectively were reported for the 17 males tested (mean age = 22). Vandermeulen

et a1 (1999) did not perform a one-legged medial hop test. A subject's o v e d ability to

change direction can be better evaluated by including a hop for distance in both the IateraI

and medial directions-

The ease and low cost of perfionning the hop test for distance in the medial and

Iateral direction may also be beneficial in determining clinical return to sport parameters.

However, we were unable to find any articles that evaluated the relationships between

isokinetic strength and closed kinetic tests that focus on the hip abductor and adductor

movements. I fa strong relationship exists between the hop tests and the isokinetic

strength of the hip abductor and adductor movements, inferences regarding a hockey

players strength may be determined using a timely and cost effective hop tests.

Several studies have exambed the correlation between isokinetic strength and

closed kinetic performance in the knee (Petscbnig et ai 1998, Oreenberger and Patemo

1995, W i et a1 1994, Anderson et a1 199 1, Seto et a1 1988). Wilk et a1 (1994) studied

the single-leg cross-over triple hop for distance (SLCH), which involves lateral

destabilizing forces similar to those in the lateral and medial hops for distance. They

evaluated the inter-relationships among isokinetic quadriceps peak torques and three

functional hop tests in 50 subjects (mean age = 25 years) that had undergone arthroscopic

anterior cruciate ligament reconst~ction. Peak torques were assessed using a Biodex at

angular velocities of 1 80°, 300" and 450°fsec. There were significant Pearson product

correlations between the quadriceps peak torque and the SLCH at 180° (r = 0.69, p <

LO

0-01), 300' (r = 0.64, p < 0.01), and45O0lsec (r=0.53, p <O-05). The authors discussed

that correlations exist between bctional and isokhetic tests, but did not mention the

ability of the strength tests to predict functional ability.

The moderate correlation values reported by Wilk et a1 (1994) and other studies

(Petschnig et al1998, Greenberger and Patemo 1995, Anderson et a1 199 1, Set0 et a1

1 9 8 8) suggest that knee functional performance may not be adequately predicted by the

use of isokinetic suength testing alone. As a result, additional measures of lower limb

performance should be evaluated.

Purposes

The purposes of the present mdy were to examine : 1) the test-retest reliability of

hip abductor and adductor peak torques determined isokinetically during concentric and

eccentric muscle actions; 2) the test-retest reliability of one-legged hop tests in the medial

and lateral directions; and 3) the reiationship between hip muscle strength and the hop

tests in a group of elite hockey players.

CHAPTER 2

METHODS

Subjects

Twenty-seven healthy young males volunteered to be subjects for the study (Table

I), which had been approved by the University of Western Ontario's Health Sciences

Research Committee (Number E626 1 - Appendix A). The subjects were elite amateur

and professional hockey players fkom the following levels of hockey: Ontario West Junior

B; Ontario Hockey League Junior A; CIAU University of Western Ontario; and East

Coast League professional hockey. The subjects reported themselves to be free h m

major injury to the low back, pelvis, hip, knee and ankle over the past three years. A

major injury was defined as requiring the use of crutches or resulting in lost playing time.

Any subject with vertigo, decreased balance control, inner ear difficulties or major

neurological deficit was excluded from the study. AU subjects received an information

letter and were required to sign a form of consent prior to participation in the study

(Appendix A).

Test Protocol

Each subject performed the testing procedures (hop and strrngth tests) on two

separate occasions with a minimum of three days rest between occasions. All subjects

participated in a five minute pre-test information session when they first came to the

Muscular Assessment Lab. This included receiving a typed information letter that

described the purpose and procedures of the study, length of time required, physical risks

involved, advised them of their right to withdraw, and described subject anonymity

12

(Appendix A). They also completed an information sheet to aquire demographic data,

and potential exclusion criteria were discussed (Table 1). Testing commenced following

signing of an informed consent form (Appendix A). Participants were required to attend

the test sessions wearing shorts and nmning shoes, and to use the same apparel while

performing the tests on each occasion.

Following, consent the subjects rode on a cycle ergometer and performed three

specific stretches for the hip abductor and adductor musculature (pixiformi-s, iLioh'bial

band, and groin stretch) as a warm-up and in an effort to minimize the risk of physical

discomfort post-testing . Each subject determined their own comfortable rate of pedal

revolutions and resistance to perform a moderate intensity warm-up on the ergometer.

The subjects peddled for five minutes. The warm-up period was standardized for all

participants on both occasions.

Standardized verbal and visual instruction for the strength and hop testing were

given on both occasions (Appendix B). AlI the tests were performed with the dominant

lower extremity, defined as that used to kick a ball - test leg. AU tests were completed by

the same tester and assistant. The order of hop and strength tests was randomly assigned

for each subject

Hop Tests

All subjects performed a one leg hop test in both the medial and lateral directions

(Figure 1). The order of the hop direction was randomized and kept consistent for both

occasions, and all hops were completed in one direction before completing the hops in the

other direction. The subjects completed six practice hops which included three maximal

Mean SD --

Age - 20.2 2-7

Height (em) 181.6 5.3

Weight (kg) 83 -5 7.4

Experience Level Number of Hockey Playem

CIAU 13

Western Junior B 10

Ontario Hockey League 1

Professional 3

TABLE 1. Subject descriptive information (n = 27).

FIGURE 2. Positioning for the isokinetic hip abduction and adduction tests: posterior view*

FIGURE 3. Positioning for the isokinetic hip abduction and adduction tests: lateral view-

17

practice hops prior to data acquisitiom Each test consisted of three maximal hops. A

starting Line was marked on the tile floor with white tape. Subjects were instructed to hop

to their maximum distance, beginning on the test leg and landing on the same leg and

ensuring they maintained their balance on landing for five seconds. Any of the following

was considered a loss of balance: movement of the test foot on landing; touching down

with the opposite foot; and the use of either hand to maintain position. If balance was not

sufficiently maintained, the test was repeated until three measurements were obtained for

each occasion. The subjects' arms were f ie , allowing them to assist with balance and to

gain momentum in the jump. The distance hopped was immediately marked by a piece of

masking tape, measured and then removed prior to the next hop. The distance for the

medial hop was recorded from the lateral aspect of the foot on the starting line to the

point on the lateral aspect of the foot closest to the starting line on completion of the hop.

The distance of the lateral hop was recorded in the same manner using the medial aspect

of the foot as the marking point. The subjects were given 30 seconds rest between each

hop and three minutes of rest between the hop directions. Subjects were not informed of

their results during testing and no reference markers were placed on the floor.

Muscular Strength Tests

A) Test Position

The Kinetic Communicator (Kin-Corn, Model 500-H, Chattecx Corp, TN)

isokinetic dynamometer was used to collect the hip abductor and adductor strength data

throughout the study. Each subject was positioned in side lying on a adjustable

mobilization table (Figures 2 and 3). They faced the dynamometer head of the Kin-Corn

with the test leg positioned uppermost. One or two pillows were provided for under the

patient's head to maintain horizontal alignment of the head and trunk The subject's test

leg was uppermost and the hip and knee angles were at 0° of extension with neutral

rotational alignment. The non-test leg was positioned in approximately 30° hip flexion to

avoid contact with the test leg during adduction movements.

The axis of rotation of the hip joint was determined by land marking

approximately I cm medid to the anterior superior iliac spine (Donatelli et a1 1 99 1).

This axis was aligned co-axially with the rotational axis of the dynamometer head. In

order to achieve the proper axis alignment the subject was moved horizontally to the head

or foot of the bed and/or the mobilization bed moved vertically up or down. A circular

pad (1 0 cm diameter) was placed in fiont of the dynamometer axis to provide additional

pelvic comfort and stability.

The subjects were stabilized by two, 10 cm velcro straps secured around ihe

proximal aspect of the non-test thigh and around the waist just proximal to the iliac crest.

Two towels were placed under the waist strap on the upper lateral thorax to m h h k e any

discomfort. The subject was asked to hold onto the plinth with the upper arm during the

testing. The lateral femoral condyle was palpated and the end of the dynamometer arm

was positioned 2-3 cm proximal to this position. The exact position of the dynamometer

arm was determined by moving the test leg through the I11 range of motion @OM). The

position chosen for testing was the one that allowed the dynamometer resistance pad to

remain at the same position along the thigh during movement of the test leg without

sliding along the thigh. The dynamometer arm was secured with straps around the test

leg. The neutral position of the hip was determined using a goniometric measurement

and the Kin-Corn system was cali'brated to the subject's neutral (0") position. During

testing the examiner applied horizontal force to the posterior aspect of the sacrum, in h e

with the hip/shoulder pad, to offer f.urther stability-

Gravity correction was calculated for each test leg and used to determine peak

torque. The subjects weight was taken h m the information sheet and multiplied by 16

% to determine the approximate weight of the lower extremity (Plagenhoef et aI 1983).

This value was manually entered into the dynamometer at the time of gravity correction.

B) Strength Test

Isokinetic strength tesfing was completed at 60°/s angular velocity using the

following muscle actions and movements: 1) concentric-hip abduction; 2) concentric-hip

adduction 3) eccentric-hip abduction; and 4) eccentric-hip adduction. Peak torques were

measured in Newton meters (Nm) torque. The order of the test muscle actions and

movements was randomized on the !3st occasion, and kept consistent for both occasions.

The concentric and eccentric hip abduction were performed through a ROM of So

adduction to 30" abduction, while the concentric and eccentric hip adduction tests were

performed through a ROM of So adduction to 35" abduction.

Following verbal explanation of the isolcinetic test movements and the procedure,

a warm-up of seven repetitions was completed. Four of the warm-ups were completed at

submaximal intensity and three were completed at maximal effort, as practice

movements. The strength tests consisted of three single repetition maximal efforts in the

direction of the test movement The subjects were given 30 seconds rest between each

20

effort (including practice) and three minutes of rest between the strength tests. Subjects

were not informed of their results during testing- Standardized verbal instructions were

given between every warm-up and test repetition (Appendix B).

Data Analysis

All of the peak torque data were generated using the Kin-Corn's computer (En-

Corn 500-H, Chattecx Carp, 19894992, Software Version 3.2 1). The hop distance was

determined by the investigators using a tape measure and recorded Peak torque (Nm)

and distance hopped (m) were determined for each repetition and averaged to produce

one single measure for each occasion. Intracass Correlation Coefficients (ICCs) were

calculated to describe the reliability ofone (KC 2,l) and two (ICC 2'2) occasions (Shrout

and Fleiss 1 979). The ICCs were interpreted subjectively as follows: > 0.75 excellent,

0.40 - 0.75 moderate, and < 0.40 poor (Fleiss 1986). Standard error of measurement

(SEM) and 95% confidence intervals (CI) were calculated to describe measurement error

or variation with repeated testing, for both peak torque and distance hopped (Stratford

and Goldsmith 1997, Streiner and Norman 199 1).

A two-way analysis of variance (ANOVA) test (two movements by two muscle

actions) was used to test for statistically significant differences among the peak torques

(SPSS 1997). Following a significant F-ratio, a Newman-Keuls test was used to

compare selected means (Wirier et a1 1971).

The relationship between isokinetic peak torques and distance hopped was

determined using Pearson Product Moment Correlation Coefficients (SPSS 1997) and

interpreted using the guidelines proposed by Weber and Lamb (1970): An alpha level of

0.05 was used to designate statistical significmce throughout analysis.

CHAPTER 3

RESULTS

Only one of the subjects reported muscdar discomfort following the first test

occasion. However, the discomfort resolved within 48 hours of initial testing and did not

inhibit subsequent performance- Ail subjects completed the full test on two occasions,

with a minimum of 48 hours between test occasions, except for one subject for whom the

time between tests was 14 days, as a result of scheduling conflicts.

ALI of the subjects subjectively reported that the concentric-abduction strength test

was the most physically challenging and dficult to perform. The easiest test subjectively

reported by the subjects was the eccentric-adduction strength test. The subjects did not

subjectively prefer one hop test over the other.

The concentric-abduction strength test was the least reliable (ICCs 0.59 for one

test occasion and 0.74 for two test occasions), whereas reliability coefficients for the

other three strength tests were similar (ICCs 0.72 - 0.74 for one test occasion and 0.84 -

0.85 for two test occasions) (Table 2). Overall, none of the four reliability coefficients

were greater than 0.75 on occasion one, whereas three of the four had excellent reliability

(> 0.75) when data were averaged over two test occasions; although, the ICC for the

concentric-abduction strength test over two test occasions remained lower (ICC 2,2 =

0.74).

Reliability of the lateral and medial hops was excellent for both o w (ICCs 0.87

for medial and 0.9 1 for lateral) and two test occasions (ICCs 0.93 for medial and 0.95 for

lateral) (Table 3). For both strength and functional test data, ICCs increased, while SEMs

23

and 95% CIS decreased when scores were averaged over two occasions (Tables 2 and 3).

Tables 4 and 5 summarize peak torques and the results of the two way ANOVA

test (movement by muscle action). The main effects for movemeat and muscle action

were significant (p < 0.01). The adduction peak torques (E = 227) were significantly

greater than the abduction peak torques (n = 202) when the movement main effects were

analysed, and the eccentric peak torques (n = 247) were significantly greater than the

concentric peak torques (n = 180) when the muscle action main effects were adysed (p

< 0.01)-

Table 4 illustrates hop distances and Table 6 shows the results of the paired t-test

for the hop test (medial vs lateral directions). There was no significant difference in the

distance hopped between the medial and lateral hops @ > 0.05).

Table 7 shows that overall, aLI of the correlations between strength and functional

scores were poor-to-low and none of the correlations were statistically significant @ >

0.05)-

Movement Concentric Eccentric Concentric Eccentric Muscle Action Abduction Abduction Adduction Addaction

-

One test Occasion

SEM (Nm) 21 18 17 20

95% CI (Nm) 42 35 33 39

Two Test Occasion

ICC(2,2) 0-74 0.85 0.84 0.84

SEM (Nm) 14 13 11 14

95% CI (Nm) 28 25 22 28

ICC = Intraclass correlation coefficient. SEM = Standard error of measurement- 95 % CI = 95 % Confidence interval-

TABLE 2. Reliability of the isokinetic hip strength tests (n = 27 subjects).

Hop Direction .

Lateral M d a l

One Occasion

rcc (2,l)

SEM (cm) 6 7

95% CI (cm) 11 14

Two Occasions

ICC (2,2) 0-95 0.93

SEM (cm) 4 5

95% CI (cm) 9 10

ICC = Intraclass correlation coefficient. SEM = Standard error of measurement. 95% CI = 95% Confidence interval.

TABLE 3. Reliability of the hop tests (n = 27 subjects).

Test Occasion Test Occasion Two 1 2 Occasion

Mean

Mean SD Mean SD Mean SD

Strength tests (Nm)

Concentric-Abduction 169 33 174 30 172 28

Eccentric-Abduction 230 35 234 35 232 33

Concentric-Adduction 183 32 194 29 188 28

Eccentric-Adduction 259 38 263 40 261 36

Hop Tests (cm)

Lateral 156 19 159 21 157 20

Medial 158 20 163 19 160 19

TABLE 4. Mean and standard deviation (SD) of the strength and hop tests (n = 27).

- -

Variable Sum of df Mean F-ratio pvahe !squares square

Main Effects

Movement 25629 26 986 14 0-00 1

Muscle Action 19054 26 733 163 0.000

Interaction

Movement x 7913 26 304 4 0.07 1 Muscle Action

df= degrees of Worn

TABLE 5. Two way ANOVA for movements (abduction and adduction) by muscle actions (concentric and eccentric) @ < 0.05).

Variable Mean SD SEM t df s k (2

Lateral score vs -2.8 12.1 2.3 -1.2 26 0.24

Medial score

TABLE 6. Paired t-test comparison of distance hopped in the lateral and medial direction (values are for difference scores: cm)-

Muscle Action Movement Hop Direction

Lateral Medial

Concentric-Abduction

Eccentric-Abduction

Concentric-Adduction

Eccentric-Adduction

TABLE 7. Correlations (r) bebeem strength and hop scores (n = 27 subjects).

CHAPTER 4

DISCUSSION

The reliability coefficients for the present isokinetic strength tests were modest

(ICC 2,1< 0.75) for data collected on one occasion and generally exceUent (ICC 2 2 2

0.75) for data averaged over two occasions. The least reliable test, concentric-abduction,

approached but did not achieve excellent reliability when scores were averaged over two

test occasions (ICC = 0.74). The subjective reports that the concentric-abduction strength

test was the most difficult to perform may explain the lower reliability compared to the

other three strength tests. The remaining three tests approached excellent (KC 2,l = 0.72

to 0.74) reliability on one test occasion (Table 2). These values describe the per fomce

of the group of subjects. When expressed in tenns of variability of an individual's

performance, the reliability of the peak torques was lower and characterized by greater

measurement error. For example, measurement error (95% confidence intervals) for

concentric hip adduction was * 33 Nm, when determined on one occasion, and decreased

to * 22 Nm when determined over two test occasions (Table 2). As a result, using the

mean peak strength scores observed in the present study (Table 4) the peak torque of a

typical healthy male hockey player, as determined on one test occasion, could be expected

to lie between 1 SO and 2 16 Nm (1 83 * 33 Nm). If the data averaged over two test

occasions were used, the true peak torque score could be expected to lie within a

narrower range: 166 and 210 Nm (188 * 22 Nm). In other words, even if two test

sessions were performed and the subject improved his score as much as 20 Nm, this

change could still be attributed to measurement emor. As a result, even with a high

31

reliabsty coefficient, considerable change (> 12%) in the individual's score is required to

be confident that a true gain or loss in hip strength had occurred.

Ln view of the costs and clinical time associated with additional testing (two

occasions), techniques to maximize reliability on one test occasion need to be explored.

Study design changes that may improve the reIiability include increasing the number of

practice and test movement repetitions, having the subjects practice the test movements

at home before testing, or altering the test position (ie supine). The small range of

motion, size of the joint, uncommon isolated movement performed and unusual test

positioning may also have contniuted to the poor reliability of data measured on one

occasion.

The subjects in the present study were skilied athletes. Their ability to learn and

perform abnormal movement patterns, such as the isolated hip movements of isokinetic

abduction and adduction, may be much greater than a typical patient population. Lower

reliability coefficients may be observed when less skilied subjects are tested using similar

protocols. Further study is required to determine test-retest reliability for other

populations.

In the test-retest reliability study by Bumett et aI (1990), the ICCs reported for

abduction and adduction peak torques at the angular velocities of 30°/sec (ICC = 0.59 and

0.55) and 90°fsec (KC = 0.59 and 0.49) were generally lower than those in the present

study. However, it is diflicult to compare results due to the fact that the exact nature of

the K C computation reported by Bumett et a1 (1990) was not specified. In the present

study, only the concentric-abduction reliability coefficient determined on one test

32

occasion ( K C 2,1= 0.59) was as low as the Burnett et a1 (1990) values- The other three

hip strength tests used in the present study (eccentric-abduction, concentric-adduction and

eccentric-adduction) had greater reliability coefficients than the Burnett et a1 (1990) study

for both one (ICC 2,1= 0.72 to 0.74) and two ( K C 2,2 = 0.84 to 0.85) test occasions.

The present author attributes the greater reliability to alterations in the

methodology that were employed in the study. Although Bumett et a1 (1990) also secured

the pelvis and the non test lower extremity with straps in side lying, they suggested that it

was ineffective at preventing substitution of orher muscle groups which may have lead to

increased variability in the peak torque scores. In the present study, the examiner

provided force to the posterior aspect of the sacrum to minimize pelvic rotation and

further improve stabilization. Another variable that was not controlled by Burnett et a1

(1990) was the ROM of the test movements. The subjects were directed to move through

a certain ROM, but had no visual marker to determine when the end of ROM was

reached. The e x h e r s descn'bed 20% differences in hip abduction ROM over the two

test sessions. The Kin-Corn program used in the present study provided mechanical stops

at the end ROM that the examiner established prior to testing using goniometric

measurement. Therefore, the range of motion used by all of the subjects was standardized

and the subject knew when they had reached the end points of the required ROM.

Burnett et a1 (1990) also recommended that the 2-3 submaximal repetitions may not be

adequate for sufficient learning of the movement. The present study attempted to

improve the learning of the difEcult test movements by allowing seven practice

repetitions, four at submaximal intensity and 3 at maximum intensity. Finally, Burnett et

33

a1 (1990) also suggested that fatigue may have contn'buted to the poor reliability. They

used four continuous repetitions performed by the subjects, without rest. In the present

study, the strength tests were single repetition efforts followed by 30 second rest

intervals, in an effort to minimize fatigue

The reliability coefficients for isometric hip abduction peak torques (KC 2,1=

0.97 to 0.99) reported by Vaz et al(1993) were much higher than the one occasion

isokinetic concentric-abduction (KC 2,l = 0.59) and eccentric-abduction (ICC 2,l =

0.74) coefficients reported in the present study. The heterogeneity of the Vaz et al(1993)

sample (23 males and 20 females) may be one of the explanations for the higher values.

Since reliability coefficients are an expression of the variability between the subjects

relative to the total variability, they can be artificially inflated when a heterogeneous

sample is investigated. For example, using a group of subjects with a higher level of

variability, such as mixed male and female subjects, will result in improved reliability

coefficients. Other testing procedures, such as the belt resisted stabilization used by Vaz

et al(1993), may also have lead to improved consistency of test efforts. The

circumferential straps around the pelvis and the distal thighs allowed minimal movement

of the lower extremities, which may have minimized the substitution by other muscle

groups. Despite efforts to improve stabilization provided in the present study, the

strength of the athletes tested and the unique nature of the movements made it difficult to

eliminate substitution by other muscle groups during a maximum single repetition effort.

The excellent test-retest reliability found by Vaz et a1 (1 993) suggests that their isometric

method of testing may be a possible alternative to the isokinetic abduction tests used in

34

the present study- However, the extent to which isometric and isokhetic tests can be

used to predict the same functicd test is unclear.

The one-legged lateral hop test studied by Vandermeulen et a1 (1999) was

performed in an identical manner to the lateral hop for distance in the present study with

two exceptions. The hops in the Vandenneulen et a1 (1999) study were performed in bare

feet, while the subjects in the present study wore ;lmning shoes. The other difference was

the extremity used by the subjects to perform the hops. The present study tested the

subjects' hops on the dominant extremity (right side), while Vandenneulen et al(1999)

tested the subjects' hops on both the dominant and the non-dominant lower extremities.

In their study 46 normal males and females achieved right sided ICC 2'1 values of 0.83

and 0.86 for the lateral hop test, respectively. Among these subjects were 1 7 males that

recorded mean hop distances for both occasions of 1.3 1 * 0.17 m. The male subjects

studied by Vandenneulen et a1 (1997) also had * 0.08 m SEM and * 0.15 m 95% CI

values for the right leg. Higher ICC values (ICC 2,l = 0.9 1) and hop distances (1.57 * 0.20 m), as well as the lower SEM and 95% CIS (SEM = * 0.06 m and 95% CI = * 0.1 1

m) were reported in the present study. This may be partially attributable to the athletic

skill level of the hockey players. The ability of these subjects to learn a skilled

movement, such as the lateral hop for distance, may be much greater than the normal

healthy male subjects in the Vandermeulen et a1 (1999) study. The smaller sample size (n

= 17) and decreased confidence in performing the hop tests in bare feet may also account

for the differences.

Excellent reliability of the medial hop test was also observed in the present study

35

(ICC 2,1= 0.87). An advantage of investigating the medial hop in addition to the lateral

hop test is that destabilizing forces in athletic activities can occur in both directions. By

testing both medial and lateral directions, clinicians can observe a more representative

sample of an athlete's side to side movements-

The excellent reliability of the hop tests in the present study may make them quick

and cost-effective closed kinetic tests that only require one test occasion. Future research

studies should focus on determining the sensitivity and baseline values for the lateral and

medial hop tests in clinical populations.

In the present study the hockey players produced si@cantly larger adduction

torques than abductor torques. The eccentric peak torque scores were also significantly

higher than the concentric scores. Although previous studies (Donatelli et at 199 1,

Burnett et a1 1 990, Cahalan et aI 1 989, Tippett 1986, Poulmedis 1985) are in agreement

with the present findings, studies comparing isokinetic tests using concentric and

eccentric muscle actions in the hip were got avaiiabk

The velocity of the isokinetic testing in the present study was 60°/sec. Previous

studies have used a variety of testing velocities, with a tendency for the peak torques to

decrease as the velocity of the test movement increased (Burnett et a1 1990, Cahalan et al

1989, Ryser et al 1988, Tippett 1986, Poulmedis 1985). Donatelli et al(W9 1) dso tested

at the 60°/sec angular velocity. However, they used a different testing device (MERAC),

a different testing position (side lying facing away from the dynamometer head), their

subjects were healthy males and females, and the dynamometer lever arm had two contact

points. They reported that concentric peak torque for the 48 subjects (mean age = 26

36

years) to be 68 * 20 Nrn for abduction and 167 * 57 Nm for adduction. Both the

concentric-abduction (172 * 28 Nm) and concentric-adduction (I88 * 28 Nm) peak

torques in the present study were higher than those reported by Donatelli et aI (199 I).

Abduction peak torqye for female subjects was 147 * 33 Nm, while peak torque for males

was 207 * 73 Nm. The athletic sample in the present study may have produced higher

peak torques due to the increased lower extremity strength and stability acquired in the

skating motion. In agreement with the present study, the mean peak adductor torques

were statistically greater than the mean peak abductor torques (Donatelli et a1 199 1).

However, there was a much greater abduction to adduction mean peak torque difference

noted in the Donatelli et a1 (1991) study (99 Nm) compared to the present study (16 Nm).

This large difference may also be accounted for by characteristics of the subjects in the

present study. The importance of the hip abductor and adductor muscle groups in the

mechanics of skadng (ie. cross overs, change of direction, stopping, and acceleration

from a stopped position) for hockey players may have lead to a more balanced

development of these agonist and antagonist muscles.

Another study that measured the isokinetic hip abductor and adductor peak

torques in the side lying position on a Cybex II was performed by Cahalan et a1 (1 989).

Torques for the young males at 30°/sec averaged 103 * 26 and 121 t 26 Nm for

concentric-abduction and adduction, respectively. These were the highest torques

reported in their paper. In comparison, the mean peak torques for concentric-abduction

and adduction movements in the present study were 172 * 28 and 188 * 28 Nm,

respectively. The athletic skill level of the individuals, younger age and improvements in

37

test methodology may explain the difference between the studies seating and Matyas

1996).

Tippett (1986) measund concentric hip abduction and adduction torques in side

lying on 16 college baseball players using their stance and kick legs. Mean abduction

peak torques for the stance leg (109 * 36 Nm) and the kick leg (1 18 * 39 Nm) measured

at 3 OO/sec were lower than those for the present hockey players (1 72 28 Nm).

Similarly, the mean adduction peak torques measured on the stance leg (141 * 53 Nm)

and kick leg (145 t 44 Nm) were lower than those for the right leg of the hockey players

(1 88 * 28 Nm). The age level (mean age = 20 years) and athletic skill level of the

baseball players were similar to the present study, however the smaller number of

subjects tested and the methodology descni may help to explain the lower values.

Tippett (1986) ailowed only two submaximal warm-up repetitions for each motion. This

may not have given the subjects adequate time to practice and leam the abnormal hip

abduction and adduction movements prior to testing. Furthermore, the short rest

duration, 30 second rest between each test velocity, combined with the 5 continuous

(Cybex IC) test repetitions may have contributed to subject fatigue and lower peak torque

values.

Isokinetic (30°/sec) concentric-abductor (1 19 * 24 Nm) and adductor (1 60 1 7

Nm) strength in 18 elite Greek soccer players (Poulmedis 1985) was also lower than the

values reported in the present study. The age of the soccer players (mean age = 28 years)

compared to the younger hockey players (mean age = 20 years) and the small sample size

(n = 18) may account for the lower values observed.

38

In the present study, the correlations between hop dis*ince~ and the isokinetic hip

torques were slight-to-poor and not statistically significant This indicates that the

isokinetic evaluation of hip strength during isolated hip abduction and adduction

movements is a poor predictor hip pafomutnce. In agreement with this finding, several

authors have previously stated that a subject's dynamic functional ability cannot be

adequately ascertained through isokinetic testing (Greenberger and Paterno 1995, Lephart

et al1993). Many other factors, independent of strength, can contribute to the hctionaI

performance of an athlete, such as balance, co-ordination, power, muscle recruitment,

flexibility, endurance, skill level, environment and confidence in performance.

Lack of test-function specificity may have contributed to the poor correlations

observed. The isokinetic and hop tests used in the present study may not have been

representative enough of skills used by hockey players in game or practice situations.

Although the side Lying isokinetic hip strength tests involved movements that were

specific and isolated to the hip joint, they appear not be good predictors of the strength

requirements of athletes when performing specific hockey skills. The test-hction

specificity of the medial and lateral hops for distance is also questionable. The extent to

which hops can predict skating or even more high level hockey hct ions appears to be

Limited. Future studies that investigate specific on-ice activities, such as skating speed

over a selected distance, may be required to better assess a hockey players' readiness to

return to sport or higher hctional activity.

Vaz et a1 (199 1) found correlations between isometric hip strength and functional

measures that ranged h m slight-to-moderate (r = 0.10 to 0.5 1). The relationship between

39

hip abductor torques and the 6 minute walk test was significant (r = 0.48 to 0.51, p <

0.01). These strength-function correlations were much higher than those in the present

study. The difference in findings may be due to the skill components involved, as well as

the sample studied Whereas, the 6 minute walk test involves a basic functional task that

is performed by all the subjects on a daily basis, the hop tests in the medial and lateral

directions are not activities of daily living. The medial and lateral hop tests involve

components that utilize skills such as balance, co-ordination, and power. The relationship

between an isolated strength test and a fimctional test may be higher in a sample of

subjects who do not have the skill level of trained athletes. Similar relationships may be

the case when investigating pathological groups that are not hctioning at a normal level.

Clinical Relevance

In order to maximize reliability and reduce the measurement error encountered

during isokinetic testing for hip abduction and adduction strength, clinicians should test

subjects on two occasions. However, only one testing session is required for hop tests.

Clinicians must be careful not to assume a strong relationship between joint specific

isokinetic tests and fhction. Isokinetic tests done are not sufficient to determine if an

athlete is ready to return to sports, such as hockey.

Conclusions

Test-retest reliability for isokinetic hip strength testing was moderately high

reliable, but the 95% CIS were wide. At least two test occasions were r e w e d to achieve

acceptable test-retest reliability when using the current test methodology. Test-retest

reliability for the lateral and medial hop tests was excellent and characterized by smaller

95% CIS. The relationship between strength and function was slight-to-poor, md

suggests that fimction cannot be predicted fiom joint specific strength testing. Future

studies need to consider ways to increase reliability in isokinetic hip strength testing and

examine other populations using the functional and isokinetic tests.

APPENDICES:

Appendix A: Ethics Approvd, Letter of Information and I n f b d Consent

Appendix B: Verbal Instructions

NOTE TO USERS - - . . - -

Page(s) not included in the original manuscript - '-- are unavailable from the author or university. The-

manuscript was microfilmed as received.

This reproduction is the best copy available.

UMI

Relationship Between Strength of the Hip MusculPture and Hop Tests

The study seeks to determine the strength of the muscles used to move your leg. It will also determine if hip movements can be measured reliably and how they are related to a sideways hop test. This hop test may be used in preseason testing or in making treatment and return to play/work decisions.

If you agree to participate, you wil l be tested on two occasions, about one week apart, in the Muscular Assessment Laboratory, School of Physical Therapy, University of Western Ontario (Room 1408). Each test occasion will take about 60 minutes. Muscle strength of your dominant leg will be tested while positioned in side lying and using exercises which require you to move your thigh away and towards your body while you push against a resistance pad. You will also be asked to hop sideways h m one leg and landing on that leg without losing balance, three times.

Before each test of muscle strength, you will have the opportunity to practice the test movements and ask any questions you may have. The strength test involves 3 maximal effort repetitions for each leg of four different movements producing a total of 12 maximal efforts over about a 45 minute period. Frequent rest periods will be provided.

Due to the fact that you will be performing exercises with maximum effort, some muscle soreness may develop. Any such discomfort is expected to be minor and similar to that which you have experienced after completing other exercises. Should you experience any leg discomfoa while testing, testing will be stopped immediately.

Please feel fkee to ask any questions that you may have concerning the study. Participation in the study is voluntary- You may refuse to participate, or withdraw &om the study at any time with no effect on your academic standing.

Your identity and results of the study will remain confidential to the primary investigators involved with the study.

Please call Jason Kea (EXome: 473-0585 or work: 661-2 1 1 1 ext 883 1) for fiuther information about the study.

Jason Kea Bsc (P.T.) Clinical Fellow in Sports Physiotherapy Fowler-Kennedy Sports Medicine Clinic

John Kramer Director of the School of Physiotherapy Elborn College, U.W.O.

44

Relationship Between Strength of the Hip Musculature and Bop Tests

I have read the accompmying letter of information, have had the nature of the

study explained to me and I agree to participate. Any questions have been answered to -

my satisfaction.

Signed

Dated

Lateral Hop Test (Zatemf Diredon Fim)

The test that you will do first is called the lateral hop test. W e are interested in testing how consistently you can hop to your maximum distance. You will stand on your [rightheft] leg with the inside of your fmt Lined up with the tape. Your instructions are to hop as far as you can to your [right/left] side, hopping fbm one leg and landing on the same leg. You must maintain your balaoce on the landing leg for 5 seconds. It wil l not affect the testing ifyou lose your balance or put your other foot down. We will simply continue attempting test hops until 3 tests are completed.

Prior to the test jumps you will be allowed a number of progressively longer practice jumps. The testing will not be started until you are comfortable that you are performing consistently maximum hops.

Let's try some practice jumps first. To start try a few short jumps.

Now let's try some jumps where you jump as far as you can consistently. Remember, do not feel bad if you are unable to maintain your balance during testing. Do you feel comfortable with the test movement ?

I will give you a 30 second break and then we will begin the test hops. With all three of the tea hops you are asked to consistently hop as far as you can. Try to hop as far as you can.

We will repeat the same hop as far as you can.

The next test is exactly the same as the first test, except you will stand on your [rightfleft] leg with the outside of your foot lined up with the tape and you wiU jump as far as you can to the neft/'ght]. Other than this change we wil l perfom the test the same as the first test. Again the importance is jumping as f a as you can consistently.

Lateral Hop T& (2HediaO Dire~nin First)

The test that you will do first is called the lateral hop test We are interested in testing how consistently you can hop to your maximum distance. You will stand on your [rightAeft] leg with the outside of your foot lined up with the tape* Your instructions are to hop as far as you can to your PeWright] side, hopping fiom one leg and landing on the same leg. You must maintain your balance on the landing leg for 5 seconds. It will not affect the testing if you lose your balance or put your other foot down. We will simply continue attempting test hops until 3 tests are completed

Prior to the test jumps you will be allowed a number of progressively lmger practice jumps. The testing wilI not be started until you are comfortab1e that you are performing consistently maximum hops.

Let's try some practice jumps first. To start try a few short jumps.

Now let's try some jumps where you jump as fsr as you can consistently. Remember, do not feel bad if you are unable to maintain your balance during testing. Do you feel comfortable with the test movement ?

I will give you a 30 second break and then we will begin the test hops. With a l l three of the test hops you are asked to consistently hop as far as you can. Try to hop as far as you can.

We wil l repeat the same hop as far as you can.

The next test is exactly the same as the first test, except you wi l l stand on your [rightneft] leg with the inside of your fmt lined up with the tape and you will jump as far as you can to the [rightfieft]. Other than this change we will perform the test the same as the k t test. Again the importance is jumping as far as you can consistently.

The machine that we will perform the hip strength tests on is called the Kinetic- Communicator- This is an isokinetic strength testing device. This means that the machine will measure the amount of strength your muscles produce as you move your leg. The device will maintain a slow co-t speed as you push or pull. We are interested in how consistently you can perform your maximum effort, especially on two separate days. The key to the tests is to push or pull in the test direction as hard as you can and to maintain this maximum push or pull throughout the test movement- I will be using my hands to keep your peIvis secure fiom behind

Second Day - Intmduction

Remember, we are interested in how consistently you can perform your maximum effort, especially on two separate days. The key to the tests is to push or pull in the test direction as hard as you can and to maintain this maximum push or pull throughout the test movement.

This strength test measures your ability to push the testing pad towards the ceiling. The machine wilI monitor how consistently you can perform your maximum push. You must continue pushing up until the machine stops the movement after about 40 degrees of travel. The machine will not record until you have started pushing up into the pad-

We will start with 4-6 practice movements to familiarize you Rith the test movement,

Try the fim movement with minimal effort when you are ready.

Notice how the movement does not start until you have initiated it Remember to keep pushing all the way through the movement. Let's try another with 50% effort when you are ready.

~t Now try the same with about 75% effort when you are ready.

Do you feel comfortable enough with the movement to attempt a maximum push.

If yes - We will try after a 30 second break I If no *

When you are ready push up as hard as you can and keep pushing all the way through the movement [Pretest I]. We will try another practice after a 30 second break.

When you are ready push up as hard as you can all the way through the movement [Pretest 2/31. Do you feel confident enough to attempt the test movement?

If yes - Go to ** / IfNo - repeat Pretest 3

**We are going to perform 3 test movements exactly the same as the last practice movements with 30 second breaks.

This strength test measures your ability to pull the testing pad down towards the floor. The machine will monitor how consistently you can perform your maximum pull. You must continue pulling down until the machine stops the movement after about 40 degrees of travel. The machine will not record untii you have started to pull your leg down and it will not move under the weight of your suspended limb.

W e will start with 4-6 practice movements to familiarize you with the test movement-

Try the Grst movement with minimal effort when you are ready.

Notice how the movement does not start until you have initiated i t Remember to keep pulling all the way through the movement Let's try another with 50% effort when you are ready.

* Now try the same with about 75% effort when you are ready.

Do you feel comfortable enough with the movement to attempt a maximum pull.

If yes - We will try after a 30 second break / If w *

When you are ready pull down as hard as you can and keep pulling all the way through the movement [Pretest I ] . We will try another practice a& a 30 second break.

When you are ready pull down as hard as you can all the way through the movement [Pretest 2/31. Do you feel confident enough to attempt the test movement?

If yes - Go to ** / If No - repeat Pretest 3

**We are going to perform 3 test movements exactly the same as the last practice movements with 30 second breaks.

This strength test measures you. ability to prevent the testing pad h m pulling your leg up towards the ceiling. The machine will monitor how consistently you can perform your maximum pull. You wil l be unable to stop the pad from pulling your leg up, however, your maximum pull is still required- You must continue pulling down until the machine stops the movement after about 40 degrees of travel. The machine wi l l not record until you have started to pull your leg down.

We will start with 4-6 practice movements to familiarize you with the test movement.

Try the first movement with minimal effort when you are ready. Notice how the movement does not start until you have initiated it. Remember to

keep pulling all the way through the movement. Let's try another with 50% effort when you are ready.

* Now try the same with about 75% effort when you are ready.

Do you feel comfortable enough with the movement to attempt a maximum pull.

If yes - We will try after a 30 second break f If no *

When you are ready pull down as hard as you can and keep pulling all the way through the movement [Pretest I]. We will try another practice after a 30 second break-

When you are ready pull down as hard as you can all the way through the movement [Prerest 2/31. Do you feel confident enough to attempt the test movement?

If yes - Go to ** I If No - repeat Pretest 3

**We are going to perform 3 test movements exactly the same as the last practice movements with 30 second breaks-

Hip ABductiion - Eccentric flnifibf test?

This strength test measures your ability to prevent the testing pad fkom pushing your leg down towards the floor. The machine will monitor how consistently you can perform your maximum push. You will be unable to stop the pad fiom pushing your leg down, however, your maximum push is still required- You must continue pushing up until the machine stops the movnnent after about 40 degrees of travel. The machine will not record until you have started to push your leg up.

We will start with 4-6 practice movements to familiarize you with the test movement.

Try the first movement with minimal effort when you are ready. Notice how the movement does not start until you have initiated it. Remember to

keep pushing all the way through the movement. Let's try another with 50% effort when you are ready,

~t Now try the same with about 75% effort when you are ready.

Do you feel comfortable enough with the movement to attempt a rnaximuum push.

Eyes - We will try after a 30 second break I If no *

When you are ready push down as hard as you can and keep pushing all the way through the movement [Pretest I]. We will try another practice after a 30 second break

When you are ready push down as hard as you can all the way through the movement [Pretest 2/31. Do you feel confident enough to attempt the test movement?

If yes - Go to * * / If No - repeat Pretest 3

**We are going to perfom 3 test movements exactly the same as the last practice movements with 30 second breaks.

This strength test measures your ability to push the testing pad towards the ceiling- The machine will monitor how consistently you can perform your maximum push. You must continue pushing up until the machine stops the movement after about 40 degrees of travel.

We will start with 4 6 practice movements to fdarize you with the test movement-

Try the k t movement with minimal effort when you are ready.

Remember to keep pushing all the way through the movement. Let's try another with 50% effort when you are ready.

* Now try the same with about 75% effort when you are ready.

Do you feel comfortable enough with the movement to attempt a maximum push.

If yes - We will try after a 30 second break / If no *

When you are ready push up as hard as you can and keep pushing all the way through the movement [Pretest I ] . W e will try another practice after a 30 second break.

When you are ready push up as hard as you can all the way through the movement [Pretest 2\31. Do you feel confident enough to attempt the test movement?

If yes - Go to ** / If No - repeat Pretest 3

**We are going to perform 3 test movements exactly the same as the last practice movements with 30 second breaks.

This strength test measures your ability to pull the testing pad down towards the floor. The machine wil l monitor how consistently you can perform your maximum pull. You must continue pulling down until the machine stops the movement after about 40 degrees oftravel. The machine wiU not record until you have started to pull your leg down and it will not move under the weight of your suspended Limb.

We will start with 4-6 practice movements to familiarize you with the test movement.

Try the first movement with minimal effort when you are ready-

Remember to keep pulling al l the way through the movement. Let's try another with 50% effort when you are ready.

* Now try the same with about 75% effort when you are ready.

Do you feel comfortable enough with the movement to attempt a maximum pull.

If yes - We will try after a 30 second break / If no *

When you are ready pull down as bard as you can and keep pulling all the way through the movement [Pretest I ] . We will try another practice after a 30 second break.

When you are ready pull down as hard as you can all the way through the movement [Pretest 2/31. Do you feel confident enough to attempt the test movement?

If yes - Go to ** I If No - repeat Preresst 3

**We are going to perform 3 test movements exactly the same as the last practice movements with 30 second breaks-

This strength test measures your ability to prevent the testing pad from pulling your leg up towards the ceiling. The machine will monitor how consistently you can perform your maximum pull. You will be unable to stop the pad @om pulling your leg up, however, your maximum pull is s t i l l required- You must continue pulling down until the machine stops the movement after about 40 degrees of travel.

We will start with 4-6 practice movements to familiarize you with the test movement,

Try the first movement with minimal effart when you are ready.

Remember to keep pulling all the way through the movement. Let's try another with 50% effort when you are ready.

* Now try the same with about 75% effort when you are ready.

Do you feel comfortable enough with the movement to attempt a maximum pull.

If yes - We will try after a 30 second break / If no *

When you are ready pull down as hard as you can and keep pulling all the way through the movement [Pretest I]. We will try another practice after a 30 second break.

When you are ready pull down as hard as you can all the way through the movement [Pretest 22/31. Do you fed confident enough to attempt the test movement?

If yes - Go to ** / IfNo - repeat Pretest 3

**We are going to perform 3 test movements exactly the same as the last practice movements with 30 second breaks.

This strength test measures your ability to prevent the testing pad from pushing your leg down towards the floor. The machine will monitor how consistently you can perform your maximum push. You will be unable to stop the pad h m pushing your leg down, however, your maximum push is stil l required. You must continue pushing up until the machine stops the movement after about 40 degrees of travel.

We will start with 4-6 practice movements to familiarize you with the test movement-

Try the first movement with minimal effort when you are ready-

Remember to keep pushing all the way through the movement. Let's try another with 50% effort when you are ready.

r~ Now try the same with about 75% effort when you are ready.

Do you feel comfortable enough with the movement to attempt a maximum push.

If yes - We will try after a 30 second break I If no *

When you are ready push down as hard as you can and keep pushing all the way through the movement [Pretest 11. We will try another practice after a 30 second break.

When you are ready push down as hard as you can all the way through the movement [Pretest 2/31, Do you feel confident enough to attempt the test movement?

If yes - Go to ** / If No - repeat Pretest 3

** W e are going to perform 3 test movements exactly the same as the last practice movements with 30 second breaks.

56

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