Immediate Effect of Tensor Fascia Latae

Stretching Exercise on Muscle Activity and

Hip Motion During Active Side−lying Hip

Abduction in Subjects With Tensor Fascia

Latae Shortness

Myungki Ji

The Graduate School Yonsei University

Department of Physical Therapy

Immediate Effect of Tensor Fascia Latae

Stretching Exercise on Muscle Activity and

Hip Motion During Active Side−lying Hip

Abduction in Subjects With Tensor Fascia

Latae Shortness

Myungki Ji

The Graduate School Yonsei University

Department of Physical Therapy

Immediate Effect of Tensor Fascia Latae

Stretching Exercise on Muscle Activity and

Hip Motion During Active Side−lying Hip

Abduction in Subjects With Tensor Fascia

Latae Shortness

A Masters Thesis Submitted to the Department of Physical Therapy

and the Graduate School of Yonsei University in partial fulfillment of the

requirements for the degree of Master of Science

Myungki Ji

June 2013

This certifies that the masters thesis of

Myungki Ji is approved.

Thesis Supervisor: Ohyun Kwon

Chunghwi Yi: Thesis Committee Member #1

Heonseock Cynn: Thesis Committee Member #2

The Graduate School

Yonsei University

June 2013

Acknowledgements

Many people contributed to my academic growth in preparing this thesis.

First of all, I would like to express my profound appreciation to professor Oh−yun

Kwon for his help and support. He guided me in the research topic, and writing of my

thesis. Furthermore, he gave me various advices and encouragement including

enlightened me by saying “Always think.”

Additionally, I want to express my deep gratitude to professor Chung−hwi Yi for his

great teaching who has various academic experiences and enormous knowledge. I

would like to express my gratitude to professor Heon−seock Cynn for his kindness

and careful concern, giving me encouragement and intelligent advice. I also sincerely

thank professors, Hye−seon Jeon, Sung−hyun You, and Sang−hyun Cho, who helped

expand my knowledge and perspective.

I wish to thank sincerely my colleagues and friends, Kyue−nam Park, Sung−dae

Choung, Il−woo Park, and Min−sue Cho, who have given me encouragement for

better or worse. Thank all of your support. Also, I would like to thank all of the

members in the Graduate School Department of Physical Therapy. They have

provided me enormous mental support and assistance for my graduate course.

I deeply appreciate all of the therapists and professors of the Seoul National

University Bundang Hospital Department of Rehabilitation Medicine. They always

gave me the time to study, opportunity, and valuable support.

More than anybody, I wish to express my deep love and gratitude to all family who

always pray for me. My parents have provided endless love and mental support, and

wife’s parents have given me encouragement and careful concern. Especially my wife,

Yoo−jin and sons, Sung−june, and Hye−june have given me too much love and

affection. Without their belief in me and encouragement, I could never have finished

my graduate study.

Finally, I thank and praise God. I was able to finish my thesis with grace and

guidance by God. Thank you.

- i -

Table of Contents

List of Figures ······································································································· iii

List of Tables ········································································································ iv

Abstract ················································································································· v

Introduction ··········································································································· 1

Method ·················································································································· 5

1. Subjects ··········································································································· 5

2. Experimental Equipment ················································································· 6

2.1 Surface Electromyography ·········································································· 6

2.2 Electromagnetic Motion Tracking System ·················································· 6

2.3 Inclinometer ································································································ 6

3. Clinical Measurement ····················································································· 7

3.1 Tensor Fascia Latae Length Test With Inclinometer ·································· 7

4. Outcome Measurements ·················································································· 8

4.1 Muscle Activity ··························································································· 8

4.2 Kinematic Data Using Electromagnetic Motion Tracking System ············· 9

5. Tensor Fascia Latae Stretching Exercise ························································ 10

5.1 Active−Tensor Fascia Latae Stretching Exercise ······································· 10

5.2 Passive−Tensor Fascia Latae Stretching Exercise ······································ 10

6. Experimental Procedure ·················································································· 12

- ii -

7. Statistical Analysis ·························································································· 14

Results ··················································································································· 15

1. General Characteristics of the Subjects ··························································· 15

2. Muscle Activity ······························································································· 17

3. Hip Flexion and Internal Rotation Angle ························································ 21

4. Tensor Fascia Latae Muscle Length ······························································· 25

Discussion ············································································································· 27

Conclusion ············································································································ 32

References ············································································································· 33

Abstract in Korean ································································································ 40

- iii -

List of Figures

Figure 1. Active−Tensor Fascia Latae Stretching Exercise ·································· 11

Figure 2. Passive−Tensor Fascia Latae Stretching Exercise ································· 11

Figure 3. Active Side−Lying Hip Abduction ························································ 13

Figure 4. Gluteus Medius, Gluteus Maximus, and Tensor Fascia Latae Muscle

Activity ······························································································· 20

Figure 5. Hip Flexion and Internal Rotation Angle ·············································· 24

- iv -

List of Tables

Table 1. General Characteristics of Subjects ························································ 16

Table 2. Comparison of Gluteus Medius, Gluteus Maximus, and Tensor Fascia Latae

Muscle Activity Between Pre− and Post−Stretching Exercises ············ 18

Table 3. Comparison of Effects on Gluteus Medius, Gluteus Maximus, and Tensor

Fascia Latae Muscle Activity Between Passive− and Active−Tensor

Fascia Latea Stretching Groups ···························································· 19

Table 4. Comparison of Hip Flexion and Internal Rotation Angle Between Pre− and

Post−Stretching Exercises ····································································· 22

Table 5. Comparison of Effects on Hip Flexion and Internal Rotation Angle Between

Passive− and Active−Tensor Fascia Latae Stretching Exercise Groups

················································································································· 23

Table 6. Comparison of Tensor Fascia Latae Muscle Length Between Pre− and

Post−Stretching Exercises ····································································· 26

Table 7. Comparison of Effect on Tensor Fascia Latae Muscle Length Between

Passive− and Active−Tensor Fascia Latae Stretching Exercise Groups

················································································································· 26

- v -

ABSTRACT

Immediate Effect of Tensor Fascia Latae Stretching

Exercise on Muscle Activity and Hip Motion During

Active Side−lying Hip Abduction in Subjects With

Tensor Fascia Latae Shortness

Myungki Ji

Dept. of Physical Therapy

The Graduate School

Yonsei University

The purposes of this study were to investigate the effect of tensor fascia latae (TFL)

muscle stretching exercise on muscle activity and hip motion, and to compare the

effects of the passive− and active−TFL stretching exercise during active side−lying

hip abduction in subjects who have TFL shortness. Twenty subjects with TFL

shortness were recruited for this study and, using a random number table, were

randomly assigned to two groups: the passive−TFL stretching exercise group (PTS

- vi -

group) and the active−TFL stretching exercise group (ATS group). The subjects were

instructed how to perform PTS exercise or ATS exercise. Muscle activity of gluteus

medius (Gmed), gluteus maximus (Gmax), and TFL was measured with surface

electromyography (EMG), and electromagnetic motion tracking system was used to

measure the hip flexion and internal rotation angle during active side−lying hip

abduction. Measurement of TFL length is elicited by modified Ober test with

inclinometer. A paired t−test was utilized for determining the differences between

pre− and post−stretching exercise’s outcome (muscle activity of Gmed, Gmax, and

TFL, angle of hip flexion, and internal rotation, and TFL length). A comparison of the

effect of outcome measure of both groups was completed by an independent t−test.

The level of significance was set at α = 0.05. The results showed a significant

increase in Gmed muscle activity and significant decrease in hip flexion angle

between pre− and post−stretching exercise during active side−lying hip abduction.

Also, the results indicated that active−TFL stretching exercise significantly increased

the Gmax muscle activity than passive−TFL stretching exercise. It decreased the TFL

muscle activity, and decreased the hip flexion angle during active side−lying hip

abduction in subjects with TFL shortness. In conclusion, active−TFL stretching

exercise may be an effective method for modifying hip muscle activity and motion

during active side−lying hip abduction in people with TFL shortness.

Key Words: Active stretching, Passive stretching, Side−lying hip abduction, Tensor

fascia latae shortness.

- 1 -

Introduction

Hip abductor muscles play a major role in control of rotational alignment of the

limb (Fulkerson 2002; Lee 1999; Neumann 2002). The middle portion of the gluteus

medius (Gmed) muscle abducts the hip joint and the gluteus maximus (Gmax) muscle

is an extensor and an external rotator of the hip joint (Cutter, and KerVorkian 1999;

Neumann 2010). The superior portion of the Gmax also acts as a hip abductor during

gait (Lyons et al. 1983). The Gmed provides frontal plane stability for the pelvis

during walking and other functional activities (Earl 2004; Fredericson et al. 2000).

The Gmed has a more vertical pull and help initiate hip abduction, which is then

completed by the tensor fascia latae (TFL) (Gottschalk, Kourosh, and Leveau 1989).

The TFL muscle acts through the iliotibial band (ITB) by pulling it superiorly and

anteriorly (Gottschalk, Kourosh, and Leveau 1989). It assists in flexion, internal

rotation, and abduction of the hip (Fredericson et al. 2000; Travell, and Simons 1998).

Generally, one muscle dominates the movement pattern causing an imbalance to

occur, which may lead to injury (Jull, and Janda 1987; Page, Clare, and Robert 2010;

Sahrmann 2002). When muscle imbalance exists, some muscles are shortened and

other muscles are weakened (Jull, and Janda 1987; Page, Clare, and Robert 2010).

Muscle weakness is a common occurrence that arises in the synergistic muscles in the

hip. The TFL becomes short and the posterior fiber of the Gmed becomes weak

(Bewyer, and Bewyer 2003; Kendall et al. 2005). The imbalance of two synergistic

muscles contributes to compensatory joint motion and the development of movement

- 2 -

impairment (Sahrmann 2002). The weak Gmed is related to many injuries of the

lower extremities and abnormalities in the gait cycle (Kendall et al. 2005). The TFL

can become structurally short and mechanically incapable of lengthening to an

appropriate level and the weak Gmed can become structurally long and incapable of

shortening to an appropriate level (Comerford, and Mottram 2001; Kendall et al. 2005;

Sahrmann 2002). When muscles are incapable of firing correctly, compensation

occurs and this will alter joint motion and movement (Sahrmann 2002). Janda (1983)

have hypothesized a common muscle imbalance pattern in shortness of the TFL in

chronic musculoskeletal pain syndromes.

Assessments of movement are considered an important part of the physical

examination because movement may contribute to excessive stress and compression

on joints, and muscle, resulting in musculoskeletal pain and various injuries

(Sahrmann 2002). Janda (1983) suggested that in hip abduction movement pattern test,

the sign of an altered movement pattern is the tensor mechanism of hip abduction

facilitated by a short TFL. Instead of pure hip abduction in the plane of the trunk, the

movement is combined with hip flexion due to the TFL’s dual action as a hip flexor

and abductor (Page, Clare, and Robert 2010). Sahrmann (2002) suggested that lack of

posterolateral stabilization of the proximal femur is caused by impaired positioning

and overstretch of the muscles of the hip. This impaired movement is associated with

recruitment of TFL for hip abduction and flexion (Sahrmann 2002). Sahrmann (2002)

proposed that in lower quarter examination, the TFL is dominant when hip flexes and

- 3 -

the Gmed is weak when the hip is unable to tolerate during applying maximum

resistance in side−lying hip abduction with lateral rotation and extension.

It has been suggested that there are relative to a shortened TFL and a weak Gmed

with various lower extremity injuries and low back pain. Trendelenberg (1998) was

the first to describe a hip drop upon weight−bearing which indicated a Gmed

weakness in the gait, and concluded that lateral leg stability was solely maintained by

the tensile strength of the TFL. With a Trendelenburg gait, the pelvic drop occurs

when the Gmed doesn’t produce a sufficient internal hip abduction moment to

balance the external hip adduction moment that occurs during single leg stance (Earl

2004). Therefore, those with a Trendelenberg gait will have reduced gait efficiency

and be at greater risk of developing low back pain as a result of the pelvis not being

stabilized during the gait and other activities or when performing unilateral weight

training exercises (Bewyer, and Bewyer 2003; Earl 2004). Fredericson et al. (2000)

suggested that ITB syndrome may occur as a result of weakness of the Gmed, which

lead to decreased control of thigh abduction and external rotation. Fredericson et al.

(2000) hypothesized that this sequence of events places the ITB under increased

tension, making it more prone to impingement on the lateral epicondyle of the femur.

Earl (2004) described patellofemoral pain syndrome as an overuse injury. Inhibition

or dysfunction of the Gmed may contribute to decreased hip control, allowing greater

femoral internal rotation (Hertel, Sloss, and Earl 2005). This produces a larger valgus

vector at the knee, increasing the laterally directed forces acting on the patella (Earl

2004; Hertel, Sloss, and Earl 2005). Ober (1936) reviewed TFL shortness as a factor

- 4 -

in low back pain. Duchenne (1949) attributed that lower extremity changes from the

tough ITB contractures as femoral internal rotation, hip flexion contractures.

In previous studies, intervention methods to lengthen TFL and increase gluteal

muscle activity have been used. Fredericson et al. (2000) suggested that runners with

ITB syndrome have weaker hip abduction strength in the affected leg compared with

their unaffected leg. Through TFL−ITB self−stretching exercise, symptom

improvement with a successful return to the pre−injury training program parallels

improvement in hip abductor strength (Fredericson, and Wolf 2005). Tyler et al. (2006)

suggested that patients with patellofemoral pain syndrome have associated hip

weakness. Also, improvements in TFL−ITB flexibility were associated with excellent

results in patients with patellofemoral pain syndrome (Tyler et al. 2006).

Among previous studies related TFL stretching, hip muscle activity and hip motion

were not demonstrated in side−lying position. In addition, the comparison of passive−

and active−TFL stretching exercise on hip muscle activity and motion was not

established during active side−lying hip abduction in subjects with TFL shortness.

The purposes of this study were to investigate effect of TFL stretching exercise on

hip muscle activity and hip motion, and to compare effects of passive− and

active−TFL stretching exercise on muscle activity and hip motion during active

side−lying hip abduction in subjects with TFL shortness. The hypothesis of this study

was that the stretching exercise on TFL increases the muscle activity of Gmed, and

reduces angle of hip flexion and hip internal rotation during active side−lying hip

abduction in subjects with TFL shortness.

- 5 -

Method

1. Subjects

Twenty volunteers at the Yonsei University were recruited. The inclusion criteria for

subject selection in this study included that the shortness of TFL were a positive sign

by modified Ober test. Twenty subjects were randomly allocated into one of two

exercise groups: passive−TFL stretching exercise group, or active−TFL stretching

exercise group. Subjects with restricted passive range of motion of hip joint, history

of direct trauma or surgery to the lower extremity, diagnosis with disease in hip joint,

and significant weakness of Gmed, Gmax and TFL that interfere with hip abduction

were excluded (Arab et al. 2010). Prior to the study, the principal investigator

explained all procedures to the subjects, and all subjects signed an informed consent

form. This study was approved by Yonsei University Wonju institutional review board.

- 6 -

2. Experimental Equipment

2.1 Surface Electromyography

Muscle activity was measured using a Noraxon Telemyo 2400T (Noraxon, INC.,

Scottsdale, AZ, USA) with a pair of Ag−AgCl surface electrodes 2cm in diameter.

Raw electromyography (EMG) signals were band−pass sampled at 1000Hz, filtered

between 20 and 450Hz, and converted to root mean square using the MyoResearch

Master Edition 1.06 XP software (Noraxon, INC., Scottsdale, AZ, USA).

2.2 Electromagnetic Motion Tracking System

An electromagnetic motion tracking system (Liberty® Polhemus, Colchester, VT,

USA) was used to measure angle of hip flexion and internal rotation. This system

consists of a transmitter, receivers, digitizers and a system electronics unit.

2.3 Inclinometer

An inclinometer (Johnson Magnetic Angle Locator, Johnson, Mequon, WI, USA) is

a circular shape with a weighted needle that indicates the number of degrees on a

scale of a protractor. An inclinometer with markings at 1° increments was used for

the measurement of TFL length.

- 7 -

3. Clinical Measurement

3.1 Tensor Fascia Latae Length Test With Inclinometer

Measure of TFL length is elicited by modified Ober test with inclinometer. The

subjects were asked to lie laterally recumbent with the affected side uppermost. The

affected lower limb was then brought into full extension by the examiner, with some

abduction at the hip and the knee is extended. The examiner then slowly releases

support of the limb, allowing the limb to fall into adduction past the neutral position.

A short TFL restricts adduction and prevents the knee from falling past the neutral

position. An inclinometer was used during the modified Ober test to measure hip

adduction as an indication of TFL flexibility. Bandy et al. (2003) purposed that the

use of an inclinometer to measure hip adduction using the modified Ober test appears

to be a reliable method for the measurement of TFL length. During each measurement

session, subjects were positioned lying down with their tested side facing up. The

inclinometer was positioned at the popliteal fossa of the knee on the involved side

using the double sided tape to hold it securely in place, and hip adduction was

measured using the modified Ober test. If the limb was horizontal, it was considered

to be at 0 degrees, below horizontal (adducted) was recorded as a positive number,

and above horizontal (abducted) was recorded as a negative number (Bandy et al.

2003).

- 8 -

4. Outcome Measurements

4.1 Muscle Activity

Prior to electrode placement, the electrode sites were shaved and cleaned with

rubbing alcohol to prepare the skin. The electrode placement for the Gmax was

middle area in the line between greater trochanter and second sacrum spinous process

(S2). The electrode placement for Gmed was proximally 2cm area in the line between

iliac crest and greater trochanter of femur. The electrode on TFL was attached on the

2cm area below anterior superior iliac spine (ASIS).

Raw data was processed into the root−mean−square (RMS) with a moving window

of 50 milliseconds. For normalization, the mean RMS of three trials of 5−seconds

maximal voluntary isometric contraction (MVIC) was calculated for Gmed, Gmax

and TFL. The MVIC for the Gmax was tested such that hip extension was resisted

with the subject lying fully prone, with the knee flexed to 90°. The MVIC for the

Gmed was obtained during resisted hip abduction while subjects were lying in supine

position on the treatment table. Subjects exerted maximal abduction force against

resistance on the distal lateral leg, in a position of 30° of hip abduction, with the hip

and knee at 0° of flexion. The MVIC for the TFL was acquired in the same supine

position used for the Gmed, except that the hip was positioned in 45° between the

sagittal and coronal planes (Kendall et al. 2005).

- 9 -

4.2 Kinematic Data Using Electromagnetic Motion Tracking System

The receivers were mounted to thermoplastic frames and secured firmly to lower

third of the lateral thigh and over the first sacrum spinous process (S1) with double

sided tape. An anatomically relevant reference system for identifying the hip joint

centre was defined with a predicative method based on each subject’s pelvic and

lower limb anthropometrics (Bush, and Gutowski 2003). Using anatomically relevant

local coordinate axes derived from digitized bony landmarks data were reduced using

standard matrix transformations to determine the rotational matrix of the femur with

respect to the pelvis. Coronal plane motion was calculated as a composite angle

between hip and pelvis rotating about the sagittal axis of the pelvis. Transverse plane

motion was calculated as relative angle about the vertical axis (Bussey, Milosavljevic,

and Bell 2009). Thus, hip motion is described in three angles of movement in the

side−lying position; abduction (in the sagittal plane), flexion (in the transverse plane)

and rotation (in the coronal plane).

- 10 -

5. Tensor Fascia Latae Stretching Exercise

5.1 Active−Tensor Fasica Latae Stretching Exercise

Active−stretching exercise begins with the subject lying in prone position on the

treatment table. The subjects were asked to hip being positioned in rotation 0° and

adduction 0°, and flexed the knee 90°. The opposite hip was in the neutral rotation

and full knee extension. The subject slowly rotated the hip externally before

separating the ASIS of the pelvis in a direction to the upper side from the floor of the

table with pelvis hold to hand. This motion continues until the subject feels a stretch

on the side of the hip around the greater trochanter. The subjects were instructed to

maintain this position for 30 seconds and then rest for 30 seconds. The subjects were

asked to perform this exercise for 10 sets (Figure 1).

5.2 Passive−Tensor Fascia Latae Stretching Exercise

Passive−stretching exercise started in the same position as active stretching exercise.

The examiner conducted subjects to stretching exercise. The examiner executed the

exercise with his hand, holding pelvis with one hand and holding ankle with the other

hand. The examiner applied subjects to rotate the hip externally until the examiner

feels the end−feel. The examiner maintained this position for 30 seconds and the rest

for 30 seconds. This exercise completed 10 sets (Figure 2).

- 11 -

Figure 1. Active−Tensor Fascia Latae Stretching Exercise.

Figure 2. Passive−Tensor Fascia Latae Stretching Exercise.

- 12 -

6. Experimental Procedure

All subjects were evaluated for study inclusion/exclusion at the visit. The length of

each subject’s TFL was assessed by modified Ober test with inclinometer. The angle

of the hip motion and EMG data were collected during active hip abduction in

side−lying position. The subjects were asked to lie on the table in side−lying position

and the leg on the table was flexed to 45° at the hip and 90° at the knee. The subjects

were instructed to perform three times of active hip abduction extending knee (Figure

3). A target bar was placed to control the angle of the abducted hip. The target bar

was placed at 20° hip abduction position. The subject was asked to abduct their hip

until their ankle touched target bar and hold the position for 5−seconds. When the

subjects performed this motion, the examiner was not involved in any of the verbal

cue and touch. A large board was used to minimize the movement of pelvic, back,

and neck related to hip motion. The angle for hip was collected three times for the

tested side. The angle of the hip motion was measured using an electromagnetic

motion tracking system. EMG data were collected in three times by surface EMG and

were normalized by percent of MVIC. Subjects were allowed to rest for 1 minute

between trials. Following the pre−stretching exercise measurement, the subjects

received instruction in each TFL stretching exercise by a licensed physical therapist

with 7 years of clinical experience. All measurements were performed three times at

- 13 -

the time of entry into the study and at the direct time after each TFL stretching

exercise (pre− and post−stretching exercise).

Figure 3. Active Side−Lying Hip Abduction.

- 14 -

7. Statistical Analysis

The data are expressed as the means ± standard deviations. Statistical significance

between pre− and post−stretching exercise measurement was assessed through paired

t−test. This method was used to assess statistical significance of muscle activity of

Gmed, Gmax, and TFL, angle of hip flexion and internal rotation, and TFL length.

The independent t−tests were used to evaluate statistical significance of effects on

muscle activity for Gmed, Gmax, and TFL, angle of hip flexion and internal rotation,

and TFL length between passive− and active−stretching groups. The level of

statistical significance was set at p < 0.05. All statistical analysis was performed using

the statistical package for the Social Sciences for windows version 18.0 (SPSS, Inc.,

Chicago, IL, USA).

- 15 -

Results

1. General Characteristics of the Subjects

The general characteristics of the subjects including age, height, weight, body mass

index (BMI) are shown in Table 1. There were no significant differences in

parameters between passive−TFL stretching exercise group and active−TFL

stretching exercise group (p > 0.05).

- 16 -

Table 1. General characteristics of the subjects. (N=20)

Parameters

Passive−TFLa stretching

group (n1=10)

Active−TFL stretching

group (n2=10)

t p

Age (yrs) 23.4 ± 2.5b 23.3 ± 2.5 0.11 0.92

Height (cm) 174.2 ± 3.7 173.8 ± 5.4 0.19 0.85

Weight (kg) 67.8 ± 5.9 69.1 ± 7.1 -0.45 0.66

BMIc (kg/m2) 22.4 ± 2.2 22.9 ± 2.8 -0.51 0.61

aTFL: Tensor fascia latae. bMean ± standard deviation. cBMI: Body mass index. p value is comparison of groups using an independent t−test.

- 17 -

2. Muscle Activity

The muscle activity of the post−exercise Gmed was significantly greater than the

pre−exercise Gmed muscle activity (p<0.05). The post−exercise Gmax muscle

activity showed significantly greater activity when it was compared with the

pre−exercise Gmax in active−TFL stretching exercise group (p<0.05). The

post−exercise TFL muscle activity was significantly lower than the pre−exercise in

active−TFL stretching exercise group (p<0.05). However, there was no significant

difference in Gmax muscle activity between the pre− and post−stretching exercise in

passive−TFL stretching group (p>0.05). Also, there was no significant difference in

TFL muscle activity between the pre− and post−stretching exercise in passive−TFL

stretching group (p>0.05) (Table 2) (Figure 4).

There was significant difference in effects on Gmax or TFL muscle activity between

passive− and active−TFL stretching groups (p<0.05). However, there was no

significant difference in effect on Gmed muscle activity between passive− and

active− TFL stretching groups (p>0.05) (Table 3) (Figure 4).

- 18 -

Table 2. Comparison of gluteus medius, gluteus maximus, and tensor fascia latae

muscle activity between pre− and post−stretching exercises.

Muscle Group Stretching exercise

t p Pre Post

Gmeda PTSd 42.24 ± 12.52f 49.42 ± 15.17 -6.21 <0.01*

ATSe 48.38 ± 14.80 56.85 ± 14.79 -2.89 0.01*

Gmaxb PTS 50.50 ± 24.67 43.98 ± 14.63 1.53 0.15

ATS 32.61 ± 18.23 43.01 ± 16.66 -2.83 0.02*

TFLc PTS 25.77 ± 13.57 26.84 ± 13.29 -0.95 0.36

ATS 41.51 ± 18.70 30.40 ± 13.61 2.90 0.01*

aGmed: Gluteus medius. bGmax: Gluteus maximus. cTFL: Tensor fascia latae. dPTS: Passive tensor fascia latae stretching exercise. eATS: Active tensor fascia latae stretching exercise. fMean ± standard deviation. *p < 0.05, p value is comparison of pre− and post−stretching exercise using paired t−test.

- 19 -

Table 3. Comparison of effects on gluteus medius, gluteus maximus, and tensor fascia

latae muscle activity between passive− and active−tensor fascia latae stretching

groups.

Muscle

Group

t p

PTSd ATSe

Gmeda 7.17 ± 3.64f 8.46 ± 9.25 -0.40 0.68

Gmaxb -6.51 ± 13.39 10.40 ± 11.63 -3.01 0.01*

TFLc 1.07 ± 3.54 -11.11 ± 12.10 3.05 0.01*

aGmed: Gluteus medius. bGmax: Gluteus maximus. cTFL: Tensor fascia latae. dPTS: Passive tensor fascia latae stretching exercise. eATS: Active tensor fascia latae stretching exercise. fMean ± standard deviation. *p < 0.05, p value is comparison of passive− and active−stretching exercise using independent t-test.

- 20 -

Figure 4. Gluteus medius, gluteus maximus, and tensor fascia latae muscle activity.

prePTS: Pre−passive tensor fascia latae stretching exercise.

postPTS: Post−passive tensor fascia latae stretching exercise.

preATS: Pre−active tensor fascia latae stretching exercise.

postATS: Post−active tensor fascia latae stretching exercise.

Gmed: Gluteus medius.

Gmax: Gluteus maximus.

TFL: Tensor fascia latae.

*p<0.05: significant difference between pre−post test.

**p<0.05: significant mean difference between passive tensor fascia latae

stretching and active tensor fascia latae stretching exercise groups.

- 21 -

3. Hip Flexion and Internal Rotation Angle

The angle of post−exercise hip flexion was significantly lower than pre−exercise hip

flexion (p<0.05). The post−exercise internal rotation was significantly lower than

pre−exercise internal rotation in active−stretching group (p<0.05). However, there

was no significant difference in internal rotation angle between pre− and

post−stretching exercise in passive−stretching group (p>0.05) (Table 4) (Figure 5).

There was significant difference in effect on flexion angle between passive− and

active−stretching groups (p<0.05). However, there was no significant difference in

effect on internal rotation angle between passive− and active−stretching groups

(p>0.05) (Table 5) (Figure 5).

- 22 -

Table 4. Comparison of hip flexion and internal rotation angle between pre− and

post−stretching exercises.

Hip motion Group

Stretching exercise t p

Pre Post

Flexion PTSb 10.69 ± 4.70d 8.31 ± 4.51 3.25 0.01*

ATSc 14.16 ± 9.52 7.78 ± 9.59 6.12 <0.01*

IRa PTS 13.91 ± 5.01 12.70 ± 3.38 1.59 0.14

ATS 19.43 ± 9.23 12.63 ± 14.52 2.34 0.04*

aIR: Internal rotation. bPTS: Passive tensor fascia latae stretching exercise. cATS: Active tensor fascia latae stretching exercise. dMean ± standard deviation *p < 0.05, p value is comparison of pre− and post−stretching exercise using paired t−test.

- 23 -

Table 5. Comparison of effects on hip flexion and internal rotation angle between

passive− and active−tensor fascia latae stretching exercise groups.

Hip motion

Group

t p

PTSb ATSc

Flexion -2.38 ± 2.31d -6.68 ± 3.45 3.27 <0.01*

IRa -1.20 ± 2.38 -6.80 ± 9.16 1.87 0.08

aIR: Internal rotation. bPTS: Passive tensor fascia latae stretching exercise. cATS: Active tensor fascia latae stretching exercise. dMean ± standard deviation. *p < 0.05, p value is comparison of passive− and active−TFL stretching exercise using independent t−test.

- 24 -

Figure 5. Hip flexion and internal rotation angle.

prePTS: Pre−passive tensor fascia latae stretching exercise.

postPTS: Post−passive tensor fascia latae stretching exercise.

preATS: Pre−active tensor fascia latae stretching exercise.

postATS: Post−active tensor fascia latae stretching exercise.

IR: internal rotation.

*p<0.05: significant difference between pre−post test.

**p<0.05: significant mean difference between passive tensor fascia latae

stretching and active tensor fascia latae stretching exercise groups.

- 25 -

4. Tensor Fascia Latae Muscle Length

The TFL length of post−exercise was significantly greater than pre−exercise (p<0.05)

(Table 6). However, there was no significant difference in effect on TFL length

between passive− and active−TFL stretching groups (p>0.05) (Table 7).

- 26 -

Table 6. Comparison of tensor fascia latae muscle length between pre− and

post−stretching exercises.

Group Stretching exercise

t p Pre Post

TFLa length

(°)

PTSb -7.20 ± 2.39d -2.50 ± 2.27 -5.40 <0.01*

ATSc -7.00 ± 3.09 0.10 ± 4.28 -8.11 <0.01*

aTFL: Tensor fascia latae. bPTS: Passive tensor fascia latae stretching exercise. cATS: Active tensor fascia latae stretching exercise. dMean ± standard deviation. *p < 0.05, p value is comparison of pre− and post−stretching exercise using paired t−test.

Table 7. Comparison of effect on tensor fascia latae muscle length between passive−

and active−tensor fascia latae stretching exercise groups.

Group

t p

PTSb ATSc

TFLa length (°) 4.70 ± 2.75d 7.10 ± 2.76 -1.94 0.07

aTFL: Tensor fascia latae. bPTS: Passive tensor fascia latae stretching exercise. cATS: Active tensor fascia latae stretching exercise. dMean ± standard deviation. *p < 0.05, p value is comparison of passive− and active−TFL stretching exercise using independent t−test.

- 27 -

Discussion

The purposes of the present study were to investigate the effect of TFL stretching

exercise on hip muscle activity and hip motion in subject with TFL shortness, and

compare effects on muscle activity and hip motion between passive− and active−TFL

stretching exercises during active side−lying hip abduction.

The result showed that the muscle activity of the post−exercise Gmed was

significantly greater than the pre−exercise. Also, the muscle activity of the

post−exercise TFL was significantly lower than the pre−exercise in active−stretching

group. There are several possible explanations for lower muscle activity of TFL

during active side−lying hip abduction. First of all, mechanical factors involving the

viscoelastic properties of the muscle may affect the muscle’s length-tension

relationship. Previous studies (Kokkonen, Nelson, and Cornwell 1998; Nelson, and

Kokkonen 2001) have suggested that the primary mechanism underlying the

stretching induced decreases in force may alter the muscle length−tension relationship.

Secondly, it has also been hypothesized that neural factors contribute to the

stretching−induced decrease in force. A number of peripheral mechanisms have been

proposed to explain the reduced muscle activation after stretching (Avela et al. 1999;

Behm, Button, and Butt 2001; Fowles, Sale, and MacDougall 2000). The peripheral

mechanism includes the autogenic inhibition of the Golgi tendon reflex,

mechanoreceptor and nociceptor afferent inhibition, joint pressure feedback inhibition

- 28 -

due to excessive ranges of motion during stretching, and stretching reflex inhibition

originating from the muscle spindle. Additionally, Avela et al. (1999) suggested that a

central nervous system mechanism may be responsible for the decreases in muscle

activation.

The increase in Gmed activation and decrease in TFL following the stretching

exercise was contrary with the original hypothesis that their activation would

respectively reduce and increase in subject with TFL shortness (Fredericson, and Weir

2006). Some investigators have also hypothesized a common muscle imbalance

pattern of weakness in hip abductor and shortness of TFL (Sahrmann 2002;

Comerford, and Mottram 2001). It is assumed that when the primary muscle

responsible for hip abduction; gluteus medius, is weakened, the synergistic muscle;

TFL, is substituted and becomes overactive to be the primary muscle (Sahrmann 2002;

Comerford, and Mottram 2001). Hence, in theory, it is thought that hip abductor

increase is accompanied with TFL decrease in these subjects. Finally, this study

suggests that the TFL stretching exercise affect increase of Gmed activation and

decrease of TFL muscle activity during active side−lying hip abduction in subjects

with TFL shortness.

The results of this study indicate that hip flexion is significantly decreased during

active side−lying hip abduction following stretching exercises. Also, the angle of the

post−exercise internal rotation was significantly lower than the pre−exercise in

active−stretching exercise group. There are numerous possible reasons for these

results. Firstly, although the Gmed and TFL are both hip abductors, the Gmed,

- 29 -

especially the posterior fiber of Gmed is an external rotator of the hip and TFL is an

internal rotator and a flexor of hip. Thus, the function of hip abductor muscle

following the stretching exercise could not be completely substituted by TFL, but the

function of hip abductor muscle could be acted by Gmed. In the second place, it is

assumed that when primary muscle responsible for a specific joint movement is

weakened, the synergistic muscle is substituted and becomes overactive to be the

primary muscle responsible for the movement (Sahrmann 2002). Based on this

hypothesis, it is speculated that TFL shortness is a compensatory mechanism.

Accordingly, TFL stretching exercise allows the subjects with TFL shortness to be

responsible for the activation of the primary muscle: Gmed, during the hip abduction.

Therefore, this study recommended that TFL stretching exercise affects decrease of

hip flexion and internal rotation angle during active side−lying hip abduction in

subjects with TFL shortness.

Hip flexion angle between pre− and post−stretching exercise differences were -2.38

± 2.31 in passive−TFL stretching exercise group and -6.68 ± 3.45 in active−TFL

stretching exercise group. Our results indicate that the active−TFL stretching exercise

decreased the hip flexion angle significantly more than the passive−TFL stretching

exercise during active side−lying hip abduction. Also, the differences of Gmax and

TFL muscle activity between pre− and post−stretching exercise were -6.51 ± 13.39

and 1.07 ± 3.54 in passive−TFL stretching exercise group, and 10.40 ± 11.63 and -

11.11 ± 12.10 in active−TFL stretching exercise group, respectively. The results

indicate that the active−TFL stretching exercise increased the muscle activity of

- 30 -

Gmax and decreased TFL muscle activity significantly more than the passive−TFL

stretching exercise during active side−lying hip abduction. Nonetheless, there was no

significant difference in effects of TFL stretching exercise on hip internal rotation

angle, the muscle activity of Gmed, and TFL length between passive− and

active−stretching exercise groups. Previous studies (Medeiros et al. 1977; Tanigawa

1972; Taylor et al. 1990) proposed that improvements made by patients using passive

stretching may be the result of both autogenic inhibition and tensile stress applied to

the muscle according to muscles’ viscoelastic characteristics; when stress is applied

over a constant period of time, the muscle will gradually relax and increase in length.

With autogenic inhibition, the muscle being stretched is inhibited and is thought to

simultaneously relax. Active stretching also places a tensile stress on the muscle

being stretched, but additional increases in length are thought to be achieved through

relaxation via reciprocal inhibition (Kandel, Schwartz, and Jessell 2000). Although

the neurologic mechanisms of muscle relaxation in active and passive stretching are

thought to be different, tensile stress is common to both types of stretching and is

probably the primary factor for increasing muscle flexibility. This could explain

various results about this topic. White, and Sahrmann (1994) suggested that active

stretching increase the flexibility of the tight muscles while concomitantly improving

function of the antagonistic muscles. This study assessed the effect of stretching type

on the function of the antagonist muscles. There are significant differences in effects

on Gmax muscle activity between passive− and active−stretching exercises.

Consequently, present study suggests that active−stretching exercise was more

- 31 -

effective than passive−stretching exercise on Gmax and TFL muscle activity, and hip

flexion angle during active side−lying hip abduction in people with TFL shortness.

Both post−exercise showed a significantly greater increase in the length of TFL than

pre−exercise. The present study showed that TFL stretching exercise lengthened the

TFL muscle. Our results are consistent with those of a previous study showing that

stretching TFL is an effective method for increasing TFL length (Fredericson et al.

2002). Therefore, this study suggests that TFL stretching exercise in this study was

effective method for elongating the TFL.

The present study has several limitations. First of all, we did not directly measure

the length of TFL muscle. Besides, we studied the effect of the TFL stretching

exercise, and it is not clear whether our results can be generalized to other functional

activities in subjects with TFL shortness. In addition, generalization of the study is

limited because a small number of subjects participated and our subjects were young.

Finally, the stretching exercise was a short−term intervention. Further studies are

needed to determine the long−term effect of TFL stretching on hip motion and muscle

activity during active side−lying hip abduction in more subjects than present subjects

with TFL shortness.

- 32 -

Conclusion

The present study investigated the effect of the TFL stretching exercise on hip

muscle activity and motion, and compared the effect of the passive− and

active−stretching exercise during active side−lying hip abduction in subjects with

TFL shortness. The findings of this study showed significant increase in Gmed

muscle activity and significant decrease in hip flexion angle between pre− and

post−stretching exercise during active side−lying hip abduction. The results indicate

that active−stretching exercise is compared with passive−stretching exercise

significantly increased the Gmax muscle activity, decreased the TFL muscle activity,

and decreased the hip flexion angle during active side−lying hip abduction in subjects

with TFL shortness. In conclusion, active−TFL stretching exercise may be an

effective method for modifying hip muscle activity and motion during active

side−lying hip abduction in people with TFL shortness. In its final analysis, the

findings of the present study provide evidence for the effectiveness of TFL stretching

in subjects with TFL shortness.

- 33 -

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- 40 -

국문 요약

넙다리근막긴장근 단축 대상자에게 신장운동이

근활성도와 엉덩관절 움직임에 미치는 즉각적인 영향

연세대학교 대학원

물리치료학과

지 명 기

본 연구의 목적은 넙다리근막긴장근이 단축된 대상자에게 수동적 넙다리

근막긴장근 신장운동과 능동적 넙다리근막긴장근 신장운동을 시킨 후 옆으

로 누운 자세에서 엉덩관절 벌림 시 근활성도와 엉덩관절 움직임에 미치는

영향을 알아보고 수동적 신장운동과 능동적 신장운동의 효과를 비교하는

것이다. 본 연구를 위해 넙다리근막긴장근이 단축된 20명의 대상자가 참

여하였고, 수동적 넙다리근막긴장근 신장운동 집단과 능동적 넙다리근막긴

장근 신장운동 집단에 난수표를 이용하여 무작위로 할당하였다. 각각의 대

상자들은 수동적 신장운동이나 능동적 신장운동 수행 방법을 교육받았다.

- 41 -

중간볼기근, 큰볼기근, 그리고 넙다리근막긴장근의 근활성도는 표면 근전

도 장비를 사용하여 측정하였고 전자기 움직임 추적 시스템은 옆으로 누워

엉덩관절 벌림 시 엉덩관절의 굽힘과 안쪽 돌림 각도를 측정하는데 사용하

였다. 중간볼기근, 큰볼기근과 넙다리근막긴장근의 근활성도, 엉덩관절 굽

힘과 안쪽 돌림의 각도, 그리고 넙다리근막긴장근의 길이에 대한 신장운동

전과 후 간 차이를 알아보기 위해 짝비교 t−검정을 하였다. 수동적 신장운

동 집단과 능동적 신장운동 집단 간의 차이가 있는지를 알아보기 위해 독

립 t−검정을 하였다. 통계학적 유의수준 α = 0.05로 하였다. 연구 결과

옆으로 누워 엉덩관절 벌림 시 신장운동 전과 후 중간볼기근의 근활성도는

유의하게 증가하였으며, 엉덩관절 굽힘 각도는 유의하게 줄어들었다. 또한,

수동적 넙다리근막긴장근 신장운동과 비교하여 능동적 넙다리근막긴장근

신장운동이 넙다리근막긴장근이 단축된 대상자가 옆으로 누워 엉덩관절을

벌림 시 유의하게 큰볼기근의 근활성도는 증가하였고 넙다리근막긴장근의

근활성도는 감소하였으며, 엉덩관절 굽힘 각도는 유의하게 감소하였다. 결

론적으로, 능동적 넙다리근막긴장근 신장운동이 넙다리근막긴장근이 단축

된 사람들이 옆으로 누워 엉덩관절을 벌림 시 엉덩관절 근활성도와 움직임

을 교정하는데 효과적인 중재방법으로 사료된다.

핵심 되는 말: 넙다리근막긴장근 단축, 능동적 신장, 수동적 신장, 옆으로

누워 엉덩관절 벌림.