Relationship Between Mechanical Factors

Relationship Between Mechanical Factorsand Incidence of Low Back PainMohammad Reza Nourbakhsh, PT, PhD1

Amir Massoud Arab, PT, MSc2

Study Design: A multifactorial cross-sectional nonexperimental design.Objectives: To collectively investigate the association among 17 mechanical factors andoccurrence of low back pain (LBP).Background: Several physical characteristics, based on assumptions, clinical findings, andscientific experiments, have been associated with the development of LBP. Controversy existsregarding the degree of association between some of these physical characteristics and LBP.Information regarding the degree of association of each factor to LBP is needed for effectiveprevention and appropriate treatment strategies.Methods and Measures: A total of 600 subjects participated in this study. Subjects werecategorized into 4 groups: asymptomatic men (n = 150, age [mean SD] = 43 15 years),asymptomatic women (n = 150, age [mean SD] = 43 13 years), men with LBP (n = 150, age[mean SD] = 43 14 years), and women with LBP (n = 150, age [mean SD] = 43 13years). Seventeen physical characteristics were measured in each group and the relativeassociation of each characteristic with LBP was assessed.Results: Among all the factors tested, endurance of the back extensor muscles had the highestassociation with LBP. Other factors such as the length of the back extensor muscles, and thestrength of the hip flexor, hip adductor, and abdominal muscles also had a significant associationwith LBP.Conclusion: It appears that muscle endurance and weakness are associated with LBP and thatstructural factors such as the size of the lumbar lordosis, pelvic tilt, leg length discrepancy, and thelength of abdominal, hamstring, and iliopsoas muscles are not associated with the occurrence ofLBP. J Orthop Sports Phys Ther 2002;32:447460.

Key Words: back extensor endurance, low back pain, lumbar lordosis,muscle length, muscle strength

Low back pain (LBP) is one of the most frequent health-related complaints in western societies.110 Previous studieshave indicated that 70% to 80% of the western populationhave had at least 1 episode of LBP in their lifetime.110,120Despite its detrimental association with social and work-related activities, the exact cause of mechanical LBP has not yet beendetermined. Several factors, based on assumptions, clinical findings,and scientific experiments, have been associated with the developmentof LBP. However, with the use of different designs and testing proce-dures, controversial results have been reported in the literature.

1 Assistant professor, University of Social Welfare and Rehabilitation Sciences, Tehran, Iran.2 Physical therapist, University of Social Welfare and Rehabilitation Sciences, Tehran, Iran.This study was partially supported by the University of Social Welfare and Rehabilitation Sciences andapproved by the Human Subject Committee of the University of Social Welfare and RehabilitationSciences, Tehran, Iran.Send correspondence to Mohammad Reza Nourbakhsh, Dr. Chamran Highway, 5th (Kaj) Street Number30, Tehran 14417, Iran. E-mail: [email protected]

Lumbar Lordosis

Two major theories have longspeculated that changes in the sizeof the lumbar lordosis are themain cause of LBP.82,123 Will-iams123 attributed LBP to the in-creased lumbar lordosis resultingfrom abdominal muscle weaknessdue to prolonged sitting posture.In contrast, Mckenzie82 attributedLBP to decreased lumbar lordosisand posterior displacement of thenucleus pulposus of theintervertebral disc in the lumbarspine. To validate these assump-tions, the effects of lumbar flexionand extension exercises on LBPhave been studied. Flexion exer-cises, which are assumed to de-crease lumbar lordosis, have beenfound to have the same effect onreducing LBP as extension exer-cises, which are expected to in-crease the lumbarcurve.16,29,32,40,78,127 This issue hasbeen further investigated, and norelationship has been found be-tween the size of lumbar lordosisand development ofLBP.27,30,37,41,87,96,124 These find-ings have led to questions regard-ing the rationale behind these twomajor theories and the subsequenttreatment programs.

Pelvic Tilt

Based on the anatomic relation-ship between the pelvis and thelumbar spine, it has been specu-lated that changes in the pelvicinclination affect the size of the

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lumbar lordosis and cause LBP.1,18,26,65,67 Both ofthese assumptions have been challenged. Some stud-ies demonstrated that there was no correlation be-tween the angle of pelvic inclination and the size ofthe lumbar lordosis.6,116,121,124 Although Roncaratiand McMullen99 found that there was an increasedanterior pelvic tilt in patients with LBP, others havenot found a significant difference in the angle ofpelvic inclination among asymptomatic subjects andsubjects with LBP.21,27,30

Abdominal Muscle Length and Strength

Based on the anatomic position and function ofthe abdominal muscles, it has been speculated thatabdominal muscle weakness produces an anteriorpelvic tilt and lumbar hyperlordosis, resulting inLBP.1,18,26,61,65,67 In addition, several studies havefound decreased abdominal muscle strength in pa-tients with LBP.3,46,73,83,88 In contrast to these find-ings, some investigators have found that there is noassociation between the angle of pelvic inclination,the size of the lumbar lordosis, and abdominalmuscle strength.75,121,124 Moreover, other studieshave shown no significant difference in abdominalmuscle strength between asymptomatic individualsand those with LBP.5,74,106,113 Finally, some reportshave demonstrated that no association exists betweenthe length of the abdominal muscles and the size ofthe lumbar lordosis.116,124

Back Extensor Muscle Endurance

Back extensor muscles are considered posturalmuscles that aid in maintaining upright standing pos-ture and controlling lumbar forward bending.18 Sev-eral studies have reported a significant decrease inback extensor muscle endurance in patients withLBP.3,8,18,19,51,58,101 It is thought that decreased backmuscle endurance causes muscular fatigue and over-loads soft tissue and passive structures of the lumbarspine, resulting in LBP.79,122

Back Extensor Muscle Flexibility

According to Williams theory of LBP, prolongedsitting causes back extensor muscle tightness, which,in turn, overstresses the lumbar spine, resulting inLBP.65,123 Janda54 and Jull and Janda61 classify backextensors as postural muscles, which have a tendencyto shorten with overstress and back pain. Other in-vestigators have also shown decreased flexibility andback muscle tightness in patients with LBP.14,52,70,117

Some studies, however, have found no difference inthe flexibility of back extensor muscles in athleteswith and without LBP,3,119 which may be due to en-hanced general flexibility in the athletic population.

Iliopsoas Muscle Length

Some studies have shown decreased iliopsoasmuscle length3,84 and strength73 in patients with LBP.Because the iliopsoas muscle attaches to the pelvisand lumbar spine, some have assumed that tightnessof this muscle causes increased lumbar lordosis andthat weakness of this muscle causes decreased lumbarlordosis, which, in turn, can result in LBP.18,67,105

Recent studies have found no association betweenthe length of the iliopsoas muscle and the size of thelumbar lordosis,116,124 between the size of the lumbarcurve and LBP,27,30,37,41,87,96,124 or between tightiliopsoas muscle and LBP.45

Hamstrings Muscle Length

Hamstrings tightness is one of the most commonfindings in patients with LBP.1,18,52,54,61,65,84,105 It isthought that, due to the attachments of hamstringsto the ischial tuberosity, hamstrings tightness gener-ates posterior pelvic tilt and decreases lumbarlordosis, which can result in LBP.1,18,65,84,105 Hells-ing,45 however, examined 600 young men and con-cluded that no association existed between ham-strings tightness and LBP. Van Wingerden et al118

suggested that hamstrings tightness in patients withLBP is a compensatory mechanism secondary to pel-vic instability.

Leg Length Discrepancy

Several studies have shown the presence of leglength discrepancy in patients with LBP.43,99,111 Leglength inequality is thought to cause LBP by generat-ing a lateral pelvic inclination and lumbarscoliosis.33,81 Schaffer105 believes that leg length dis-crepancy causes anterior innominate rotation on theside of the shorter leg and posterior innominate ro-tation on the side of the longer leg. Innominate ro-tation is thought to cause sacral tilt, affecting thelumbosacral articulation. Hoikka et al,49 however,support neither of the above hypotheses. Theyshowed that leg length discrepancy had a moderatecorrelation with sacral tilt, and a poor correlationwith lumbar scoliosis. Others have also questionedthe association between leg length inequality andLBP.21,39,107,126

Iliotibial Band Tightness

Stretching of the iliotibial band is frequently rec-ommended in treatment programs for patients withLBP.71 Because the iliotibial band attaches to theilium, tightness of this muscle is thought to causeanterior innominate rotation and lateral pelvictilt.61,105 We found no study that has directly evalu-ated the effect of tightness of the iliotibial band onLBP.

448 J Orthop Sports Phys Ther Volume 32 Number 9 September 2002

Foot Pronation

The relationship between subtalar joint pronationand LBP has been previously reported in some casestudies.12,23 It is suggested that excessive foot prona-tion may produce lower-extremity medial rota-tion,11,90 functional leg length disparity,11,25 and pel-vic obliquity.11,100 Increased pelvic obliquity, assuggested by Botte,11 creates lateral deviation and afunctional scoliosis of the lumbar spine. Unilateralleg shortening and excessive medial rotation of thelimb is thought to produce anterior pelvic tilt11,104

and increased lumbar lordosis.11 These structuralimbalances caused by unilateral foot pronation pre-sumably result in LBP in some patients.11,12,23 Fur-ther research is indicated to determine the signifi-cance of foot pronation in the development of LBP.

Hip Abductor and Adductor Muscle Flexibility andStrength

Hip abductor and adductor muscles play a signifi-cant role in pelvic lateral stability.71 Any imbalance inthe function of these muscles due to muscle shorten-ing or weakness may cause pelvic obliquity and func-tional lumbar lateral bending.65 Vertebral rotationcoupled with vertebral lateral bending may overstresslumbar soft tissue and facet joints.105 Furthermore,considering the role of these muscles in sacroiliacjoint stability,71 any disturbance in their function canlead to sacroiliac joint instability and LBP. However,the effect of weakness or shortening of these muscleson LBP has not been directly assessed.

Triceps Surae Muscle Flexibility

Calf muscles are classified as postural muscles,which, according to Jull and Janda,61 have a ten-dency to shorten in reaction to physical stress or in-jury. Triceps surae muscle tightness can cause footpronation31 and leg length discrepancy (flexedknee). Both of these conditions, as discussed previ-

ously, can lead to LBP. However, the significance ofcalf muscle tightness in the development of LBP hasnot been determined.

Objectives

As noted above, controversy exists regarding theassociation between various physical characteristicsand the occurrence of LBP. In addition, the associa-tion between several other physical characteristicsand LBP has not yet been scientifically examined.Most previous studies have considered only a fewphysical characteristics and have been performed ona relatively small population. Furthermore, the fac-tors that have the greatest association with the inci-dence of LBP have not yet been identified. Thisstudy collectively investigates the association betweenseveral characteristics and LBP in a large populationand identifies the relative association of each factorwith LBP.

METHODS

Subjects

A total of 600 subjects between the ages of 20 and65 were randomly recruited from 5 hospitals inTehran, Iran. Subjects were categorized into 4groups: asymptomatic men (n = 150, age [mean SD] = 43 15 years), asymptomatic women (n = 150,age [mean SD] = 43 13 years), men with LBP(n = 150, age [mean SD] = 43 14 years), andwomen with LBP (n = 150, age [mean SD] = 43 13 years). To account for the effect of age on theconsidered variables, the subjects in each group werefurther divided into 3 age ranges (ages 2035, 3650,and 5165 years). Subjects were recruited so that anequal number of individuals (n = 50) in each agerange were allocated to each group. The mean age,height, and mass of the subjects in each group areshown in Table 1.

TABLE 1. Age (mean SD), height, and mass of asymptomatic subjects and those with low back pain.

Men Women

Variables Asymptomatic Low Back Pain Asymptomatic Low Back Pain

Age 2035 (y)* 26 4 27 5 28 4 28 4Age 3650 (y)* 42 4 41 4 43 4 43 5Age 5165 (y)* 61 5 60 5 58 5 58 4Height (cm) 170 6 172 7 166 7 160 6Mass (kg) 72 11 74 11 66 11 68 10

* n = 50 per group. n = 150 per group.

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Selection Criteria

Subjects (symptomatic and asymptomatic) wereincluded if they had no history of spinal surgery, nospinal or pelvic fracture, no history of hospitalizationfor severe trauma or injuries from a car accident, nohistory of osteoarthritis or fracture of the lower ex-tremities, and no history of any systemic disease,such as arthritis or tuberculosis. Asymptomatic sub-jects were selected among those who either accompa-nied a patient or were referred to the hospital fornonmusculoskeletal problems. These subjects wereevaluated and found to have no complaint of anypain or dysfunction in their lower extremities, lowback, thoracic and neck areas. Patients were includedif they had a history of LBP for more than 6 weeksbefore the study or had on-and-off back pain andhad experienced at least 3 episodes of LBP, each last-ing more than 1 week during the year before thestudy. None of the subjects with or without LBP hadreferred leg pain. Individuals with leg pain were ex-cluded from the study. Sixty-eight percent (n = 204)of the patients had LBP for more than 6 months andcomplained of pain and stiffness in the lower back atthe time of the study. Before participating in thestudy, all subjects signed an informed consent formapproved by the University of Social Welfare and Re-habilitation Sciences Human Subjects Committee.

Reliability Assessment

Intratester reliability of the measurements was as-sessed using 20 men and 20 women asymptomaticvolunteers. Except for the measurements of endur-ance of the back extensor muscles, foot arch height,and the strength of the abdominal, hip flexor, hipextensor, hip abductor and hip adductor muscles,the rest of the variables were tested by 2 examinersto establish intertester reliability. The first examinercompleted the tests on a subject and after 15 min-utes repeated the tests in a random order on thesame subject. The second examiner then tested thesubject following the same procedure.

Procedures

Several variables were measured in this study. Adescription of the procedure and instruments usedto measure each variable is as follows.

Size of Lumbar Lordosis A standard flexible ruler wasused to measure the size of the lumbar lordosis inthe standing position based on the method ex-plained by Youdas et al.124,125

Angle of Pelvic Tilt An inclinometer manufacturedin our laboratory was used to measure the angle ofpelvic tilt (Figure 1). This instrument was composedof a 360 scaled dial mounted on a horizontal bar.Two adjustable moving pointers were placed at eachend of the bar. A plumb line was suspended from

FIGURE 1. Inclinometer used to measure pelvic tilt. (A, plumb lineindicates 0 when the inclinometer is parallel to the ground; B,plumb line shows the tilting angle of the inclinometer.)

the center of the dial. When the horizontal bar washeld parallel to the ground, the position of theplumb line on the dial would indicate the 0 angle(Figure 1A). When the inclinometer was tilted, theposition of the plumb line would show the angle oftilt (Figure 1B). The inclinometer was calibrated andhad 98% measurement accuracy. To measure theangle of pelvic tilt in standing posture, one of thepointers was placed over the anterior superior iliacspine (ASIS) and the other was placed over the pos-terior superior iliac spine (PSIS). The angle betweenthe two landmarks, as indicated on the scaled dial,was considered to be the angle of pelvictilt.13,75,116,121,124

Length of Abdominal Muscles Previous studies haveused the prone press-up maneuver to estimate thelength of the abdominal muscles.14,114,116,124 Withthis procedure, it is assumed that the abdominalmuscles are lengthened in a direction opposite totheir action.124 We hypothesized that limited lumbarextension due to bony contact between the spinousprocesses,64 in addition to pain and stiffness, mightlimit full abdominal muscle lengthening. In thisstudy, the length of the abdominal muscles was esti-mated by measuring the distance between thexiphoid and the symphysis pubis in erect standingposture. The value obtained was normalized by divid-ing it by the length of the subjects trunk, measuredas the distance from the top of the head to the levelof the second sacral vertebra (S2). It was assumed

A

B

0

0


that the pressure from the internal organs in relaxedstanding position would stretch the abdominalmuscles to their resting length.

Length of Low Back Extensor Muscles The degree ofmaximum lumbar flexion was used as an indicator ofthe length of the back extensor muscles.15,114,124,125

A flexible ruler was used and the procedure de-scribed by Youdas et al125 to measure the subjectsmaximum lumbar flexion in the sitting position wasfollowed. The quantitative method described by oth-ers15,125 was used to obtain the amount of maximumlumbar flexion in degrees.

Length of Hip Flexor Muscles The length of the hipflexor muscles was assessed indirectly based on theThomas test described by Kendall65 and Magee.77

The detailed instructions provided by Youdas et al124

to measure the angle between the longitudinal axesof the trunk and the thigh of subjects on theipsilateral side to that of the assessed muscles werefollowed. Angles that measured less than 180 indi-cated the level of tightness in the hip flexor muscles.The average of the measurements obtained from theright and left side was recorded as the length of thehip flexor muscles.

Length of Hamstring Muscles In this study, the activeknee extension test described by Gajdosik et al36 wasused to measure the length of the hamstringmuscles. Others have used the straight leg-raising(SLR) test to assess the length of thesemuscles.34,35,50,84,116 Bohannon,10 however, arguesthat, due to pelvic rotation with the SLR test, it maynot be an accurate means to measure the length ofthe hamstring muscles. The average of the measure-ments obtained from the right and left side was re-corded as the length of the hamstring muscles.

Length of Hip Adductor Muscles Measurement of pas-sive hip abduction was used to estimate the length ofthe hip adductor muscles. The subject was instructedto lie supine on a treatment table with the hips andknees straight and arms folded across the chest. Thecenter of a goniometer was placed over thesymphysis pubis while one examiner, palpating theASIS, monitored pelvic motion, and the other exam-iner slowly moved the subjects leg into hip abduc-tion just to the point before the pelvis started tomove. The angle between the body midline and thelongitudinal axis of the femur of the tested leg, mea-sured in degrees, represented the indirect length ofthe hip adductor muscles. The subjects leg wasbrought back to the starting position, and the proce-dure was repeated for the other leg. The average ofthe measurements obtained from the right and leftside was recorded as the length of the hip adductormuscles.

Endurance of Erector Spinae Muscles Erector spinaeendurance was assessed with the subject lying proneon a treatment table with the hands laying beside hisor her trunk. The subject was instructed to lift the

upper trunk exactly 30 from the table and to holdthis position for as long as possible. The detailedprocedure for this test is described by Ashmen et al.3

The length of time, measured in seconds by a stop-watch, that subjects could hold this designated anglewas considered to be the measure of erector spinaeendurance (Figure 2). At the end of the test proce-dure, the subjects were asked if pain was a limitingfactor to maintain the position longer. The subjectswho had pain during the testing procedure were ex-cluded from the study.

Length of the Gastrocnemius Muscles The passivedorsiflexion test, previously described by Johnsonand Gross,57 was used to assess the flexibility of thegastrocnemius muscles. The average of the measure-ments obtained from the right and left side was re-corded as the length of the gastrocnemius muscles.

Length of the Iliotibial Band The Ober test was per-formed to assess tightness in the iliotibial band.31,77

This test was performed in the side lying position.The subjects lower leg was flexed at the hip andknee joints. The examiner, standing behind the sub-ject, stabilized the pelvis with one hand, and with theother hand passively abducted and extended the hipwith the knee flexed. Maintaining extension andneutral position of the subjects hip, the examinerallowed the testing leg to drop toward the table. Ifthe subjects leg remained abducted, the subject wasconsidered to have iliotibial band tightness.77 Noquantitative measures were taken, and, based on testresults, subjects were categorized as with or withoutiliotibial band tightness.

Leg Length Discrepancy The length of each lowerextremity was measured with the subject lying supineon a treatment table. The reference leg length wasmeasured from the ASIS to the distal medial mal-leolus with a measuring tape.21,55,57,62,69 Leg length

FIGURE 2. Procedure for measuring the back extensor muscleendurance. The subject is lying prone on a treatment table with thehands lying beside his/her trunk. The subject was instructed to liftthe upper trunk exactly 30 from the table and hold this position foras long as possible.


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differences greater than 10 mm were considered ab-normal,38,99 and subjects were categorized as with orwithout leg length disparity.

Foot Arch The configuration of the longitudinalarch of the foot was used to determine foot prona-tion in subjects.22 The subject was instructed to standon water-soaked foam to wet the soles of the feet. Animpression was then made by asking the subject tostep on a block of wood with weight evenly distrib-uted on both feet. The index proposed by Staheli etal,109 the ratio of the width of the foot in the archarea to the width of the heel, was used to determinethe level of foot pronation in subjects. The averageof the measurements obtained from the right andleft side was recorded as the index of foot arch.

Testing Muscle Strength To measure muscle strengthin an objective and quantitative fashion, a pressuremeter similar to the one described by Helewa et al43

was used (Figure 3A). The reliability and validity ofusing pressure meters for measuring muscle strengthhas previously been established.42 The unit used inthis study was calibrated and had 99% linearity.

Muscle strength was assessed for the hip flexors,hip extensors, hip abductors, hip adductors, and ab-dominal muscles. Test methods were similar to thosedescribed for manual muscle testing of the abovemuscles,65 except that the inflated bag of the pres-sure meter was placed between the examiners handand the specified contact point on the subjectslimbs or trunk (Figure 3B). Helewa et al44 providedetailed instructions for using pressure meters to as-sess abdominal and hip flexor muscle strength. Atthe end of the test procedure, the subjects wereasked if their ability to perform the test was limiteddue to pain or lack of strength. If pain was a limitingfactor for a subject to produce maximum muscleforce, that subject was excluded from the study. Theaverage of the measurements obtained from theright and left side was recorded as the strength ofthe hip flexor, hip extensor, hip abductor and hipadductor muscles.

Data Analysis

We used an intraclass correlation coefficient (ICC)and 2-way mixed-effect model108 to assess intertesterand intratester reliability of the measurements. APearson correlation coefficient was used to assess cor-relation between the variables of the study. We testedquantitative data by using 2 2 ANOVA, accountingfor sex, health status (symptomatic versusasymptomatic), and interaction of health status andsex effects. We used pooled data where there was nosignificant health-status-by-sex interaction effect, butanalyzed the data separately for men and women forthe variables which had a significant health-status-by-sex interaction. Categorical data (iliotibial bandlength, and leg length discrepancy) were assessed by

FIGURE 3. The pressure meter (A) and the method of use (B) toassess the strength of the hip flexor muscles.

chi-square analysis. To determine the degree of asso-ciation between LBP and physical characteristics,only those characteristics that we found to be signifi-cantly different between subjects with and withoutLBP were selected. Backward logistic regressionanalysis was used to determine the degree of associa-tion between each selected variable and LBP. Logisticregression analysis is a statistical procedure used toassess the degree of association between a dichoto-mous dependent variable and the independent vari-ables.68 This procedure can also be used to deter-mine the effect of independent variables on theprobability (likelihood) of occurrence of the depen-dent variable.68

3A

3B


RESULTS

Table 2 presents the ICC for each of the 15 mea-surements taken in the pilot study. Except for theindirect measurement of the length of the hip flexor(ICC = 0.72 and 0.75), abdominal (ICC = 0.79) andtriceps surae (ICC = 0.77 and 0.78) muscles, allother ICC values were greater than 0.80.

The result of the ANOVA revealed that sex byhealth status was significant for back extensor musclelength, back extensor muscle endurance, and ab-dominal muscle strength at 0.05 (Table 3).

TABLE 2. Intraclass correlation coefficient (ICC) values forintratester and intertester reliability for the 15 measurements per-formed in the study (n = 40 subjects).

ICC

Measurements Tester 1* Tester 2* Intertester

Lumbar lordosis 0.92 0.89 0.90Back extensor length 0.95 0.91 0.90Pelvic tilt 0.89 0.86 0.85Abdominal muscle length 0.85 0.84 0.79Iliopsoas length 0.82 0.72 0.75Hamstrings length 0.91 0.91 0.90Hip adductor length 0.94 0.93 0.87Triceps surae length 0.81 0.78 0.77Back extensor endurance 0.98Abdominal muscle strength 0.89Hip flexor strength 0.98Hip extensor strength 0.96Hip abductor strength 0.92Hip adductor strength 0.94Foot arch 0.94

* Model (3,1) Model (2,1)

Therefore, these factors were analyzed separately formen and women. We used pooled data to comparemeans of the other variables, which had no signifi-cant health status by sex interaction effect. The chi-square analysis showed a significant difference(P = 0.04) in the length of the iliotibial band and nosignificant difference in the leg length discrepancy(P = 0.47) between the symptomatic andasymptomatic subjects. Back extensor endurance, thelength of the hamstring muscles, iliotibial band tight-ness, back extensor muscle length, and the strengthof the hip flexor, hip extensor, hip adductor, hip ab-ductor and abdominal muscles were found to be sig-nificantly different between asymptomatic subjectsand those with LBP.

We used backward logistic regression analysis todetermine the association between LBP and the vari-ables, which showed a significant difference betweensubjects with and without LBP (back extensor endur-ance, hamstrings muscle length, iliotibial band tight-ness, back extensor muscle length, and hip flexor,hip extensor, hip adductor, hip abductor, and ab-dominal muscle strength). Both in pooled and sepa-rate data analysis for men and women, among all thefactors that remained in the model, endurance ofthe back extensor muscles had the highest associa-tion with LBP (Figure 4). Some of the variables wereeliminated from the model due to the fact that inlogistic regression analysis when one variable is re-tained in the model, any other variable highly corre-lated with it will be eliminated from the model. Inthis study, for example, since hip flexor and hip ad-ductor strengths were retained in the model, hip ex-tensor and hip abductor strengths, which were highlycorrelated with them (Table 4), were eliminated.

TABLE 3. Mean and standard deviation (SD) of the tested variables from 2 2 ANOVA table.

Variables Asymptomatic LBP P Value

Lumbar lordosis () 35 13 34 14 0.21Back extensor length, men ()* 23 7 18 8 0.01Back extensor length, women ()* 19 7 16 7 0.009Iliopsoas length () 5 2 5 2 0.58Hip adductor length () 47 9 47 10 0.99Hamstrings length () 149 9 144 10 0.01Abdominal muscle length 0.53 0.06 0.54 0.06 0.80Foot arch 0.68 0.15 0.65 0.14 0.08Triceps surae length () 13 4 13 4 0.69Back extensor endurance, men (s)* 79 45 29 24 0.01Back extensor endurance, women (s)* 57 36 22 15 0.01Hip flexor strength (kPa) 43 11 36 11 0.01Hip extensor strength (kPa) 29 7 22 7 0.01Hip abductor strength (kPa) 32 7 26 8 0.01Hip adductor strength (kPa) 31 7 23 8 0.01Pelvic tilt () 7 2 7 3 0.78Abdominal muscle strength, men (kPa)* 31 5 24 8 0.01Abdominal muscle strength, women (kPa)* 23 4 18 5 0.01

* These variables had a significant sex-by-health-status interaction at 0.05 level; therefore, they were analyzed separately for men and women.The other variables had no significant sex-by-health-status interaction; therefore, the comparison of means from the asymptomatic and the low backpain (LBP) group was conducted from the main effect of health status.


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FIGURE 4. Degree of association between low back pain (LBP) andvarious physical characteristics. (BEXTend, back extensor muscleendurance; ABDOst, abdominal muscle strength; BEXTlen, backextensor muscle length; HFst, hip flexor muscle strength; HADDst,hip adductor muscle strength; HAMlen, hamstrings muscle length.)Among all the factors that had a significant association with LBP,endurance of the back extensor muscles showed the highestassociation. Contrary to the pooled data, the length of the hamstringmuscles in men and women and the strength of the hip flexor andhip adductor muscles in women showed no significant associationwith LBP.

DISCUSSION

Endurance of Back Extensor Muscles

Our data indicate that among all the physical char-acteristics measured, the endurance of the back ex-

tensor muscles has the highest association with LBP.This finding is in accordance with other studiesshowing a significant decrease in back extensormuscle endurance in patients with chronicLBP.3,50,51,53,59,63,103 Biering-Sorensen8 identified poorback extensor muscle endurance as an important riskfactor for LBP. Others have suggested that a test ofback extensor endurance be used as a screening toolin the selection of workers for strenuous jobs.17

Trunk extensors are classified as posturalmuscles.61 Because these muscles are rich in largerdiameter type I muscle fibers,112 they are suited tosupport low levels of activity for long periods oftime.85 Electromyographic (EMG) studies, however,indicate that the paraspinal muscles in patients withLBP have a faster fatigue rate compared with thosein asymptomatic subjects.3,7,56,89,94,102 Investigatorshave attributed the decreased muscle endurancefound in patients with LBP to various factors, such ashigher muscle metabolite level resulting from pro-longed muscle tension and spasm,2 higher propor-tion of type II muscle fibers in paraspinal muscles,101

muscle deconditioning,102 impaired muscle coordina-tion and unequal distribution of back extensormuscle force,101 and inhibition and atrophy of theparaspinal muscles,102 especially the lumbarmultifidus muscles,24,80 in response to pain and de-

TABLE 4. Correlation matrix (r values) among tested factors. (Values in bold have a P value of 0.05.)

Variables

Lum-bar

Lordosis

BackExten-

sorLength

Iliop-soas

Length

HipAdduc-

torLength

Ham-stringsLength

Abdom-inal

LengthFootArch

Gastroc-soleusLength

HipFlexor

Strength

HipExten-

sorStrength

HipAbduc-

torStrength

HipAdduc-

torStrength

PelvicTilt

Abdom-inal

Strength

Back extensorlength

0.14

Iliopsoas length 0.05 0.01Hip adductor

length0.24 0.21 0.07

Hamstringslength

0.11 0.03 0.06 0.22

Abdominalmuscle length

0.36 0.21 0.001 0.35 0.20

Foot arch 0.002 0.05 0.09 0.008 0.05 0.04Gastrocsoleus

length0.08 0.19 0.02 0.26 0.13 0.15 0.03

Hip flexorstrength

0.17 0.18 0.08 0.28 0.04 0.370.03 0.19

Hip extensorstrength

0.11 0.15 0.09 0.34 0.11 0.310.03 0.17 0.82

Hip abductorstrength

0.16 0.13 0.10 0.35 0.13 0.300.001 0.20 0.89 0.81

Hip adductorstrength

0.13 0.18 0.06 0.36 0.09 0.320.03 0.20 0.88 0.82 0.89

Pelvic tilt 0.10 0.005 0.07 0.003 0.08 0.22 0.003 0.06 0.03 0.07 0.01 0.02Abdominal

musclestrength

0.07 0.09 0.17 0.24 0.08 0.23 0.008 0.25 0.67 0.69 0.63 0.66 0.09

Back extensorendurance

0.06 0.05 0.01 0.15 0.25 0.05 0.05 0.09 0.39 0.42 0.37 0.38 0.01 0.43

BEXTend ABDOst BEXTlen HFst HADDst HAMlen0

25

50

75

100

125PooledMalesFemales

Factors

-2L

ogLR


creased activity.63 Hides et al48 showed a 31% de-creased cross-sectional area in lumbar multifidusmuscles in patients with LBP, which did not resolveautomatically after remission of painful symptoms.47

According to Roy et al,101 these muscles consistentlydemonstrate a higher fatigue rate in patients withLBP. Wilder and Aleksiev122 showed that fatiguederector spinae muscles have a longer response timeand decreased ability to tolerate sudden loads. Exces-sive uncontrolled loads may induce strain on thefacet joints and the passive structure of the lumbarspine, resulting in LBP.20 The high association be-tween the endurance of back extensor muscles andLBP found in our study complements the results ofprevious studies which indicated that improvement oferector spinae endurance is an important factor inpreventing8 and treating86,95 LBP. Some investigatorshave recommended flexion exercises to decreaselumbar lordosis,66,76 and others have advocated ex-tension exercises to increase lumbar lordosis28,92,95 inthe treatment of LBP. The fact that flexion and ex-tension exercises have the same effect on reducingLBP16,30,33,41,78,127 indicates that improved symptomsmay be due to enhanced muscle endurance and co-ordination between the trunk flexor and extensormuscles50 rather than changes in the size of the lum-bar lordosis.

Length of Back Extensor Muscles

The results of this study show a significantly lowerflexibility of the back extensor muscles in subjectswith LBP. Similar findings have been reported byothers.14,52,70,117 Kendall65 believes that back extensormuscle tightness is due to abdominal muscle weak-ness and prolonged sitting posture. Norris91 statedthat back extensor muscle tightness in patients with

LBP is a compensatory mechanism in response totight hip flexor and weak gluteal and abdominalmuscles. Although our data shows a significant butweak association between back extensor musclelength and hip extensor muscle strength (r = 0.15, P= 0.008) (Table 4), we found that the length of thehip flexors (r = 0.01, P = 0.83) and the strength ofthe abdominal muscles (r = 0.09, P = 0.08) were notassociated with the length of the back extensormuscles. Our data showed a much stronger associa-tion between LBP and the endurance of the backextensor muscles than between LBP and the lengthof these muscles both in men and women (Table 5).It is suggested that back extensor muscle tightness inpatients with LBP may be due to adaptive shorteningof these muscles in response to muscle fatigue andoveruse.

Abdominal Muscle Strength

Similar to previous studies,3,44,73,83,88 our data indi-cate that patients with LBP have significantly lowerabdominal muscle strength compared withasymptomatic subjects. It is commonly hypothesizedthat weak abdominal muscles cause anterior pelvictilt and increased lumbar lordosis.18,61,65,123 Althougha significant association between the strength of theabdominal muscles and LBP was found (Table 5),the data in our study did not support the stated hy-pothesis. In the study, the strength of the abdominalmuscles was not correlated with the size of the lum-bar lordosis (r = 0.07) or pelvic tilt (r = 0.09). Otherinvestigators have also not associated the size of lum-bar lordosis or pelvic tilt with the strength of the ab-dominal muscles.121,124 Levine et al75 found that an8-week strengthening exercise program for the ab-dominal muscles increased muscle strength but had

TABLE 5. Degree of association between the tested variables and low back pain (LBP) from backward logistic regression analysis.

Pooled Data Men Women

Factors 2LogLR P Value 2LogLR P Value 2LogLR P Value

Back extensorendurance

110.63 0.001 54.30 0.001 62.93 0.001

Back extensorlength

10.56 0.002 6.83 0.008 7.11 0.007

Abdominal musclestrength

7.30 0.006 6.36 0.01 20.2 0.001

Hip flexor strength 18.59 0.001 4.91 0.02 N/S Hip adductors

strength10.16 0.001 3.90 0.04 N/S

Hamstrings length 6.64 0.01 N/S N/S

Among all the factors tested, the endurance of the back extensor muscles had the highest association with LBP. Originally, 9 factors were included inthe model. The factors that had no significant association with LBP or were highly correlated with 1 of the retained variables were eliminated throughbackward logistic regression analysis. N/S indicates nonsignificant factors that were eliminated from the model. 2LogLR is an index in logisticregression showing the degree of association between each factor and LBP. The higher the value of 2LogLR, the higher the likelihood of that factorbeing associated with LBP.


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no effect on the size of the lumbar lordosis of thesubjects. Moreover, the results of this study, in agree-ment with others,30,41,87,96 indicated that the size ofthe lumbar lordosis and pelvic tilt was not associatedwith LBP. More research is needed to describe thecause of abdominal muscle weakness in patients withLBP.

Hamstring Muscle Length

A logistic regression analysis, which accounted forsex effect, showed no significant association betweenthe length of the hamstring muscles and LBP (Table5). This finding is in accordance with Hellsing,45

who studied hamstrings tightness in 600 young menover a 4-year period and found no association be-tween hamstrings tightness and LBP or the incidenceof back pain during the follow-up period. This studyand several others, however, showed a significant dif-ference in hamstrings length between subjects withand without LBP.52,64,84 Because the hamstringmuscles attach to the ischial tuberosity, it is hypoth-esized that tightness of these muscles may induceposterior pelvic tilt, resulting in a flat back andLBP.18,65,105 Our data, however, showed no significantassociation between the length of the hamstringmuscles and pelvic tilt (r = 0.08) or the size of thelumbar lordosis (r = 0.11). Similar findings havebeen reported elsewhere.35,115 Moreover, the resultsof this study and others6,21,27,30,37,41,87,96,121,124 indi-cate that LBP is not associated with the size of thelumbar lordosis or pelvic tilt. Van Wingerden et al118

suggest that hamstrings tightness in patients withLBP is a compensatory mechanism secondary to pel-vic instability. Considering these findings, the statedhypothesis regarding the effect of hamstrings tight-ness on LBP requires re-evaluation.

Hip Flexor Muscles

By virtue of iliopsoas attachment to the pelvis andlumbar spine, some investigators have assumed thattightness of this muscle affects the size of the lumbarlordosis and causes LBP.18,65,97,105 Biomechanicalanalysis has revealed that the iliopsoas muscle, whichgenerates significant compressive forces, exerts verysmall rotatory movement on the vertebrae and hasno substantial action on the lumbar spine.9 Otherstudies investigating this assumption have found noassociation between iliopsoas muscle length and lum-bar lordosis60,116,124 or LBP.4 In agreement with theliterature, this study found no significant associationbetween the size of the lumbar lordosis (r = 0.05)or pelvic tilt (r = 0.07) and the length of the hipflexor muscles in subjects with LBP. Furthermore, nosignificant difference was found in the length of thehip flexor muscles between subjects with and withoutLBP, and no association was found between the

length of these muscles and LBP. Our data, however,showed a statistically significant association betweenthe strength of the hip flexor muscles and LBP inmen (Table 5). Hip flexors in subjects with LBP weresignificantly weaker than in those without LBP.Bachrach4 believes that laxity and mechanical insta-bility in the lumbosacral area due to iliopsoas muscleweakness can stimulate nociceptors in the surround-ing soft tissue, resulting in pain. The reason that ourdata did not show a significant relationship betweenLBP and hip flexor muscle strength in women maybe due to the data analysis used. Backward logisticregression analysis maintains the factors with thestrongest association with the dependent variable inthe model and eliminates the rest. When all the fac-tors were included in the model, the strength of thehip flexor muscles had a significant association withLBP in both women (2LogLR = 7.44, P = 0.006)and men (2LogLR = 7.15, P = 0.007). Separatedata analysis for men and women, however, showedthat in women, the strength of the abdominalmuscles and the endurance and length of the backextensor muscles accounted for greater variability ofdata than they did in men (Figure 4). Therefore, hipflexor strength was eliminated as a weak variable inwomen. In men, the stated factors accounted for lessvariability of data, allowing hip flexor strength to re-main in the model as a factor significantly correlatedwith LBP (Table 5).

CONCLUSION

It appears that muscle weakness is associated withLBP and that structural factors, such as the size ofthe lumbar lordosis, pelvic tilt, foot arch, leg lengthdifference, and the length of abdominal, iliopsoas,triceps surae, and hip adductor muscles, are not as-sociated with LBP. Our data show no difference inthese structural factors between subjects with andwithout LBP and showed no association betweenthese factors and LBP. We assume, as also stated byothers,50,72 that decreased back extensor muscle en-durance is an important factor in chronic LBP. Weagree with other investigators who have proposedincreased activity and endurance exercises to reducethe occurrence of LBP.47,93,98,104

ACKNOWLEDGMENT

The authors would like to thank Ms. Kathy Gan-non for assistance in preparing this manuscript.

REFERENCES1. Alston W, Carlson KE, Feldman DJ, Grimm Z,

Gerontinos E. A quantitative study of muscle factors inthe chronic low back syndrome. J Am Geriatr Soc.1966;14:10411047.


2. Armstrong RB. Mechanism of exercise-induced delayedonset muscular soreness: A brief review. Med SciSports Exerc. 1984;16:529538.

3. Ashmen KJ, Swanik CB, Lephart SM. Strength andflexibility characteristics of athletes with chronic lowback pain. J Sport Rehabil. 1996;5:275286.

4. Bachrach RM. Psoas dysfunction/insufficiency, sacro-iliac dysfunction and low back pain. In: Vleeming A,Mooney V, Dorman T, Snijders C, Stoeckart R, eds.Movement Stability and Low Back Pain. The EssentialRole of the Pelvis. New York, NY: ChurchillLivingstone; 1997;309318.

5. Battie MC, Bigos SJ, Fisher LD, Hansson TH, JonesME, Wortley MD. Isometric lifting strength as a predic-tor of industrial back pain reports. Spine. 1989;14:851856.

6. Beninato M, Hudson KR, Price KS. A study of thecorrelation among lumbar lordosis, pelvic tilt, ham-string and hip flexor muscle length. J Orthop SportsPhys Ther. 1993;17:61.

7. Biedermann HJ, Shanks GL, Inglis J. Median frequencyestimates of paraspinal muscles: Reliability analysis.Electromyogr Clin Neurophysiol. 1990;30:8388.

8. Biering-Sorensen F. Physical measurements as risk indi-cators for low back trouble over a one-year period.Spine. 1984;9:106119.

9. Bogduk N, Pearcy M, Hadfield G. Anatomy andbiomechanics of psoas major. Clin Biomech.1992;7:109119.

10. Bohannon RW. Cinematographic analysis of the pas-sive straight-leg-raising test for hamstring musclelength. Phys Ther. 1982;62:12691274.

11. Botte RR. An interpretation of the pronation syndromeand foot types of patients with low back pain. J AmPodiatry Assoc. 1981;71:243253.

12. Builder MA, Marr SJ. Case history of a patient with lowback pain and cavus feet. J Am Podiatry Assoc.1980;70:299301.

13. Burdett RG, Brown KE, Fall MP. Reliability and validityof four instruments for measuring lumbar spine andpelvic positions. Phys Ther. 1986;66:677684.

14. Burton AK. Regional lumbar sagittal mobility; measure-ment by flexicurves. Clin Biomech. 1986;1:2026.

15. Burton AK, Tillotson KM. Is recurrent low back troubleassociated with increased lumbar sagittal mobility? JBiomed Eng. 1989;11:245248.

16. Buswell J. Low back pain: a comparison of twotreatment programmes. NZJ Physiother. 1982;10:1317.

17. Cady LD, Bischoff DP, OConnell ER, Thomas PC,Allan JH. Strength and fitness and subsequent backinjuries in firefighters. J Occup Med. 1979;21:269272.

18. Calliet R. Low Back Pain Syndrome. 3rd ed. Philadel-phia, PA: FA Davis; 1981.

19. Carr D, Gilbertson L, Frymoyer J, Krag M, Pope M.Lumbar paraspinal compartment syndrome. A casereport with physiologic and anatomic studies. Spine.1985;10:816820.

20. Chok B, Lee R, Latimer J, Tan SB. Endurance trainingof the trunk extensor muscles in people with subacutelow back pain. Phys Ther. 1999;79:10321042.

21. Christie HJ, Kumar S, Warren SA. Postural Aberrationsin Low Back Pain. Arch Phys Med Rehabil.1995;76:218224.

22. Chu WC, Lee SH, Chu W, Wang TJ, Lee MC. The useof arch index to characterize arch height: A digitalimage processing approach. IEEE Trans Biomed Eng.1995;42:10881093.

23. Cibulka MT. Low back pain and its relation to thehip and foot. J Orthop Sports Phys Ther. 1999;29:595601.

24. Cooper RG, St Clair Forbes W, Jayson MI. Radio-graphic demonstration of paraspinal muscle wasting inpatients with chronic low back pain. Br J Rheumatol.1992;31:389394.

25. Cummings G, Scholz JP, Barnes K. The effect ofimposed leg length difference on pelvic bone symme-try. Spine. 1993;18:368373.

26. Cyriax FE. Antero-posterior tilt of the pelvis. Brit JChilds Dis. 1924;21:279283.

27. Day JW, Smidt GL, Lehmann T. Effect of pelvic tilt onstanding posture. Phys Ther. 1984;64:510516.

28. Delitto A, Cibulka MT, Erhard RE, Bowling RW,Tenhula JA. Evidence for use of an extension-mobilization category in acute low back syndrome: Aprescriptive validation pilot study. Phys Ther.1993;73:216222; discussion 223228.

29. Dettori JR, Bullock SH, Sutlive TG, Franklin RJ, Pa-tience T. The effects of spinal flexion and extensionexercises and their associated postures in patients withacute low back pain. Spine. 1995;20:23032312.

30. During J, Goudfrooij H, Keessen W, Beeker TW, CroweA. Toward standards for posture. Postural characteris-tics of the lower back system in normal and pathologicconditions. Spine. 1985;10:8387.

31. Eifert-Mangine MA, Bilbo JT. Conservative managementof patellofemoral conditions. In: Mangine RE, ed.Physical Therapy of the Knee. 2nd ed. New York, NY:Churchill Livingstone; 1995.

32. Elnaggar IM, Nordin M, Sheikhzadeh A, ParnianpourM, Kahanovitz N. Effects of spinal flexion and exten-sion exercises on low-back pain and spinal mobility inchronic mechanical low-back pain patients. Spine.1991;16:967972.

33. Friberg O. Clinical symptoms and biomechanics oflumbar spine and hip joint in leg length inequality.Spine. 1983;8:643651.

34. Gajdosik RL, Guiliani CA, Bohannon RW. Passivecompliance and length of the hamstring muscle ofhealthy men and women. Clin Biomech 1990;5:2329.

35. Gajdosik RL, Hatcher CK, Whitsell S. Influence of shorthamstring muscles on the pelvis and lumbar spine instanding and during the toe-touch test. Clin Biomech.1992;7:3842.

36. Gajdosik R, Lusin G. Hamstring muscle tightness:Reliability of an active-knee-extension test. Phys Ther.1983;63:10851088.

37. Gautier J, Morillon P, Marcelli C. Does spinal morphol-ogy influence the occurrence of low back pain? RevRhum Engl Ed. 1999;66:2934.

38. Giles LG, Taylor JR. Low-back pain associated with leglength inequality. Spine. 1981;6:510521.

39. Grundy PF, Roberts CJ. Does unequal leg length causeback pain? A case-control study. Lancet. 1984;2:256258.

40. Hansen FR, Bendix T, Skov P, et al. Intensive, dynamicback-muscle exercises, conventional physiotherapy, orplacebo-control treatment of low-back pain. A random-ized, observer-blind trial. Spine. 1993;18:98108.

41. Hansson T, Bigos S, Beecher P, Wortley M. The lumbarlordosis in acute and chronic low-back pain. Spine.1985;10:154155.

42. Helewa A, Goldsmith CH, Smythe HA. The modifiedsphygmomanometer-an instrument to measure musclestrength: a validation study. J Chronic Dis.1981;34:353361.

43. Helewa A, Goldsmith CH, Smythe HA. Patient, ob-server and instrument variation in the measurement of


RE

SE

AR

CH

RE

PO

RT

strength of shoulder abductor muscles in patients withrheumatoid arthritis using a modified sphygmomanom-eter. J Rheumatol. 1986;13:10441049.

44. Helewa A, Goldsmith C, Smythe H, Gibson E. Anevaluation of four different measures of abdominalmuscle strength: Patient, order and instrument varia-tion. J Rheumatol. 1990;17:965969.

45. Hellsing AL. Tightness of hamstring and psoas majormuscles. A prospective study of back pain in youngmen during their military service. Ups J Med Sci.1988;93:267276.

46. Hemborg B, Moritz U. Intra-abdominal pressure andtrunk muscle activity during lifting. II. Chronic low-back patients. Scand J Rehabil Med. 1985;17:513.

47. Hides JA, Richardson CA, Jull GA. Multifidus musclerecovery is not automatic after resolution of acute,first-episode low back pain. Spine. 1996;21:27632769.

48. Hides JA, Stokes MJ, Saide M, Jull GA, Cooper DH.Evidence of lumbar multifidus wasting ipsilateral tosymptoms in subjects with acute/subacute low backpain. Spine. 1994;19:165177.

49. Hoikka V, Ylikoski M, Tallroth K. Leg-length inequalityhas poor correlation with lumbar scoliosis. A radiologi-cal study of 100 patients with chronic low-back pain.Arch Orthop Trauma Surg. 1989;108:173175.

50. Holmstrom E, Moritz U, Andersson M. Trunk musclestrength and back muscle endurance in constructionworkers with and without low back disorders. Scand JRehabil Med. 1992;24:310.

51. Hultman G, Nordin M, Saraste H, Ohlsen H. Bodycomposition, endurance, strength, cross-sectional area,and density of mm erector spinae in men with andwithout low back pain. J Spinal Disord. 1993;6:114123.

52. Hultman G, Saraste H, Ohlsen H. Anthropometry,spinal canal width, and flexibility of the spine andhamstring muscles in 4555-year-old men with andwithout low back pain. J Spinal Disord. 1992;5:245253.

53. Ito T, Shirado O, Suzuki H, Takahashi M, Kaneda K,Strax TE. Lumbar trunk muscle endurance testing: Aninexpensive alternative to a machine for evaluation.Arch Phys Med Rehabil. 1996;77:7579.

54. Janda V. Muscles, central nervous motor regulation andback problems. In: Korr IM, ed. The NeurobiologicMechanisms in Manipulative Therapy. New York, NY:Plenum Press; 1978:2741.

55. Jasty M, Webster W, Harris W. Management of limblength inequality during total hip replacement. ClinOrthop. 1996;165171.

56. Jayasinghe WJ, Harding RH, Anderson JA, SweetmanBJ. An electromyographic investigation of posturalfatigue in low back paina preliminary study.Electromyogr Clin Neurophysiol. 1978;18:191198.

57. Jonson SR, Gross MT. Intraexaminer reliability,interexaminer reliability, and mean values for ninelower extremity skeletal measures in healthy navalmidshipmen. J Orthop Sports Phys Ther. 1997;25:253263.

58. Jorgensen K. Human trunk extensor muscles physiologyand ergonomics. Acta Physiol Scand Suppl.1997;637:158.

59. Jorgensen K, Nicolaisen T. Trunk extensor endurance:determination and relation to low-back trouble. Ergo-nomics. 1987;30:259267.

60. Jorgensson A. The iliopsoas muscle and lumbar spine.Aust J Physiother. 1993;39:125132.

61. Jull GA, Janda V. Muscles and motor control in lowback pain. In: Twomey LT, Taylor JR, eds. PhysicalTherapy of the Low Back. New York, NY: ChurchillLivingstone; 1987.

62. Junk S, Terjesen T, Rossvoll I, Braten M. Leg lengthinequality measured by ultrasound and clinical meth-ods. Eur J Radiol. 1992;14:185188.

63. Kankaanpaa M, Taimela S, Laaksonen D, Hanninen O,Airaksinen O. Back and hip extensor fatigability inchronic low back pain patients and controls. Arch PhysMed Rehabil. 1998;79:412417.

64. Kapandji IA. The Physiology of the Joints. 2nd ed.Edinburgh, UK: Churchill Livingstone; 1982.

65. Kendall FP, McCreary EK, Provance PG. Muscle Testingand Function. 4th ed. Philadelphia, PA: Lippincott,Williams and Wilkins, 1993.

66. Kendall PH, Jenkins HM. Exercise for backache: adouble blind control trial. Physiotherapy. 1968;54:154157.

67. Kisner C, Colby LA. Therapeutic Exercise: Foundationsand Techniques. 2nd ed. Philadelphia, PA: FA Davis;1990.

68. Kleinbaum DG, Kupper LL, Muller KE. Applied Regres-sion Analysis and Other Multivariable Methods. 2nded. North Scituate, MA: Duxbury Press; 1978.

69. Lampe HI, Swierstra BA, Diepstraten AF. Measurementof limb length inequality. Comparison of clinical meth-ods with orthoradiography in 190 children. ActaOrthop Scand. 1996;67:242244.

70. Lankhorst GJ, Van de Stadt RJ, Van der Korst JK. Thenatural history of idiopathic low back pain. A three-year follow-up study of spinal motion, pain andfunctional capacity. Scand J Rehabil Med.1985;17:14.

71. Lee D. The Pelvic Girdle: An Approach to Examinationand Treatment of the Lumbo-Pelvic-Hip Region. 2nded. New York, NY: Churchill Livingstone; 1999.

72. Lee JH, Hoshino Y, Nakamura K, Kariya Y, Saita K, ItoK. Trunk muscle weakness as a risk factor for low backpain. A 5-year prospective study. Spine. 1999;24:5457.

73. Lee JH, Ooi Y, Nakamura K. Measurement of musclestrength of the trunk and the lower extremities insubjects with history of low back pain. Spine.1995;20:19941996.

74. Leino P, Aro S, Hasan J. Trunk muscle function andlow back disorders: a ten-year follow-up study. JChronic Dis. 1987;40:289296.

75. Levine D, Walker R, Tillman LJ. The effect of abdomi-nal muscle strengthening on pelvic tilt and lumbarlordosis. Physiother Theory Pract. 1997;13:217226.

76. Lidstrom A, Zachrisson M. Physical therapy on lowback pain and sciatica. An attempt at evaluation.Scand J Rehabil Med. 1970;2:3742.

77. Magee DJ. Orthopedic Physical Assessment. 3rd ed.Philadelphia, PA: WB Saunders; 1997.

78. Manniche C, Hesselsoe G, Bentzen L, Christensen I,Lundberg E. Clinical trial of intensive muscle trainingfor chronic low back pain. Lancet. 1988;2:14731476.

79. Marras WS, Rangarajulu SL, Lavender SA. Trunk load-ing and expectation. Ergonomics. 1987;30:551562.

80. Mayer TG, Smith SS, Keeley J, Mooney V. Quantifica-tion of lumbar function. Part 2: sagittal plane trunkstrength in chronic low-back pain patients. Spine.1985;10:765772.

81. McCaw ST. Leg length inequality. Implications forrunning injury prevention. Sports Med. 1992;14:422429.


82. Mckenzie RA. The Lumbar Spine: Mechanical Diagno-sis and Therapy. Lower Hutt, New Zealand: SpinalPublications; 1981.

83. McNeill T, Warwick D, Andersson G, Schultz A. Trunkstrengths in attempted flexion, extension, and lateralbending in healthy subjects and patients with low-backdisorders. Spine. 1980;5:529538.

84. Mellin G. Correlations of hip mobility with degree ofback pain and lumbar spinal mobility in chroniclow-back pain patients. Spine. 1988;13:668670.

85. Moffroid MT. Endurance of trunk muscles in personswith chronic low back pain: assessment, performance,training. J Rehabil Res Dev. 1997;34:440447.

86. Moffroid MT, Haugh LD, Haig AJ, Henry SM, PopeMH. Endurance training of trunk extensor muscles.Phys Ther. 1993;73:107.

87. Mossavi SJ. The Effect of Lifestyle and Work-RelatedPhysical Activity on the Size of Lumbar Lordosis andChronic Low Back Pain in a Middle East Population.Tehran, Iran: University of Social Welfare and Rehabili-tation Sciences; 1998.

88. Nachemson A, Lindh M. Measurement of abdominaland back muscle strength with and without low backpain. Scand J Rehabil Med. 1969;1:6063.

89. Nicolaisen T, Jorgensen K. Trunk strength, back muscleendurance and low-back trouble. Scand J Rehabil Med.1985;17:121127.

90. Norkin CC, Levangie PK. Joint Structure and Function:A Comprehensive Analysis. 2nd ed. Philadelphia, PA:FA Davis Co.; 1992.

91. Norris CM. Spinal stabilization and muscle imbalanceand the low back. Physiotherapy. 1995;81:127138.

92. Nwuga G, Nwuga V. Relative therapeutic efficacy ofthe Williams and McKenzie protocols in back painmanagement. Physiother Pract. 1985;1:99105.

93. Panjabi MM. The stabilizing system of the spine. Part I.Function, dysfunction, adaptation, and enhancement. JSpinal Disord. 1992;5:383389; discussion 397.

94. Plowman SA. Physical activity, physical fitness, andlow back pain. Exerc Sport Sci Rev. 1992;20:221242.

95. Ponte JD, Jensen GJ, Kent BE. A preliminary report onthe use of the McKensie protocol versus Williamsprotocol in the treatment of low back pain. J OrthopSports Phys Ther. 1984;6:130139.

96. Pope MH, Bevins T, Wilder DG, Frymoyer JW. Therelationship between anthropometric, postural, muscu-lar, and mobility characteristics of males ages 1855.Spine. 1985;10:644648.

97. Porterfield JA, De Rosa C. Mechanical Low Back Pain:Perspectives in Functional Anatomy. 2nd ed. Philadel-phia, PA: WB Saunders; 1998.

98. Robison R. The new back school prescription: stabili-zation training. Part I. Occup Med. 1992;7:1731.

99. Roncarati A, McMullen W. Correlates of low back painin a general population sample: A multidisciplinaryperspective. J Manipulative Physiol Ther. 1988;11:158164.

100. Rothbart BA, Estabrook L. Excessive pronation: A majorbiomechanical determinant in the development ofchondromalacia and pelvic lists. J Manipulative PhysiolTher. 1988;11:373379.

101. Roy SH, De Luca CJ, Casavant DA. Lumbar musclefatigue and chronic lower back pain. Spine.1989;14:9921001.

102. Roy SH, Oddsson LIE. Classification of paraspinalmuscle impairments by surface electromyography. PhysTher. 1998;78:838851.

103. Salminen JJ, Oksanen A, Maki P, Pentti J, Kujala UM.Leisure time physical activity in the young. Correlation

with low-back pain, spinal mobility and trunk musclestrength in 15-year-old school children. Int J SportsMed. 1993;14:406410.

104. Sanders G, Stavrakas P. A technique for measuringpelvic tilt. Phys Ther. 1981;61:4950.

105. Schafer RC. Clinical Biomechanics, MusculoskeletalActions and Reactions. 2nd ed. Baltimore, MD: Will-iams and Wilkins; 1987.

106. Shirado O, Ito T, Kaneda K, Strax TE. Concentric andeccentric strength of trunk muscles: influence of testpostures on strength and characteristics of patients withchronic low-back pain. Arch Phys Med Rehabil.1995;76:604611.

107. Soukka A, Alaranta H, Tallroth K, Heliovaara M.Leg-length inequality in people of working age. Theassociation between mild inequality and low-back painis questionable. Spine. 1991;16:429431.

108. SPSS Base 10.0: Application Guide. Chicago, IL: SPSSInc.; 1999.

109. Staheli LT, Chew DE, Corbett M. The longitudinal arch.A survey of eight hundred and eighty-two feet innormal children and adults. J Bone Joint Surg Am.1987;69:426428.

110. Svensson HO, Andersson GBJ, Johansson S, Wilhelms-son C, Vedin A. A retrospective study of low back painin 38- to 64-year-old women. Frequency and occur-rence and impact on medical services. Spine.1988;13:548552.

111. ten Brinke A, van der Aa HE, van der Palen J,Oosterveld F. Is leg length discrepancy associated withthe side of radiating pain in patients with a lumbarherniated disc? Spine. 1999;24:684686.

112. Thorstensen A, Carlson H. Fiber types in humanlumbar back muscles. Acta Physiol Scand.1987;131:195202.

113. Thorstensson A, Arvidson A. Trunk muscle strength andlow back pain. Scand J Rehabil Med. 1982;14:6975.

114. Tillotson KM, Burton AK. Noninvasive measurement oflumbar sagittal mobility. An assessment of theflexicurve technique. Spine. 1991;16:2933.

115. Toppenberg R, Bullock M. Normal lumbo-pelvicmuscle lengths and their interrelationships in adoles-cent females. Aust J Physiother. 1990;36:105109.

116. Toppenberg RM, Bullock MI. The interrelation of spinalcurves, pelvic tilt and muscle lengths in the adolescentfemale. Aust J Physiother. 1986;32:612.

117. Troup JD, Foreman TK, Baxter CE, Brown D. 1987Volvo award in clinical sciences. The perception ofback pain and the role of psychophysical tests of liftingcapacity. Spine. 1987;12:645657.

118. van Wingerden JP, Vleeming A, Kleinrensink GJ,Stoeckart R. The role of the hamstring in pelvic andspinal function. In: Vleeming A, Mooney V, Dorman T,Snijders C, Stoeckart R, eds. Movement Stability andLow Back Pain. The Essential Role of the Pelvis. NewYork, NY: Churchill Livingstone; 1997:207210.

119. Waddell G. 1987 Volvo award in clinical sciences. Anew clinical model for the treatment of low-back pain.Spine. 1987;12:632644.

120. Waddell G, Somerville D, Henderson I, Newton M.Objective clinical evaluation of physical impairment inchronic low back pain. Spine. 1992;17:617628.

121. Walker ML, Rothstein JM, Finucane SD, Lamb RL.Relationships between lumbar lordosis, pelvic tilt, andabdominal muscle performance. Phys Ther.1987;67:512516.

122. Wilder DG, Aleksiev AR, Magnusson ML, Pope MH,Spratt KF, Goel VK. Muscular response to sudden load.A tool to evaluate fatigue and rehabilitation. Spine.1996;21:26282639.


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RE

PO

RT

123. Williams PC. Examination and conservative treatmentfor disc lesions of the lower spine. Clin Orthop.1955;5:2840.

124. Youdas JW, Garrett TR, Harmsen S, Suman VJ, CareyJR. Lumbar lordosis and pelvic inclination ofasymptomatic adults. Phys Ther. 1996;76:10661081.

125. Youdas JW, Suman VJ, Garrett TR. Reliability of mea-surements of lumbar spine sagittal mobility obtained

with the flexible curve. J Orthop Sports Phys Ther.1995;21:1320.

126. Yrjonen T, Hoikka V, Poussa M, Osterman K. Leg-length inequality and low-back pain after Perthesdisease: A 2847-year follow-up of 96 patients. J SpinalDisord. 1992;5:443447.

127. Zylbergold RS, Piper MC. Lumbar disc disease: com-parative analysis of physical therapy treatments. ArchPhys Med Rehabil. 1981;62:176179.


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Relationship Between Mechanical Factors

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