Effect of abduction and external rotation of the hip joint on muscle onset time during prone hip extension with knee flexion

[Purpose] This study investigated the effect of hip position on muscle onset time during prone hip extension with knee flexion. [Subjects] The study included 21 healthy male volunteers. [Methods] Muscle onset times of the right gluteus maximus, right hamstrings, bilateral lumbar erector spinae, and bilateral lumbar multifidus were measured using surface electromyography during right hip extension with knee flexion in the prone position. Measurements were made with the hip in 3 positions: (1) neutral, (2) abduction, and (3) abduction and external rotation. [Results] Gluteus maximus onset relative to the hamstrings was significantly earlier with hip abduction and with hip abduction and external rotation compared with that with the hip in the neutral position. Gluteus maximus onset relative to the hamstrings was significantly earlier with hip abduction and external rotation compared with that with hip abduction. The bilateral multifidus and left lumbar erector spinae onset times relative to the hamstrings were significantly earlier with hip abduction and external rotation compared with those with hip abduction and with the hip in the neutral position. [Conclusion] Abduction and external rotation of the hip during prone hip extension with knee flexion is effective for advancing the onset times of the gluteus maximus, bilateral multifidus, and contralateral lumbar erector spinae.Key words: Prone hip extension with knee flexion, Hip joint position, Muscle onset time     

Effects of abdominal drawing-in during prone hip extension on the muscle activities of the hamstring,gluteus maximus,and lumbar erector spinae in subjects with lumbar hyperlordosis

[Purpose] The purpose of this study was to compare the effects of an abdominal drawing-in maneuver (ADIM), measured using a pressure bio-feedback unit, on the activities of the hamstring, gluteus maximus, and erector spinae muscles during prone hip extension. [Subjects and Methods] Thirty healthy adult subjects (14 male, 16 female), were recruited. Subjects’ lumbar lordosis and pelvic tilt angles were measured, and based on the results, the subjects were divided into two groups: a hyperlordotic lumbar angle (HLLA) group (n=15) and a normal lordotic lumbar angle (NLLA) group (n=15). The muscle activities of the hamstring and gluteus maximus, and of the erector spinae on the right side of the body, were recorded using surface electromyography. [Results] When performing ADIM with prone hip extension, the muscle activity of the gluteus maximus of the HLLA group significantly improved compared with that the NLLA group. [Conclusion] This study demonstrated that ADIM with prone hip extension was more effective at eliciting gluteus maximus activity in the HLLA group than in the NLLA group. Therefore, ADIM with prone hip extension may be useful for increasing the gluteus maximus activity of individuals with lumbar hyperlordosis.Key words: Abdominal drawing-in maneuver, Hyperlordotic lumbar angle, Prone hip extension     

Lumbar posture biomechanics and its influence on the functional anatomy of the erector spinae and multifidus

Abstract

Background:

Lumbar posture has a significant impact on the functional biomechanics of the erector spinae and multifidus muscles, which has implications for the loads placed on the tissues of the lumbar spine.

Objectives:

The objective of this review is to discuss the effects of lumbar posture on the functional biomechanics of the different divisions of the erector spinae and the multifidus muscle and its importance when developing clinical interventions.

Methods:

This review used the search engines PubMed, EBSCO, CINAHL and SCOPUS to identify studies investigating erector spinae and multifidus muscle architecture and the influence of lumbar posture on the biomechanical properties of these muscles and the resulting impact on spinal loading.

Results:

Changes in lumbar curvature alter muscle fascicle obliquity, lever arm distances, the length–tension relationships and muscle volume of the different divisions of erector spinae and multifidus, which impact on the spine's ability to resist moments and shear forces.

Conclusion:

Changes in lumbar posture influence the functional biomechanics of the different divisions of erector spinae and the multifidus muscles. Therapists should develop low back interventions that avoid end range of lumbar postures and optimise the functional biomechanics of the erector spinae and multifidus muscles and minimise loading on the lumbar spine.     

Comparison of the isolated contraction ratios of the hip extensors and erector spinae muscles of the lumbar region and thoracic muscles during different back extension exercises

[Purpose] This study compared the isolated contraction ratios of the hip extensors, erector spinae muscles of the lumbar region, and thoracic muscles during different back extension exercises. [Subjects] Twelve males participated in this study. [Methods] The subjects performed various back extension exercises. The activities of the T7 erector spinae muscles, L3 erector spinae muscles, and the gluteus maximus were measured, and the isolation contraction ratios were calculated. [Results] The isolated contraction ratio of the T7 erector spinae muscles significantly increased during exercise 2. The isolated contraction ratio of the gluteus maximus increased by a significant degree during exercise 1 compared with the other exercises. [Conclusion] This study demonstrated that the back extension exercises 1 and 2 can be applied to selectively exercise the hip extensors, thoracic muscles, and muscles of the lumbar region.Key words: Back extensor, Isolated contraction ratio, Selected exercise     

Selective Activation of Lumbar Paraspinal Muscles during Various Exercises in the Prone Position as Measured by EMG

[Purpose] This study compared the effects of three exercises performed in a prone position on the selective activation of the lumbar erector spinae (LES) and lumbar multifidus (LM) muscles in healthy males to investigate the effective method for selective activation of the LM. [Subjects] Twenty-two healthy males were recruited. Surface EMG data were collected from the right LES and LM muscles during three exercises: 1) trunk extension, 2) hip extension, and 3) the arm lift. [Results] The ratio of LM to LES EMG activity during hip extension was higher than those during trunk extension and the arm lift. [Conclusion] Hip extension in a prone position may be effective for selective activation of the lumbar multifidus muscles in healthy males.Key words: Lumbar erector spinae, Lumbar multifidus, Selective activation     

Effect of postural angle on back muscle activities in aging female workers performing computer tasks

[Purpose] This study investigated the effects of postural angle on back muscle activity during a computer task in aging women. [Subjects] Seventeen women ≥50 years old participated. [Methods] The participants were instructed to perform computer-related tasks for 20 minutes on a workstation that simulated typical office working conditions. Back posture was measured from the measured trunk and pelvic angles. Electromyography activities were recorded simultaneously from the cervical erector spinae, longissimus, and multifidus muscles. [Results] The lowest mean percentages of maximum voluntary contraction for the cervical erector spinae and longissimus muscles were obtained when the upper trunk and pelvic angles were between 0° to −5° from the sagittal plane. The back muscle activities increased as the upper trunk and pelvic angles exceeded 0°. Statistical analysis showed significant correlations between upper trunk angle and cervical erector spinae and longissimus muscle activities. Similarly, pelvic angle was significantly correlated with cervical erector spinae and multifidus muscle activities. [Conclusion] A neutral back posture minimizes muscle activities in aging women performing computer tasks.Key words: Postural angle, Muscle activity, Aging     

Electromyography activity of selected trunk muscles during cardiopulmonary resuscitation

Background

Understanding trunk muscle activity during chest compression may improve cardiopulmonary resuscitation (CPR) training strategies of CPR or prevent low back pain. This study investigates the trunk muscle activity pattern of chest compression in health care providers to determine the pattern alternation during chest compression.

Methods

Thirty-one experienced health care providers performed CPR for 5 minutes at a frequency of 100 compressions per minute. An electromyography (EMG) system was used to record muscle activity in the first minute, the third minute, and the fifth minute. Electrodes were placed bilaterally over the pectoralis major, latissimus dorsi, rectus abdominis, erector spinae, and gluteus maximus. We calculated the root mean square (RMS) value and maximal amplitude of the EMG activity, median frequency, and delivered force.

Results

The maximal amplitude of EMG of the pectoralis major, erector spinae, and rectus abdominis showed large muscle activity above 45% of maximal voluntary contraction under chest compression. There were no significant differences in the RMS value of one chest compression cycle (RMS_100%) and median frequency for all muscles at the first, third, and fifth minutes. Only gluteus maximus showed significant imbalance. The EMG ratios (erector spinae/rectus abdominis; erector spinae/gluteus maximus) increased significantly over time. The delivered force, compression depth, and number of correct depth decreased significantly over time.

Conclusion

We suggest that the muscle power training for the pectoralis major, erector spinae, and rectus abdominis could be helpful for health care providers. Keeping muscle activity balance of bilateral gluteus maximus and maintaining the same level of EMG ratios might be the keys to prevent low back pain while performing CPR.     

Intraclass correlation coefficient of trunk muscle thicknesses in different positions measured using ultrasonography

[Purpose] This study aimed to clarify the required number of measurements to calculate trunk muscle thickness at each position. [Participants and Methods] The participants were 30 elderly males aged >65 years. The right lumbar multifidus (L2), lumbar multifidus (L5), erector spinae, transversus abdominis, internal oblique, and external oblique muscle thicknesses were measured on longitudinal images obtained using ultrasonography in the lying, sitting, and standing positions. Two measurement values for each muscle thickness was used to calculate the intraclass correlation coefficient (1.1–1.5). [Results] The intraclass correlation coefficients of the abdominal muscle thickness measurements with “great reliabilities” were as follows: 1.3–1.5 for the external oblique muscle and 1.2–1.5 for the internal oblique and transversus abdominis muscles in the lying position; 1.3–1.5 for the external oblique and transversus abdominis muscles and 1.2–1.5 for the internal oblique muscle in the sitting position; the intraclass correlation coefficient in the standing position was 1.5 for the external oblique muscle 1.1–1.5 for the internal oblique muscle and 1.3–1.5 for the transversus abdominis muscle. In all the positions, the intraclass correlation coefficient of the measurements of the back-muscle thicknesses ranged from 1.1 to 1.5 for the right lumbar multifidus (L2), lumbar multifidus (L5), and erector spinae. [Conclusion] Depending on the posture, the abdominal muscles require multiple measurements, whereas the back muscles only require a single measurement.Key words: Intraclass correlation coefficient, Trunk muscle thicknesses, Ultrasonography     

Sonoelastography of the trunk and lower extremity muscles in a case of Duchenne muscular dystrophy

Duchenne muscular dystrophy (DMD) is a rare genetic disorder typically presenting with muscle weakness and reduced tone of trunk and lower extremities. The sonoelastographic properties of DMD are poorly understood. We describe sonoelastographic characteristics of a patient’s trunk and lower extremity musculature. An 8-year-old male presented with a 5-year history of DMD. Sonoelastographic measures of the gluteus maximus and medius, lumbar erector spinae, rectus abdominis, rectus femoris, biceps femoris, tibialis anterior, medial and lateral gastrocnemius muscles were obtained. Sonoelastography demonstrated increased elasticity by elevated kiloPascals (kPa) across all muscles, except the lumbar erector spinae. Patient values were compared to an age-matched healthy control. These abnormal sonoelastographic findings reflected the pathological mechanical properties of DMD. Sonoelastography was valuable for characterizing the mechanical properties of normal and abnormal muscle tissue. There is limited information on the sonoelastography application to DMD. Sonoelastography may serve as a useful measure for diagnosis and monitoring clinical outcomes for DMD.     

Effects of slouching and muscle contraction on the strain of the iliolumbar ligament

The study consisted of biomechanical modelling and in vitro experiments. The objective of the study was to find a mechanical cause of acute low back pain (LBP) in everyday situations. The precise mechanism producing LBP is still under discussion. Most biomechanical studies link the concepts of stooped postures and buckling instability of the spine under high compressive load. No biomechanical model addresses situations with small or neglectable compressive spinal load. The proposed conceptual model describes strain on the iliolumbar ligaments (ILs) when slouching from standing upright. Delayed or absent recruitment of back muscles that protect against hyperkyphosis of the lumbar spine is a conditional factor. Erector spinae and multifidus muscle forces are included, representing a bifurcation in back muscle force: one part acting on the iliac bones and one part acting on the sacrum. The multifidus muscle action on the sacrum may produce nutation which can be counteracted by pelvic floor muscles, which would link back problems and pelvic floor problems. The effect of simulated muscle tension on the ILs and the L5-S1 intervertebral disc angle was measured using embalmed specimens. Forces were applied to simulate erector spinae and sacral part of multifidus tension, bilateral up to 100 N each. Strain gauge sensors registered elongation of the ILs. Explorative biomechanical model calculations show that dynamic slouching, driven by upper body weight and (as an example) rectus abdominis muscle force may produce failure load of the spinal column and the ILs. The quasi-static test on embalmed specimens showed a significant increase of IL elongation with simulated rectus abdominis muscle force. Adding erector spinae or multifidus muscle tension eased the ILs. Sudden slouching of the upright trunk may create failure risk for the spine and ILs. This loading mode may be prevented by controlling loss of lumbar lordosis with erector spinae and multifidus muscle force.     

Application of Ultrasonography in the Assessment of Abdominal and Lumbar Trunk Muscle Activity in Participants With and Without Low Back Pain: A Systematic Review

ObjectiveThe purpose of this study was to systematically review the literature regarding which condition (task, position, or contraction type), changes in muscle thickness could be interpreted as muscle activity of trunk muscles.MethodsStudies that assessed the correlation between changes in muscle thickness measured with ultrasonography (US) and electromyography (EMG) activity were included. Only the data related to abdominal and lumbar trunk muscles in participants with or without low back pain were extracted. The PubMed, ScienceDirect, Ovid MEDLINE, Scopus, Springer, and Cumulative Index to Nursing and Allied Health Literature databases were searched from inception to August 2018. Two independent raters appraised the quality of the included studies using the Critical Appraisal Skills Program checklist.ResultsFourteen studies were included. The results revealed significant correlations between US and EMG measures for the lumbar multifidus and erector spinae muscle during most contraction levels and postures. For transverse abdominis and internal oblique, US and EMG measures were correlated during low load abdominal drawing or bracing. The correlations were influenced by trunk position for higher intensities of contraction. For the external oblique muscle, correlation was observed only during trunk rotation.ConclusionChanges in muscle thickness should not be interpreted as muscle activity for all tasks, positions, and contraction types. Only during prime movement tasks performed with isometric contraction could muscle thickness change be considered as muscle activity. Also, upright postures influenced the relationship between changes in muscle thickness and muscle activity for abdominal muscles.     

Examination of the flexion relaxation phenomenon in erector spinae muscles during short duration slumped sitting

OBJECTIVE: The purpose of this study was to examine the myoelectric activity of the erector spinae muscles of the back in order to determine if the flexion relaxation phenomenon occurs in seated forward flexion or slumped postures. BACKGROUND: The flexion relaxation phenomenon during standing forward flexion is well documented. However, flexion relaxation in seated forward flexion has not been studied. It is possible that flexion relaxation could be linked with low back pain that some individuals experience during seated work. METHODS: Twenty-two healthy subjects (11 males, 11 females) participated in the study. Surface electromyography was used to measure the level of muscle activity at the thoracic and lumbar levels of the erector spinae muscles. An electromagnetic tracking device measured the three-dimensional movement of the lumbar spine. Five trials each of standing and seated forward flexion were performed. RESULTS: A slumped sitting posture yielded flexion relaxation of the thoracic erector spinae muscles, whereas the lumbar erector spinae muscle group remained at relatively constant activation levels regardless of seated posture. Thoracic erector spinae silence occurred at a smaller angle of lumbar flexion during sitting than the flexion relaxation angle observed during standing flexion relaxation. CONCLUSIONS: Since the myoelectric activity of the lumbar erector spinae did not increase, it is likely that the passive tissues of the vertebral column were loaded to support the moment at L4/L5. Ligaments contain a large number of free nerve endings which act as pain receptors and therefore could be a potential source of low back pain during seated work. RELEVANCE: Examination of flexion relaxation during seated postures may provide insight into the association between low back pain and seated work.     

脑卒中偏瘫患者在坐位躯干旋转时躯干肌群表面肌电信号特征研究

目的:比较正常人及脑卒中偏瘫患者在躯干向左(瘫痪侧)及向右(非瘫痪侧)旋转过程中躯干浅表肌群的表面肌电信号特征。方法:选取17例脑卒中偏瘫患者及16例健康志愿者,采集2组受试者在躯干左旋(向瘫痪侧旋转)45°、右旋(向非瘫痪侧旋转)45°时腹直肌、腹外斜肌、胸段竖脊肌、腰段竖脊肌、背阔肌的表面肌电图均方根振幅(RMS)。结果:正常人在躯干向一侧旋转时对侧腹外斜肌RMS值大于转向侧(P0.01),转向侧胸段竖脊肌、背阔肌的RMS值大于对侧(P0.01);向左(瘫痪侧)旋转时脑卒中患者偏瘫侧腹外斜肌、胸段竖脊肌和背阔肌的RMS值低于正常组左侧(P0.01),非瘫痪侧腹外斜肌的RMS值低于正常组右侧(P0.01);向右(非瘫痪侧)旋转时脑卒中患者偏瘫侧腹外斜肌、胸段竖脊肌的RMS值小于正常组左侧(P0.01),偏瘫侧腰段竖脊肌的RMS值小于正常组左侧(P0.05),非瘫痪侧腹外斜肌、腰段竖脊肌和胸段竖脊肌的RMS值小于正常组右侧(P0.01)。结论:正常人在躯干旋转时胸段竖脊肌、背阔肌、腹外斜肌呈现明显的交叉性,转向侧的胸段竖脊肌、背阔肌的肌电活动明显增加,对侧的腹外斜肌肌电活动明显增加;而脑卒中患者则没有这种交叉性。     

Prevalence and sensitivity of trigger points in lumbo-pelvic-hip muscles in patients with patellofemoral pain syndrome

ObjectivesChanges in the activity of the lumbo-pelvic-hip muscles have been established as a major cause of patellofemoral pain syndrome (PFPS), a common orthopedic problem. The present study aimed to compare the prevalence and sensitivity of myofascial trigger points (MTrPs) in lumbo-pelvic-hip muscles in persons with and without PFPS.MethodsThirty women with PFPS and 30 healthy women 18–40 years old were recruited for this study. The prevalence of MTrPs was assessed by palpation, and pressure algometry was used to measure the pressure pain threshold. This study evaluated the areas where MTrPs are most commonly found in the lumbar muscles (internal oblique, erector spinae and quadratus lumborum), pelvic muscles (gluteus maximus, gluteus medius, gluteus minimus and piriformis), and hip muscles (hip adductor, quadriceps, hamstring, tensor fascia lata and sartorius). Independent t-tests were used to compare mean pressure pain thresholds between the two groups. Chi-squared tests were used to compare the prevalence of MTrPs.ResultsThe prevalence of MTrPs was significantly higher in most of the lumbo-pelvic-hip muscles in patients with PFPS compared to healthy persons. However, there were no significant differences between groups in the prevalence of MTrPs in the gluteus minimus or adductor muscles. The pressure pain threshold in lumbo-pelvic-hip muscles was lower in patients with PFPS compared to healthy participants.ConclusionIn patients with PFPS the prevalence of MTrPs in the lumbo-pelvic-hip region was higher, and the pressure pain threshold was lower, than in healthy people. Thus therapy to treat PFPS should target the lumbo-pelvic-hip muscles.     

Muscle fatigue in the gluteus maximus changes muscle synergies during single-leg landing

IntroductionHamstring strain often occurs at the end of a match or during practice in sports activities. The gluteus maximus muscle is an important muscle for hip extension along with the hamstring. Gluteus maximus muscle dysfunction may be involved in the occurrence of hamstring strain. Therefore, we focused on gluteus maximus muscle fatigue and investigated gluteus maximus and hamstring coordination.MethodsHe activities of the right side of the erector spinae, internal oblique, upper, and lower gluteus maximus fibers, gluteus medius, rectus femoris, semitendinosus, and medial head of the gastrocnemius muscle were measured in 21 young healthy men during single-leg landing before and after fatigue intervention. Fatigue intervention of the gluteus maximus muscle was performed using electrical muscle stimulation. Electromyography data were analyzed using non-negative matrix factorization. Additionally, to evaluate gluteus maximus fatigue, an isometric hip extension strength test and frequency analysis were performed before and after the intervention.ResultsThe isometric strength power and median frequency significantly decreased after intervention. Two muscle synergies were extracted and the contribution of semitendinosus of a synergy that was activated just before landing, significantly increased due to the intervention.DiscussionThe results of the isometric hip strength test and frequency analysis, the gluteus maximus fatigued by the intervention. The hip extensor muscles eccentrically contract to absorb the ground reaction force during landing. Therefore, our results may suggest that the eccentric load increases for the hamstring due to gluteus maximus muscle fatigue and may be a risk factor for hamstring strain.     

Association of sagittal spinal alignment in the sitting position with the trunk and lower extremity muscle masses in children and adults with cerebral palsy: A pilot study

BackgroundWe examined the association of sagittal spinal alignment in the sitting position with the trunk and lower extremity muscle masses in children and adults with cerebral palsy (CP). We also compared muscle masses between children and adults with CP who could and could not sit without the support of their upper extremities.MethodsThe subjects were 34 children and adults with CP. Sagittal spinal alignment in the sitting position, such as thoracic kyphosis, lumbar lordosis, and sacral anterior inclination angles were measured using a Spinal Mouse. The thicknesses of the trunk and lower extremity muscles were measured using an ultrasound imaging device. Furthermore, the subjects were classified into the sitting-possible group (n = 18), who could sit without the support of the upper extremities, or a sitting-impossible group (n = 16), who could not sit without the support of the upper extremities.FindingsStepwise regression analysis revealed that the lumbar multifidus muscle thickness and body weight were significant and independent factors of the lumbar lordosis angle in the sitting position. The thicknesses of the thoracic erector spinae, gluteus maximus and minimus, long head of the biceps femoris, semitendinosus, and rectus femoris muscles were significantly lower in the sitting-impossible group than those in the sitting-possible group.InterpretationDecreased lumbar lordosis angle in the sitting position was associated with decreased lumbar multifidus muscle mass in children and adults with CP. Furthermore, not only trunk extensor but also hip joint muscles may contribute to sitting without upper extremity support.     

Neuromuscular control of walking with chronic low-back pain

The reported association of low-back pain and musculoskeletal disorders contributed to the examination of the lumbar spine and hip extensor activation patterns in back pain sufferers during walking. Seventeen idiopathic low-back pain male subjects and 16 healthy volunteers participated in the study. Hip joint ROMs in the sagittal plane and neuromuscular activities of erector spinae [L3, T12], gluteus maximus and biceps femoris were recorded on one randomly selected body side in each group. Analysis using the Student's t-test revealed significant differences for hip joint range of motion, stride time and significantly earlier onsets of the lumbar spine and hip extensors of the back pain sufferers compared with the healthy controls. It is assumed, that low-back disorders are related to changes of the lumbar spine and hip extensor recruitment pattern.     

Normative parameters and anthropometric variability of lumbar muscle stiffness using ultrasound shear-wave elastography

BackgroundQuantifying stiffness of the lumbar spine musculature using shear-wave elastography (SWE) maybe beneficial in the diagnosis and treatment of non-specific low back pain (LBP). The primary purpose of this study was to establish normative parameter and variance estimates of lumbar spine muscle stiffness at rest and during submaximal contraction levels using SWE in healthy individuals. A second aim was to determine the relationship between lumbar spine muscle stiffness and a variety of demographic, anthropometric, and medical history variables.MethodsThis cross-sectional study included stiffness measurements of the lumbar musculature in 120 asymptomatic individuals using ultrasound SWE. The lumbar erector spinae muscle was measured during rest only and lumbar multifidus muscle was measured during rest and during submaximal contraction using a prone contralateral arm lift. Statistical comparisons of shear modulus were made between sex (male vs. female) and muscle condition (erector spinae rest, lumbar multifidus rest, lumbar multifidus contracted) using 2 × 3 repeated measures analysis of variance (ANOVA). Univariate associations between shear modulus and age, sex, BMI, activity level, and history of back pain were assessed using correlation analysis.FindingsShear modulus at rest was approximately 4 kPa for the erector spinae muscles and approximately 6 kPa for the lumbar multifidus muscles. Shear modulus substantially increased during contraction, and varied by sex, BMI, and self-reported activity level, with men and more active individuals generally having stiffer muscles.InterpretationVariability in shear modulus of the lumbar musculature may be mediated through a combination of muscle size and contractile state, which is consistent with our findings of higher stiffness in the more postural lumbar multifidi muscles, during contraction, and in larger and more active individuals. These findings should inform and be accounted for in future comparative clinical studies.     

Influence of Hip Joint Position on Muscle Activity during Prone Hip Extension with Knee Flexion

[Purpose] This study investigated the selective activation of the gluteus maximus during a prone hip extension with knee flexion exercise, with the hip joint in different positions. [Subjects] The subjects were 21 healthy, male volunteers. [Methods] Activities of the right gluteus maximus, right hamstrings, bilateral lumbar erector spinae, and bilateral lumbar multifidus were measured using surface electromyography during a prone hip extension with knee flexion exercise. Measurements were made with the hip joint in each of 3 positions: (1) a neutral hip joint position, (2) an abduction hip joint position, and (3) an abduction with external rotation hip joint position. [Results] Gluteus maximus activity was significantly higher when the hip was in the abduction with external rotation hip joint position than when it was in the neutral hip joint and abduction hip joint positions. Gluteus maximus activity was also significantly higher in the abduction hip joint position than in the neutral hip joint position. Hamstring activity was significantly lower when the hip was in the abduction with external rotation hip joint position than when it was in the neutral hip joint and abduction hip joint positions. [Conclusion] Abduction and external rotation of the hip during prone hip extension with knee flexion exercise selectively activates the gluteus maximus.Key words: Prone hip extension with knee flexion, Hip joint position, Electromyography