The gluteus maximus is considered to be an important muscle for

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1 DAVID M. SELKOWITZ, PT, PhD, DPT, OCS, DAAPM 1 GEORGE J. BENECK, PT, PhD, OCS, KEMG 2 CHRISTOPHER M. POWERS, PT, PhD, FACSM, FAPTA 3 Comparison of Electromyographic Activity of the Superior and Inferior Portions of the Gluteus Maximus Muscle During Common Therapeutic Exercises The gluteus maximus is considered to be an important muscle for lower extremity function and has been referred to as a hallmark of bipedalism and erect posture in humans. 28 The gluteus maximus is a relatively large muscle, with fibers that are both broad (large cross-sectional area) and long. 31 Considered in its entirety, the gluteus maximus has been reported to function as an extensor, 13,33 external rotator, 8,13 and abductor of the hip joint. 33 TTSTUDY DESIGN: Controlled laboratory study, repeated-measures design. TTBACKGROUND: Previous studies have reported that the superior and inferior portions of the gluteus maximus have different functional roles. Knowledge of how the different portions of the gluteus maximus are activated during therapeutic exercise may lead to more specific exercise prescription. TTOBJECTIVE: To compare muscle activation of the superior and inferior portions of the gluteus maximus during commonly used therapeutic exercises. TTMETHODS: Twenty healthy persons participated. Electromyographic (EMG) signals were obtained from the superior and inferior portions of the gluteus maximus using fine-wire electrodes. Normalized EMG signal amplitudes were compared between the superior and inferior gluteus maximus across 11 exercises using a 2-way repeated-measures analysis of variance. TTRESULTS: The superior portion of the gluteus maximus had significantly greater relative EMG activity than the inferior portion of the gluteus maximus during exercises that incorporated elements of hip abduction and/or external rotation (5 of 11 exercises evaluated). There was no significant difference in activation between the superior and inferior portions of the gluteus maximus during the remaining 6 exercises. TTCONCLUSION: The results of the present study demonstrate preferential activation of the superior portion of the gluteus maximus during exercises that incorporate elements of hip abduction and/ or external rotation. In contrast, exercises that primarily involve hip extension target both portions of the gluteus maximus to a similar extent. J Orthop Sports Phys Ther 2016;46(9): Epub 5 Aug doi: /jospt TTKEY WORDS: electromyography, exercise therapy, gluteal muscles, hip Although the gluteus maximus is a single muscle, studies have reported that there are 2 functionally distinct aspects, the superior and inferior portions. The size of the superior portion of the gluteus maximus is greater than the inferior portion in humans when compared to nonhuman primates. 28 Stern 28 stated that the superior portion of the gluteus maximus is better suited for hip abduction, owing to its insertion into the fascia lata, while the inferior portion is better suited for hip extension, owing to its larger moment arm for this motion. To date, few studies have evaluated the functional actions of the superior and inferior portions of the gluteus maximus. Bartlett et al 2 reported that both portions of the gluteus maximus were more active in sprinting than in running or walking, and more active in climbing than in walking. Pirouzi et al 21 reported that the contralateral superior gluteus maximus was more active than the inferior gluteus maximus during ipsilateral isometric trunk rotation (analogous to contralateral hip external rotation). In a fine-wire electromyography (EMG) study 1 Department of Physical Therapy, MGH Institute of Health Professions, Boston, MA. 2 Department of Physical Therapy, California State University at Long Beach, Long Beach, CA. 3 Jacquelin Perry Musculoskeletal Biomechanics Research Laboratory, Division of Biokinesiology and Physical Therapy, University of Southern California, Los Angeles, CA. This study was approved by the Institutional Review Boards of the Health Sciences Campus of the University of Southern California and Western University of Health Sciences. The authors certify that they have no affiliations with or financial involvement in any organization or entity with a direct financial interest in the subject matter or materials discussed in the article. Address correspondence to Dr David M. Selkowitz, MGH Institute of Health Professions, Department of Physical Therapy, Charlestown Navy Yard, 36 First Avenue, Boston, MA dselkowitz@mghihp.edu t Copyright 2016 Journal of Orthopaedic & Sports Physical Therapy 794 september 2016 volume 46 number 9 journal of orthopaedic & sports physical therapy

2 assessing level walking and stair ascent/ descent, Lyons et al 17 reported that the superior portion of the gluteus maximus was more active as a hip abductor, similar to the gluteus medius, while the inferior portion of the gluteus maximus was more active as a hip extensor. Strengthening of the gluteus maximus has been advocated for rehabilitation programs for various lower extremity disorders, including patellofemoral pain, 10,11,16 hamstring injuries, 30 piriformis syndrome, 29 and Achilles tendinopathy. 12 In particular, control of hip abduction and external rotation is considered an important element of knee rehabilitation. 22 Given the multifunctional role of the gluteus maximus and its 3-D control of the hip joint, it is logical to assume that various exercises intended to focus on the gluteus maximus may target the superior and inferior portions differently. The premise of a functional subdivision within a muscle is supported by studies that have demonstrated task-dependent activation differences of various portions of the trapezius 15 and gluteus medius. 26 Of the studies that have assessed the activity of the gluteus maximus during therapeutic exercises, none have differentially assessed the superior and inferior portions. 1,3-5,18,24,32,34 The purpose of the current study was to compare EMG signal amplitudes of the superior and inferior portions of the gluteus maximus during commonly used therapeutic exercises using fine-wire electrodes. We hypothesized that the superior and inferior portions of the gluteus maximus would be activated differently among different exercises based on the hip motions incorporated within a given exercise. Knowledge of how the different portions of the gluteus maximus are activated during various therapeutic exercises may lead to more specific exercise prescription. METHODS Twenty healthy subjects (10 men, 10 women) between the ages of 18 and 50 years were recruited for this study. Exclusion criteria included the presence of orthopaedic injuries of the trunk or lower extremities, neurologic disorders, or pregnancy. The subjects mean ± SD age, height, and weight were 27.9 ± 6.2 years, ± 11.1 cm, and 67.7 ± 14.1 kg, respectively. Prior to participation, all subjects were provided with a detailed explanation of the study and signed an informed-consent form approved by the Institutional Review Boards of the Health Sciences Campus of the University of Southern California and Western University of Health Sciences. Instrumentation Electromyographic data were collected using an MA300-XVI EMG system (Motion Lab Systems, Inc, Baton Rouge, LA) with the following characteristics: common-mode rejection ratio, greater than 110 db at 65 Hz; MA-416 discrete preamplifiers; gain, 1 khz 20% ± 1%; and input impedance, greater than 1 MΩ. Electromyographic signals were recorded at a sampling rate of 1560 Hz. The fine-wire electrodes consisted of pairs of presterilized, disposable, 50-µm nickel-chromium-alloy wires that were nylon insulated, except for a 2-mm tip at the end that was inserted into the muscle. 19 Disposable, 25-gauge needles were used as cannulas to insert the electrodes through the skin and into the muscles. Procedure The dominant limb (defined as the limb used to kick a ball) was tested for all subjects. The skin over the lateral hip and buttock of the tested limb was cleaned with rubbing alcohol. The fine-wire electrodes were then inserted into the superior and inferior portions of the gluteus maximus muscle, based on the recommendations of Delagi and Perotto 7 and Lyons et al. 17 Briefly, the wire electrodes for the superior gluteus maximus were inserted superior and lateral to the midpoint of a line drawn between the posterior superior iliac spine and the posterior greater trochanter. The wire electrodes for the inferior portion of the gluteus maximus were inserted inferior and medial to the midpoint of the same line, such that it was 2.5 to 5.0 cm above the gluteal fold. Confirmation of electrode placement was made using electrical stimulation as well as observation of the EMG signal during voluntary isometric contractions in the specific directions in which the portions of the muscle are known to act. The reference electrode was placed over the C7 spinous process. Upon verification of an adequate EMG signal for each insertion, maximum voluntary isometric contractions (MVICs) were performed in 4 different positions, in a random order. This was done to ensure that the highest EMG signal amplitude was produced, as the best position for obtaining the maximum EMG signal of the different portions of the gluteus maximus has not been established. The highest value for each portion of the gluteus maximus, regardless of test position, was used for normalization of the EMG signal. 25 For the first MVIC test, hip extension was resisted using a strap across the distal posterior thigh, with the upper body prone on a treatment table, the hip at an angle of 45 of flexion, and the knee at 90 of flexion. For the second MVIC test, hip extension was resisted using a strap across the distal posterior thigh with the subject lying fully prone, with the knee flexed to 90. A third MVIC test was performed in hip abduction while sidelying on the opposite side on the treatment table, with the posterior aspect of the pelvis and scapulae back against an adjacent wall so that the pelvis was perpendicular to the table. In a position of 30 of hip abduction and the knee fully extended, subjects exerted a maximal hip abduction force against a strap across the distal lateral leg (just proximal to the lateral malleolus). The fourth MVIC test was performed in a sidelying position as described above, except that the hip was abducted to 30 and flexed to 45, with the subject exerting a maximal hip abduction and internal rotation force against a strap across the distal lateral leg (as previously journal of orthopaedic & sports physical therapy volume 46 number 9 september

3 described). A long plastic goniometer was used to measure all joint angles. Verbal encouragement was provided to the subjects during each MVIC test. 6 Prior to data collection, subjects were familiarized with the testing protocol and received instruction in and practiced the exercises to ensure proper performance. Following MVIC testing, participants performed 11 exercises in a random order: hip abduction in sidelying, clam with elastic resistance around thighs (clam), bilateral bridge, unilateral bridge, hip extension in quadruped on elbows with knee extending, hip extension in quadruped on elbows with knee flexed, forward lunge with erect trunk (lunge), squat, sidestep with elastic resistance around thighs in a squat position (sidestep), hip hike, and forward step-up (step-up) (see the APPENDIX, available at for illustrations and written descriptions of exercises). A metronome was set at 40 beats per minute to pace each exercise (except for the sidestep, which was paced at 80 beats per minute). Five repetitions of each exercise were performed (except as described for the sidestep in the APPENDIX). There was 1 metronome beat of rest between each repetition, and a 2-minute rest was provided between each exercise. An event marker was manually triggered during each exercise to assist in identifying the beginning and end of each repetition. After completion of the exercises, subjects repeated the MVIC procedures to ensure that the wire electrodes had not been displaced during testing. 23 EMG Analysis The raw EMG data were imported into MATLAB software for processing (The MathWorks, Inc, Natick, MA). Data were band-pass Butterworth filtered (10th order) at 35 to 750 Hz. The low-cut/highpass boundary was slightly higher than that which we had originally intended due to issues involving low-frequency artifact in our laboratory; however, it followed recommended guidelines for considering low-frequency artifact. 20 TABLE Normalized EMG Amplitude of Superior and Inferior Portions of the Gluteus Maximus in Each Exercise* Exercise Superior Gluteus Maximus Inferior Gluteus Maximus Mean Difference P Value Abduction in sidelying 23.7 ± ± (12.3, 24.7) <.001 Bilateral bridge 17.4 ± ± ( 9.9, 0.0).052 Clam 43.6 ± ± (17.9, 40.5) <.001 Hip hike 17.7 ± ± (5.1, 19.5).002 Forward lunge 20.1 ± ± ( 3.1, 6.3).485 Quadruped hip extension with knee extending Quadruped hip extension with knee flexed Abbreviations: EMG, electromyography; MVIC, maximum voluntary isometric contraction. *Values are mean ± SD percent MVIC unless otherwise indicated. Values in parentheses are 95% confidence interval. t test ± ± ( 11.9, 6.4) ± ± ( 13.1, 4.6).328 Sidestep 27.4 ± ± (0.6, 14.3).034 Squat 12.9 ± ± ( 1.3, 6.1).188 Forward step-up 22.8 ± ± (1.2, 13.0).020 Unilateral bridge 34.6 ± ± ( 9.9, 5.7).574 The amplitude of the EMG signal was obtained by deriving the root-meansquare (RMS) of the signal, which was calculated by squaring each data point, averaging data points, and calculating the square root over a 75-millisecond moving window. This resulted in full-wave rectification and smoothing of the raw EMG signal. For statistical comparisons, EMG signal amplitudes during the exercises were expressed as a percentage of EMG obtained during the MVIC. The highest EMG signal amplitude obtained for each portion of the gluteus maximus during any of the 4 MVIC tests was used for normalization. The highest EMG signal was defined as the highest mean RMS obtained over a consecutive 1-second period during the MVIC. 25 The primary dependent variable of interest was the mean RMS (percent MVIC) of the EMG signal from each portion of the gluteus maximus during each exercise. This included the concentric and eccentric phases of each exercise. After obtaining the mean RMS for each repetition of an exercise, the mean of the 5 repetitions was used for statistical analysis. Visual inspection of the recorded signal was used as the reference standard to determine the beginning and end of the exercise contractions, 14 and was aided by the event marker described previously. Statistical Analysis A 2-by-11 analysis of variance was used to compare EMG signal amplitudes between the superior and inferior portions of the gluteus maximus across the 11 exercises. In case of a significant muscleby-exercise interaction, paired t tests (2-tailed) were used to compare the superior and inferior portions of the gluteus maximus within each exercise. The alpha level was set at.05. All statistical analyses were performed in SPSS software (IBM Corporation, Armonk, NY). RESULTS A significant muscle-by-exercise interaction was found (P<.001). Data sphericity was not assumed; therefore, the Greenhouse-Geisser correction was used. Pairwise comparisons between the 2 portions of the gluteus maximus within each exercise revealed that activation of the superior gluteus 796 september 2016 volume 46 number 9 journal of orthopaedic & sports physical therapy

4 maximus was significantly greater than that of the inferior gluteus maximus during the hip abduction in sidelying, clam, hip hike, sidestep, and step-up exercises (TABLE). There was no significant difference between the 2 portions of the gluteus maximus for the remaining 6 exercises (TABLE). DISCUSSION The purpose of the current study was to compare EMG amplitudes of the superior and inferior portions of the gluteus maximus in healthy individuals during commonly used therapeutic exercises. Our results demonstrate that the superior and inferior portions of the gluteus maximus were activated differently among several of the exercises examined. In total, 5 of the exercises elicited significantly greater EMG activity in the superior portion of the gluteus maximus compared to the inferior portion, while both portions of the gluteus maximus were equally activated during the remaining exercises evaluated. Differences in activation of the 2 portions of the gluteus maximus were evident in the exercises that incorporated hip motions other than extension. For example, superior gluteus maximus EMG activity was greater than that of the inferior gluteus maximus in the exercises that incorporated hip abduction and/or external rotation movements (ie, sidelying hip abduction, clam, standing hip hike, sidestep, and forward step-up). Both the inferior and superior portions of the gluteus maximus were equally activated during exercises that primarily involved hip extension motions (ie, quadruped hip extension with the knee flexed and with the knee extending, unilateral and bilateral bridging, squat, and forward lunge). The superior gluteus maximus exhibited the highest EMG signal amplitude during the clam exercise (43.6% MVIC). This is logical, given that this exercise primarily involves abduction and external rotation motions. Other exercises that resulted in superior gluteus maximus amplitudes of 30% MVIC or greater included the unilateral bridge and hip extension in quadruped on elbows with the knee flexed. It should be noted, however, that these exercises primarily involved the motion of hip extension. The inferior portion of the gluteus maximus exhibited its highest EMG signal amplitude during the unilateral bridge exercise (36.7% MVIC). This exercise primarily involves hip motion in the sagittal plane. The exercises with the next highest EMG amplitudes were the hip extension in quadruped on elbows with knee flexed (34.3% MVIC) and hip extension in quadruped on elbows with knee extending (31.2% MVIC), both of which involve hip extension as the primary motion. Overall, our results appear to support the concept of a functional differentiation of the superior and inferior gluteus maximus. More specifically, our data indicate that the superior portion is active as a hip extensor, abductor, and external rotator, and the inferior portion is active primarily as a hip extensor. Our findings are in agreement with those of Lyons et al, 17 who reported that the superior gluteus maximus functions more as a hip abductor and that the inferior gluteus maximus functions more as a hip extensor. In addition, Pirouzi et al 21 demonstrated a greater hip external rotation function of the superior gluteus maximus than of the inferior gluteus maximus, which is in agreement with our findings. It is important to note that other hip abductor muscles, such as the gluteus medius and tensor fascia lata, have been shown to be more active than the superior gluteus maximus during selected therapeutic exercises emphasizing hip abduction (eg, sidelying hip abduction, standing hip hike). 25 Our results may assist in identifying more specific rehabilitation exercises for the gluteus maximus. For example, patients with conditions associated with excessive hip adduction and internal rotation (eg, patellofemoral pain, femoral acetabular impingement) may benefit from exercises that better target the superior portion of the gluteus maximus, while patients with conditions such as hamstring strains may benefit from exercises that better target the entire gluteus maximus. Further research is needed to delineate the functions of the gluteus maximus in various functional exercises and movements in persons with lower extremity conditions. Activation differences were observed between the upper and lower portions of the gluteus maximus, even though the entire muscle is innervated by the inferior gluteal nerve. This finding is consistent with what has been reported for other muscles with highly variable fiber orientations (ie, the trapezius and gluteus medius). 15,26 It is possible that the variable activation patterns observed between the 2 portions of the gluteus maximus during the exercises studied may have been the result of nonuniform distribution and/or asynchronous recruitment of motor units throughout the muscle. Neuromuscular compartments consisting of subpopulations of motor units that may be selectively activated under certain conditions and activities have been identified in other muscles. 15 In the current study, there was considerable variability among study participants. For example, not all individuals demonstrated activation patterns consistent with the reported mean data for the entire cohort. Such variability is common among EMG studies, however, 3,9,27 and care should be taken to avoid overgeneralizing the findings reported in the current study. In addition, the influence of pain and/or pathology on activation of the different portions of the gluteus maximus remains to be seen and should be the focus of future investigations. A limitation of the current study is the absence of kinematic data. These data may provide more specific information regarding the component motions of each exercise. In addition, the subject sample was a young, healthy cohort. Electromyographic signal amplitude between the 2 portions of the gluteus maximus journal of orthopaedic & sports physical therapy volume 46 number 9 september

5 might differ in persons with lower extremity pathology or pain. CONCLUSION The results of the current study demonstrated that the superior portion of the gluteus maximus exhibited significantly greater EMG amplitude than the inferior portion during exercises that incorporated hip abduction and external rotation. In contrast, exercises that primarily involved hip extension targeted both portions of the gluteus maximus to a similar extent. Electromyographic amplitude was greatest for the superior gluteus maximus during the clam exercise, while the inferior gluteus maximus demonstrated its greatest EMG signal during the unilateral bridge exercise. t KEY POINTS FINDINGS: The superior portion of the gluteus maximus muscle was activated to a significantly greater extent than the inferior portion in exercises that incorporate hip abduction and external rotation movements. Both portions of the gluteus maximus were activated to a similar extent during exercises that primarily consisted of hip extension. IMPLICATIONS: Our results may assist in identifying more specific rehabilitation exercises for the gluteus maximus. CAUTION: This study was conducted using a sample of healthy, pain-free individuals. Results may differ in persons with various musculoskeletal disorders. ACKNOWLEDGMENTS: We thank Dr Lucinda Baker, PT, PhD, for her consultation on the EMG analysis, and Mr Jess Lopatynski for his assistance with the photography. REFERENCES 1. Ayotte NW, Stetts DM, Keenan G, Greenway EH. Electromyographical analysis of selected lower extremity muscles during 5 unilateral weight-bearing exercises. J Orthop Sports Phys Ther. 2007;37: jospt Bartlett JL, Sumner B, Ellis RG, Kram R. Activity and functions of the human gluteal muscles in walking, running, sprinting, and climbing. Am J Phys Anthropol. 2014;153: org/ /ajpa Bolgla LA, Uhl TL. Electromyographic analysis of hip rehabilitation exercises in a group of healthy subjects. J Orthop Sports Phys Ther. 2005;35: jospt Boren K, Conrey C, Le Coguic J, Paprocki L, Voight M, Robinson TK. Electromyographic analysis of gluteus medius and gluteus maximus during rehabilitation exercises. Int J Sports Phys Ther. 2011;6: Cambridge ED, Sidorkewicz N, Ikeda DM, McGill SM. Progressive hip rehabilitation: the effects of resistance band placement on gluteal activation during two common exercises. Clin Biomech (Bristol, Avon). 2012;27: org/ /j.clinbiomech Campenella B, Mattacola CG, Kimura IF. Effect of visual feedback and verbal encouragement on concentric quadriceps and hamstrings peak torque of males and females. Isokinet Exerc Sci. 2000;8: Delagi EF, Perotto A. Anatomic Guide for the Electromyographer: The Limbs. 2nd ed. Springfield, IL: Charles C. Thomas; Delp SL, Hess WE, Hungerford DS, Jones LC. Variation of rotation moment arms with hip flexion. J Biomech. 1999;32: DiStefano LJ, Blackburn JT, Marshall SW, Padua DA. Gluteal muscle activation during common therapeutic exercises. J Orthop Sports Phys Ther. 2009;39: org/ /jospt Earl JE, Hoch AZ. A proximal strengthening program improves pain, function, and biomechanics in women with patellofemoral pain syndrome. Am J Sports Med. 2011;39: Ferber R, Kendall KD, Farr L. Changes in knee biomechanics after a hip-abductor strengthening protocol for runners with patellofemoral pain syndrome. J Athl Train. 2011;46: Franettovich Smith MM, Honeywill C, Wyndow N, Crossley KM, Creaby MW. Neuromotor control of gluteal muscles in runners with Achilles tendinopathy. Med Sci Sports Exerc. 2014;46: MSS Goss CM, ed. Gray s Anatomy. 29th ed. Philadelphia, PA: Lea & Febiger; Hodges PW, Bui BH. A comparison of computerbased methods for the determination of onset of muscle contraction using electromyography. Electroencephalogr Clin Neurophysiol. 1996;101: Holtermann A, Roeleveld K, Mork PJ, et al. Selective activation of neuromuscular compartments within the human trapezius muscle. J Electromyogr Kinesiol. 2009;19: org/ /j.jelekin Khayambashi K, Mohammadkhani Z, Ghaznavi K, Lyle MA, Powers CM. The effects of isolated hip abductor and external rotator muscle strengthening on pain, health status, and hip strength in females with patellofemoral pain: a randomized controlled trial. J Orthop Sports Phys Ther. 2012;42: org/ /jospt Lyons K, Perry J, Gronley JK, Barnes L, Antonelli D. Timing and relative intensity of hip extensor and abductor muscle action during level and stair ambulation. An EMG study. Phys Ther. 1983;63: McBeth JM, Earl-Boehm JE, Cobb SC, Huddleston WE. Hip muscle activity during 3 sidelying hip-strengthening exercises in distance runners. J Athl Train. 2012;47: Mulroy SJ, Farrokhi S, Newsam CJ, Perry J. Effects of spinal cord injury level on the activity of shoulder muscles during wheelchair propulsion: an electromyographic study. Arch Phys Med Rehabil. 2004;85: org/ /j.apmr Perry J. The contribution of dynamic electromyography to gait analysis. In: DeLisa JA, ed. Gait Analysis in the Science of Rehabilitation. Baltimore, MD: US Department of Veterans Affairs; 1998: Pirouzi S, Hides J, Richardson C, Darnell R, Toppenberg R. Low back pain patients demonstrate increased hip extensor muscle activity during standardized submaximal rotation efforts. Spine (Phila Pa 1976). 2006;31:E999- E brs d 22. Powers CM. The influence of abnormal hip mechanics on knee injury: a biomechanical perspective. J Orthop Sports Phys Ther. 2010;40: jospt Powers CM. Patellar kinematics, part I: the influence of vastus muscle activity in subjects with and without patellofemoral pain. Phys Ther. 2000;80: Reiman MP, Bolgla LA, Loudon JK. A literature review of studies evaluating gluteus maximus and gluteus medius activation during rehabilitation exercises. Physiother Theory Pract. 2012;28: Selkowitz DM, Beneck GJ, Powers CM. Which exercises target the gluteal muscles while minimizing activation of the tensor fascia lata? Electromyographic assessment using finewire electrodes. J Orthop Sports Phys Ther. 2013;43: jospt Semciw AI, Pizzari T, Murley GS, Green RA. Gluteus medius: an intramuscular EMG investigation of anterior, middle and posterior segments during gait. J Electromyogr Kinesiol. 2013;23: jelekin Sidorkewicz N, Cambridge ED, McGill SM. 798 september 2016 volume 46 number 9 journal of orthopaedic & sports physical therapy

6 Examining the effects of altering hip orientation on gluteus medius and tensor fascae [sic] latae interplay during common non-weight-bearing hip rehabilitation exercises. Clin Biomech (Bristol, Avon). 2014;29: org/ /j.clinbiomech Stern JT, Jr. Anatomical and functional specializations of the human gluteus maximus. Am J Phys Anthropol. 1972;36: org/ /ajpa Tonley JC, Yun SM, Kochevar RJ, Dye JA, Farrokhi S, Powers CM. Treatment of an individual with piriformis syndrome focusing on hip muscle strengthening and movement reeducation: a case report. J Orthop Sports Phys Ther. 2010;40: jospt Wagner T, Behnia N, Ancheta WK, Shen R, Farrokhi S, Powers CM. Strengthening and neuromuscular reeducation of the gluteus maximus in a triathlete with exercise-associated cramping of the hamstrings. J Orthop Sports Phys Ther. 2010;40: jospt Ward SR, Winters TM, Blemker SS. The architectural design of the gluteal muscle group: implications for movement and rehabilitation. J Orthop Sports Phys Ther. 2010;40: Willcox EL, Burden AM. The influence of varying hip angle and pelvis position on muscle recruitment patterns of the hip abductor EARN CEUs With JOSPT s Read for Credit Program JOSPT s Read for Credit (RFC) program invites readers to study and analyze selected JOSPT articles and successfully complete online exams about them for continuing education credit. To participate in the program: 1. Go to and click on Read for Credit in the top blue navigation bar that runs throughout the site. 2. Log in to read and study an article and to pay for the exam by credit card. 3. When ready, click Take Exam to answer the exam questions for that article. 4. Evaluate the RFC experience and receive a personalized certificate of continuing education credits. The RFC program offers you 2 opportunities to pass the exam. You may review all of your answers including your answers to the questions you missed. You receive 0.2 CEUs, or 2 contact hours, for each exam passed. during the clam exercise. J Orthop Sports Phys Ther. 2013;43: org/ /jospt Williams P, ed. Gray s Anatomy. 38th ed. Edinburgh, UK: Churchill Livingstone; Youdas JW, Foley BM, Kruger BL, et al. Electromyographic analysis of trunk and hip muscles during resisted lateral band walking. Physiother Theory Pract. 2013;29: org/ / MORE INFORMATION JOSPT s website maintains a history of the exams you have taken and the credits and certificates you have been awarded in My CEUs and Your Exam Activity, located in the right rail of the Read for Credit page listing available exams. journal of orthopaedic & sports physical therapy volume 46 number 9 september

7 APPENDIX EXERCISES PERFORMED IN THE STUDY* Exercise Description Image Hip abduction in sidelying Clam in sidelying, with elastic resistance around thighs Bilateral bridge Unilateral bridge Starting position was lying on a treatment table on the side opposite the tested limb. The table was placed along a wall. The lower extremity on the table was flexed to 45 at the hip and 90 at the knee. The subject s back and plantar surface of the foot were against the wall for control of position and movement. The subject then abducted the tested hip to approximately 30 and then returned the limb to the table. To control for the correct movement, the subject kept the heel in light contact with the wall (via a towel), while sliding it along the wall, with the toes pointed horizontally away from the wall. Starting position was lying on a treatment table on the side opposite the tested limb. The table was placed along a wall. Both limbs were flexed to 45 at the hip and 90 at the knee, with the tested limb on top of the other limb. The subject s back and plantar surface of the foot were placed against the wall for control of position and movement. The subject raised the tested limb s knee off the other limb, such that the hip was in 30 of abduction, before returning to the starting position, while keeping both heels in contact with each other and the wall. Subjects performed this activity with bluecolored Thera-Band (The Hygenic Corporation, Akron, OH) tubing around the distal thighs, with no stretch or slack on the tubing prior to raising the limb. The elastic resistance was used because the motion involved is a multiplanar arc that is only minimally resisted by gravity. Starting position was hook-lying with the knees at 90 of flexion, hips at 45 of flexion, 0 of rotation and abduction, trunk in neutral, and feet flat on the table. The subject then pushed both feet into the table to raise the pelvis until a position of 90 of knee flexion and 0 of hip flexion was achieved bilaterally before returning to the starting position. The hips remained at 0 of rotation and abduction during the exercise, with the trunk in neutral. Starting position was unilateral hook-lying, as that described for the bilateral bridge, except that the nontested lower limb remained on the table (0 at the hip and knee). The subject then pushed with the tested limb s foot into the table to raise the pelvis until a position of 90 of knee flexion and 0 of hip flexion was achieved ipsilaterally, before returning to the starting position. The nontested lower limb moved up and down with the pelvis, without changing the positions of its joints. The hips remained at 0 of rotation and abduction during the exercise, with the pelvis and trunk in neutral. Hip extension in quadruped on elbows with knee extending Starting position was quadruped, with the upper body supported by the elbows and forearms, and the knees and elbows at approximately 90 of flexion. The subject then lifted the tested lower limb up and backward, extending the hip and knee to 0, and then returned to the starting position. journal of orthopaedic & sports physical therapy volume 46 number 9 september 2016 B1

8 APPENDIX Exercise Description Image Hip extension in quadruped on elbows with knee flexed This exercise was performed in the same manner as described for quadruped with knee extending, except that the subject maintained the knee in 90 of flexion throughout the exercise. Forward lunge with erect trunk Squat Starting position was standing with the knees and hips at 0 in the sagittal and coronal planes, with the feet/toes pointed straight ahead in midline. The subject then stepped forward with the tested limb to position it at 90 of knee and hip flexion, with the other limb at 90 of knee flexion and 0 at the hip (knee not contacting the floor). The knees moved over the second toe of the ipsilateral limb so that the limbs moved in the sagittal plane. The floor was marked to facilitate correct foot and knee placement, and a pillow was placed as a contact guide for the knee of the nontested limb. Starting position was standing with the knees and hips at 0 in the sagittal plane, with slight hip external rotation, such that the feet/ toes pointed laterally from midline approximately 15. The distance between the feet in the coronal plane was two thirds of the length from the greater trochanter to the floor (measured in the erect standing position), so that the hips were in slight abduction. Subjects then squatted so that the knees and hips were at approximately 90 of flexion, with the knees moving in a direction parallel to the toes (ie, over the second toe of the ipsilateral limb). B2 september 2016 volume 46 number 9 journal of orthopaedic & sports physical therapy

9 APPENDIX Exercise Description Image Sidestep with elastic resistance around the thighs in a squat position Hip hike Starting position was in a squat position, as described above for the squat. The subject then stepped to the side with one limb, followed in the same direction by the other limb, both step lengths approximately 50% of the starting-position distance between the feet (see squat). Knees were kept aligned with the ipsilateral second toe. If a sidestep with each limb in succession was considered a stride, then the subject performed a total of 2 strides in one direction, followed by 2 strides in the opposite direction to return to the starting position. This activity cycle was performed a total of 3 times. The same method of elastic resistance was used in this exercise as in the clam exercise, because there was otherwise little resistance to the sideways movement. Starting position was standing on an elevated platform, with the knees and hips at 0 in the sagittal and coronal planes and the feet/toes pointed straight ahead in midline. The subject remained weight bearing on the tested lower limb, while alternately raising and lowering the other limb off the edge of the platform (by raising and lowering the pelvis), maintaining the knees at 0. journal of orthopaedic & sports physical therapy volume 46 number 9 september 2016 B3

10 APPENDIX Exercise Description Image Forward step-up Starting position was with the foot of the tested limb on a step, at a height resulting in approximately 90 of knee flexion with the tibia vertical. The subject then pushed the tested foot down on the step to raise the nontested foot off the floor to the level of the step, without resting the nontested foot on the step. At this point, the subject was in unilateral weight bearing on the tested limb such that the tested limb s knee and hip were both at 0, with the trunk erect. The subject then returned to the starting position. During the entire exercise, the body was maintained in the sagittal plane, with the tested limb s knee over the ipsilateral toes. *Reprinted with permission from Selkowitz et al. 25 B4 september 2016 volume 46 number 9 journal of orthopaedic & sports physical therapy