Not All Hip Abductions Are Equal: The 45° Paradox Between Gluteus Medius and Tensor Fasciae Latae

Not All Hip Abductions Are Equal: The 45° Paradox Between Gluteus Medius and Tensor Fasciae Latae | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Not All Hip Abductions Are Equal: The 45° Paradox Between Gluteus Medius and Tensor Fasciae Latae Alexandre Maia Farias, Leon Claudio Pinheiro Leal, Renan Wallace Guimarães da Rocha, and 1 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-8523653/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Understanding how joint position influences muscle recruitment is essential for improving exercise prescription. This study examined how different hip flexion angles affect the electromyographic (EMG) activity of the gluteus medius (GMed) and tensor fasciae latae (TFL) during seated hip abduction — a popular movement in resistance training and rehabilitation. Fourteen recreationally trained volunteers performed the exercise at 45°, 90°, and 135° of hip flexion, with the load set at 60% of their individual six-repetition maximum (6RM). Surface EMG signals of GMed and TFL were recorded and normalized to maximal voluntary isometric contraction (%MVIC). Data were analyzed using Friedman’s test and Dunn’s post hoc comparisons (p < 0.05), with effect sizes (Hedges’ g) and 95% confidence intervals calculated via the Estimation Stats platform. Results showed a clear pattern: increased hip flexion significantly decreased TFL activation while maintaining moderate GMed activity. Peak and average GMed activation were notably higher at 45° compared to 135° (p < 0.001), whereas TFL activation decreased progressively across 45°, 90°, and 135° (all p < 0.01). Most importantly, the GMed:TFL activation ratio tripled at 135°, indicating a significant shift toward targeted GMed recruitment and reduced TFL dominance. Therefore, increasing hip flexion during seated abduction enhances the neuromuscular selectivity of the gluteus medius while reducing tensor fasciae latae overactivation — a finding with direct implications for both hypertrophy-focused training and clinical rehab. These findings redefine how a simple change in hip angle can transform one of the most common lower-body exercises. gluteus medius tensor fasciae latae hip abduction electromyography resistance training Figures Figure 1 Figure 2 Figure 3 Figure 4 INTRODUCTION Skill and proficiency in performing sports, occupational, and functional activities rely on the coordinated action of agonist and antagonist muscles, as well as those that stabilize the musculoskeletal system. This coordination ensures efficient movement and helps prevent injuries caused by joint instability. Neuromuscular control of the lower-limb muscles is essential for daily activities like walking, sitting, and standing, as well as for athletic tasks such as jumping and running.⁽¹⁾ Intrinsic deficits in motor control of the lower-limb girdle can cause abnormal force distribution at the hip, affecting both the lower and upper kinetic chains and potentially leading to biomechanical and clinical problems over time.⁽¹⁾ Weakness in the hip muscles, especially the hip abductors and external rotators, has been identified as a key factor in developing pelvic and lower-limb pathologies.⁽²⁻⁴⁾ The gluteus medius (GMed) is a crucial stabilizer of the pelvis and a controller of femoral movement during single-leg tasks.⁽⁵⁾ This pelvic control is vital for limiting hip adduction during gait.⁽⁶,¹⁾ Anatomically, the GMed comprises anterior, middle, and posterior fiber groups, all of which aid in hip abduction. However, based on their anatomical position, the anterior fibers assist with hip flexion and internal rotation, while the posterior fibers support hip extension and external rotation.⁽¹⁾ During single-leg stance, weakness in the GMed can increase compressive and shear forces on the patellofemoral joint due to greater hip adduction.⁽²⁾ This increase appears to be a risk factor for patellofemoral pain,⁽²⁻⁴⁾ knee osteoarthritis,⁽⁷⁾ anterior cruciate ligament injury,⁽²⁾ and iliotibial band syndrome.⁽⁸,⁹⁾ Another key muscle in lower-limb movement is the tensor fasciae latae (TFL), which, in addition to aiding in hip abduction, also supports hip flexion and internal rotation.⁽¹⁰,¹¹⁾ Sahrmann⁽¹²⁾ proposed that a dominance of TFL force over GMed during hip abduction might cause excessive internal rotation during single-limb support tasks. Weaknesses in GMed may result in increased TFL activation and overactivity.⁽⁸,²⁾ This imbalance could contribute to lower limb orthopedic issues, including patellar lateralization caused by excess tension transmitted from the TFL through the iliotibial tract to the knee's lateral retinacula.⁽¹³,¹,¹⁴⁾ Using strength exercises that promote greater GMed activation relative to TFL—measured by the GMed:TFL ratio⁽¹⁵⁻¹⁷⁾—is a common resistance training method for strengthening the GMed and addressing hip muscle imbalances selectively. Free-weight hip abduction exercises done in side-lying, whether the hip is extended or flexed, have been thoroughly studied for their effects on GMed and TFL activation,⁽¹⁸⁻²³⁾ with the flexed-hip variation demonstrating the lowest TFL engagement.⁽¹⁸⁾ However, few studies have explored hip abduction performance on resistance machines.⁽²⁴⁾ Certain variations of the seated hip abduction machine allow users to perform exercises at different hip flexion angles, but no studies have compared GMed and TFL activity across these angles. Hip flexion appears to decrease TFL activity,⁽¹⁸⁾ while altering GMed fiber orientation, which could shift its role toward internal rotation⁽²⁵⁾ and potentially reduce its abductor function. However, some research has shown significant activity even when the hip is flexed.⁽¹⁸⁾ To clarify this and find effective ways to maximize GMed activation while minimizing TFL engagement, this study examined electromyographic activity of GMed and TFL during seated hip abduction at various hip flexion angles. METHODS Participants This study received approval from the Research Ethics Committee of the Center for Biological and Health Sciences at the State University of Pará (approval no. 6.302.122). All procedures adhered to the ethical standards of the Declaration of Helsinki (revised in Fortaleza, Brazil, 2013) and the Brazilian National Health Council Resolutions no. 466/2012 and no. 510/2016. A total of 14 individuals volunteered for this investigation, including 11 men and 3 women who were recreationally active and had at least 6 months of resistance training experience. The sample size is consistent with previous studies.⁽²⁶⁾ The sample had a mean age of 25.1 ± 4.5 years, an average height of 1.70 ± 0.05 meters, and a mean body mass of 86.2 ± 0.08 kilograms. All participants were fully informed of the experimental procedures, exercise protocols, potential benefits, and associated risks before providing written informed consent. Participants were excluded if they had cardiovascular, neurological, or musculoskeletal conditions that could impair biomechanics during exercise. Protocol Testing took place over three separate days. Session 1 involved anthropometric measurements and familiarization, with two sets of 12 repetitions for each hip abduction variation using self-selected loads. Session 2, 48 hours later, focused on six-repetition maximum (6RM) testing. Session 3, another 48 hours afterward, included electromyographic recording. All sessions were conducted at approximately 24°C at 4:00 PM. Warm-up followed NSCA guidelines. Participants performed up to 5 attempts to determine the 6RM for each variation, with 5-minute rest periods between attempts. MVIC tests were performed in a side-lying position with the neutral pelvis and the dominant hip abducted 10°.⁽²²⁾ Participants completed two warm-up sets of 15 bodyweight squats, then exerted maximum force for 5 seconds with strong verbal encouragement. EMG signals of GMed and TFL were recorded during the MVIC. Exercise variations Three variations of the seated hip abduction exercise were performed on the abduction machine at 45°, 90°, and 135° of hip flexion (Fig. 1 ). The order was randomized for each participant to prevent sequence effects. In the 45° hip flexion condition, participants sat with their trunks slightly reclined relative to vertical. A stable step platform was placed behind the backrest to support the participant’s torso and maintain the desired 45° of hip flexion throughout the movement. The pelvis was kept in a neutral position, avoiding posterior or anterior tilting, and the spine remained aligned with the backrest. The arms rested lightly on the machine's lateral handles to aid stabilization without contributing to the movement. From this position, participants performed hip abduction by pressing the padded levers laterally until reaching their individual maximum range of motion, then returning to the starting position in a controlled manner. In the 90° hip flexion condition, participants sat upright with their trunks vertically, and their hips and knees flexed at approximately right angles. The pelvis was pressed against the backrest, and the torso stayed in contact throughout the entire exercise. The abduction movement involved moving the thighs laterally from a neutral position to the participant’s maximum comfortable abduction, then returning them to midline under control. In the 135° hip flexion condition, participants leaned forward from a seated position to reach approximately 135° hip flexion while keeping the pelvis stable and the lumbar spine in neutral alignment. This position was selected to simulate a more flexed hip posture and to alter the orientation of the gluteal and tensor fasciae latae fibers. The hands were placed on the side handles or thighs to help maintain balance, and abduction was performed through the full available range of motion without compensatory trunk movement. For all conditions, the exact hip flexion angle was verified using a pendular goniometer (Sanny Fleximeter FL6010). Participants were instructed to perform the concentric (abduction) and eccentric (adduction) phases at a steady cadence of one second per phase, guided by an audible metronome set at 60 beats per minute. Full range of motion was required in every repetition. If any deviation from the prescribed posture or movement pattern was observed—such as excessive pelvic rotation, lumbar compensation, or incomplete abduction—the trial was immediately stopped and repeated after a five-minute rest period to ensure biomechanical consistency across all test conditions. Electromyography All subjects were instructed not to perform any lower limb exercises within 24 hours before testing and to avoid consuming stimulant beverages or medications on the day of the strength and electromyography tests. Electromyographic recordings were performed using the New Miotool (Miotec Equipamentos Biomédicos Ltda, Porto Alegre, Brazil), with the digital channel ports connected to recording electrodes (TSD150B, Biopac System Inc., CA) and a ground reference electrode (Kendall 100 Series Foam Electrodes, Medtronic, MN). The electrodes were then placed following the European recommendations for Surface Electromyography for Non-Invasive Muscle Assessment (SENIAM) on a muscle region of the right side of the body. The electromyograph signal was recorded on a microcomputer with Miograph data acquisition software (Miotec). The files were processed and exported for analysis using GraphPad Prism 8.4.3 software. The signal was filtered using a 5th-order Butterworth digital filter with cutoff frequencies of 20–500 Hz. Two electrodes with a 15 mm radius (Kendall Mini Medi-Trace 100 - Tyco Healthcare, São Paulo, SP, Brazil) and a 20 mm center distance were attached to the skin over the muscle belly after carefully shaving and cleaning the area with an abrasive cleaner and alcohol swabs to reduce skin impedance, aligned with the muscle fiber orientation of each muscle, according to Leis and Trapani.⁽²⁷⁾ The myoelectric signals of the GMed and TFL muscles were evaluated following the SENIAM recommendations. RMS EMG signals were recorded throughout each exercise, and the data were normalized to maximum voluntary isometric contraction (MVIC) and expressed as %MVIC. The entire EMG signal during the MVIC of each muscle was used to calculate the RMS value. The highest RMS values obtained in the MVIC for each muscle were used to normalize the signals recorded during each exercise. The contraction rhythm times during the exercises were timed with a metronome (Korg MA-2 Black Compact Digital Metronome) set to 60 beats per minute. To help clarify the timing of each movement phase, an evaluator provided verbal instructions based on the metronome signals. Each participant completed 3 repetitions of each exercise, with 1 second allocated for the concentric phase and 1 second for the eccentric phase, using 60% of 6RM to maintain a steady cadence throughout. The electromyographic recordings of the three repetitions were analyzed to identify the peaks and RMS means, which were then normalized according to the %MVIC. Statistical analysis Data (mean ± SD) were tested for normality using the Shapiro–Wilk test. Due to non-normal distribution, Friedman’s test followed by Dunn’s post hoc analysis was performed (p < 0.05). Effect sizes (Hedges’ g, 95% CI) were categorized as trivial (< 0.2), small (0.2–0.5), moderate (0.5–0.8), or large (≥ 0.8).⁽²⁸⁾ RESULTS Regarding the electromyographic activity of the TFL, the analysis showed that performing the condition with the hip flexed at 45° resulted in significantly higher peak activation compared to the 135° condition (p = 0.0003; 95% CI = − 3.34 to − 1.20; Hedges’ g = − 2.4). However, there was no statistically significant difference between 45° and 90° (p = 0.3074; 95% CI = − 1.34 to 0.154; g = − 0.506), nor between 90° and 135° (p = 0.0742; 95% CI = − 1.74 to − 0.621; g = − 1.23). The same trend was observed for the mean TFL activation, where the 45° position induced greater muscle activity than 135° (p < 0.0001; 95% CI = − 2.79 to − 1.65; g = − 2.13), but no difference was found between 45° and 90° (p = 0.6620; 95% CI = − 1.26 to 0.294; g = − 0.386). Additionally, the 90° position showed significantly greater mean activation compared to 135° (p = 0.0066; 95% CI = − 1.77 to − 0.637; g = − 1.06). Expressed as percentage differences, these findings showed a 32.17% higher peak activation at 45° compared to 90° (p < 0.01), a 73.44% higher value at 45° compared to 135° (p < 0.0001), and a 60.84% higher value at 90° compared to 135° (p < 0.001). Regarding mean activation, the 45° position had a 35.01% higher mean than 90° (p < 0.05), a 75.84% increase compared to 135° (p < 0.0001), and the 90° condition exceeded 135° by 62.82% (p < 0.01). Overall, these data confirm a gradual decline in TFL activity with increasing hip flexion angle. For the GMed, peak electromyographic amplitude did not significantly differ between 45° and 90° (p = 0.6620; 95% CI = − 1.12 to 0.0795; g = − 0.375), but was significantly higher at 45° than at 135° (p = 0.0007; 95% CI = − 1.68 to − 0.623; g = − 1.06). Additionally, the 90° position also showed higher peak activity than the 135° position (p = 0.0429; 95% CI = − 1.32 to − 0.205; g = − 0.722). The analysis of mean activation showed a similar pattern. There was no statistically significant difference between 45° and 90° (p > 0.9999; 95% CI = − 0.715 to 0.128; g = − 0.164), while both 45° and 90° exhibited greater mean activity than 135° (p = 0.0007; 95% CI = − 1.6 to − 0.462; g = − 0.968, and p = 0.0007; 95% CI = − 1.5 to − 0.423; g = − 0.851, respectively). The descriptive analysis confirmed these statistical results, showing that only the 45° condition had significantly higher peak activity than the 135° configuration (+ 42.29%; p < 0.05), while no differences were seen between 45° and 90° or between 90° and 135°. The mean activation followed the same pattern, with the 45° variation surpassing 135° by 36.57% (p < 0.05), but no significant differences were found in the other comparisons. When examining the ratio of GMed to TFL activation (GMed:TFL), calculated by dividing the mean %MVIC of GMed by that of TFL, values greater than 1.0 indicated dominance of GMed activity. The 135° configuration produced the highest ratio (3.335 ± 2.463), which was significantly higher than the ratios observed at 45° (0.820 ± 0.277; p < 0.001) and 90° (1.326 ± 0.480; p < 0.01), with no significant difference between 45° and 90°. This result shows that, despite the lower absolute GMed activation at 135°, the relative contribution of GMed compared to TFL was notably increased in this more flexed position. DISCUSSION This study aimed to determine whether the hip flexion angle affects the electromyographic activity of the gluteus medius and tensor fasciae latae during hip abduction on a seated abduction machine. The results showed that both peak and average TFL activity gradually decreased as hip flexion increased from 45° to 135°. In contrast, GMed remained relatively stable between 45° and 90°, with a sharp decline at 135°. Notably, the GMed to TFL activity ratio increased significantly at 135°, indicating enhanced selectivity of GMed recruitment and a corresponding decrease in TFL dominance. These results show that changes in hip flexion affect both the mechanical environment and the neuromuscular recruitment strategies of the primary hip abductors. The TFL, as a biarticular muscle that acts as a hip flexor, internal rotator, and abductor, faces a mechanical disadvantage when the hip is flexed beyond 90°. In this position, its fibers are shortened, placing the muscle in a less favorable part of the length–tension curve, which decreases its ability to generate force and thus reduces its electromyographic activity. This mechanical disadvantage likely explains the observed gradual decrease in TFL activation at higher hip flexion angles in this study. Interestingly, Fujisawa et al. observed a similar trend in isometric abduction conditions.⁽²⁹⁾ In their experiment with hip flexion angles ranging from 0° to 80°, the TFL showed a progressive and significant decrease in EMG amplitude as flexion increased, confirming that the muscle’s abductor efficiency declines when the hip moves into greater flexion. The authors attributed this to a change in the TFL’s line of action, which becomes nearly perpendicular to the femoral shaft, transforming the muscle’s role from abductor to hip flexor. Therefore, both studies agree that increasing hip flexion puts the TFL in a mechanically disadvantaged position, reducing its contribution to abduction torque. In contrast, the gluteus medius has a complex, fan-shaped structure, with anterior fibers that help with hip flexion and internal rotation, and posterior fibers that assist in extension and external rotation. The middle part of the muscle remains a key abductor throughout most of the hip's range of motion. As the hip flexes, the fiber orientation of the gluteus medius changes, reducing the moment arm for pure abduction while still playing a significant role in dynamic pelvic stabilization. The relatively consistent activation across 45°–90° likely indicates a compensatory redistribution of regional fiber recruitment. Conversely, the sharp decrease at 135° suggests that at extreme flexion, its role shifts more toward internal rotation and pelvic stabilization instead of actively producing abduction torque. Supporting this interpretation, Fujisawa et al. reported that GMed activity remained statistically unchanged across flexion angles from 0° to 80°, even as abduction intensity increased.⁽²⁹⁾ This stability indicates that the GMed maintains its stabilizing role regardless of hip position, aligning with the current observation of steady activation between 45° and 90° and reduced amplitude only at extreme flexion (135°). The notable increase in the GMed:TFL ratio at 135° offers an important practical insight. Although activation of both muscles decreased at this higher flexion angle, TFL activity was suppressed more, resulting in a threefold increase in the GMed’s selective activation index. Fujisawa’s findings support this, as they also showed a rise in relative gluteal contribution during flexed-hip abduction — especially in the upper part of the gluteus maximus, which reached its peak activation at 80° of flexion.⁽²⁹⁾ Overall, these data reinforce the idea that hip flexion shifts recruitment toward the gluteal muscles while decreasing TFL involvement. This finding is directly relevant to clinical and strength-training practices, as exercises involving greater hip flexion during abduction can improve GMed recruitment while decreasing TFL overactivity. This strategy is useful in rehabilitation approaches that target frontal-plane instability, excessive femoral internal rotation, and lateral patellar tracking—conditions linked to TFL dominance and inadequate gluteus medius activation. Comparison with prior studies shows partial agreement. Brandt et al. observed increased GMed activity during side-lying abduction with elastic resistance, with the hip in a neutral position, compared to seated abduction on a machine at about 90°, indicating that external stabilization and load type significantly affect activation levels.⁽²⁴⁾ De Almeida Paz et al. reported similar GMed activation across hip flexion angles of 0°, 45°, and 90° when resistance loads were equalized, supporting the current study’s finding of comparable values between 45° and 90°.⁽²⁶⁾ However, the present results go further by showing that at 135° of hip flexion, both GMed and TFL activity decrease sharply. Despite this, GMed remains a greater contributor to total abductor effort. For TFL, the current results support McBeth et al.'s findings, who reported that hip abduction performed with the hip in a neutral position and externally rotated produces higher TFL activity and lower GMed activation than abduction without rotation.⁽¹⁹⁾ These authors suggested that rotational and flexional positions alter the relative torque contributions of these muscles by changing their lines of action. The consistent decrease in TFL activity with hip flexion observed in this study thus supports the idea that increasing hip flexion mechanically shortens the TFL and limits its torque potential. It is worth noting that apparent discrepancies between descriptive percentage differences and inferential statistical results likely arise from methodological and analytical nuances. While the descriptive data show raw proportional changes in EMG amplitude across conditions, the inferential results are obtained from nonparametric within-subject rank-based tests adjusted for multiple comparisons. As a result, minor differences may seem statistically nonsignificant despite notable percentage changes, especially given the relatively small sample size. Nonetheless, the overall trend of change remained consistent across all analyses, supporting the robustness of the main findings. From a practical perspective, these results suggest that performing hip abduction with moderate hip flexion (around 45°–90°) may be optimal for maximizing overall gluteus medius activation. Conversely, greater hip flexion (about 135°) can be strategically used to selectively activate GMed over TFL, such as in corrective exercise or rehabilitation settings. The findings emphasize the importance of adjusting exercise setup not only to control overall load but also to influence relative muscle recruitment patterns and improve force distribution around the hip and pelvis. The current study has some limitations. First, although participants were carefully instructed to maintain specific hip flexion angles during each condition, they still had difficulty keeping these angles consistent throughout the entire set of repetitions. Even small deviations in joint positioning can change muscle length–tension relationships and moment arms, which in turn can affect electromyographic output. Second, the investigation focused only on the tensor fasciae latae and gluteus medius, excluding other muscles that work together, such as the gluteus maximus, which also contributes to hip abduction, mainly through its upper fibers. Because the gluteus maximus undergoes significant changes in fiber orientation and moment arms during different hip positions, including this muscle in future studies could provide a more complete understanding of overall abductor mechanics. Third, the maximum hip abduction amplitude for each participant was not measured, which limits the ability to determine if variability in the range of motion affected muscle activation. Additionally, due to technical issues during recording, the repetitions were analyzed as complete movement cycles instead of being separated into concentric and eccentric phases, potentially hiding phase-specific differences in neuromuscular strategy. Fourth, small discrepancies between descriptive and inferential statistics, especially in comparisons at 90° and 135°, reflect the natural variability of nonparametric testing with limited samples. While these differences do not alter the overall interpretation, they emphasize the need for larger, more consistent samples in future studies to confirm these trends with more robust statistical support. Fifth, the study sample consisted exclusively of healthy, resistance-trained young adults. Therefore, the results cannot be generalized to populations with musculoskeletal disorders, sedentary individuals, or older adults. Further research examining sex-related and pathological differences would help clarify the clinical relevance of these findings. Finally, the results are specific to the mechanical setup of the abduction machine used in this study. Variations in seat tilt, pad height, backrest design, or stabilization systems on other machines could change external torque directions and influence the muscle recruitment patterns observed here. Despite these limitations, the study provides valuable insights into how different hip positions affect the neuromuscular balance between the gluteus medius and tensor fasciae latae during resistance exercise, offering a scientific foundation for more accurate hip abduction training guidelines in both clinical and performance environments. CONCLUSIONS The current study showed that hip abduction at 45° of hip flexion resulted in greater activation of both GMed and TFL compared to 135°, with 90° producing intermediate levels. However, the 135° flexion condition led to the highest GMed:TFL ratio, indicating better GMed selectivity and less TFL involvement. These findings highlight the importance of hip joint position in exercise planning and suggest that performing hip abduction with increased hip flexion may more effectively target the GMed, providing a practical approach for strengthening and rehabilitating the pelvic abductors while reducing TFL dominance. Declarations Author Contributions: All authors contributed equally to the conception, design, data collection, analysis, and interpretation of the study. Dr. Walter Krause Neto supervised the entire research process and prepared the final version of the manuscript. All authors reviewed, edited, and approved the final submission. Ethical Approval: The study was approved by the Research Ethics Committee of the State University of Pará (approval no. 6.302.122) and conducted according to the Declaration of Helsinki (Fortaleza revision, 2013). ACKNOWLEDGEMENTS We want to thank the volunteers who helped us during the collections. References Neumann DA. Kinesiology of the hip: a focus on muscular actions. J Orthop Sports Phys Ther . 2010;40(2):82–94. doi: 10.2519/jospt.2010.3025 Powers CM. The influence of abnormal hip mechanics on knee injury: a biomechanical perspective. J Orthop Sports Phys Ther. 2010;40(2):42–51. Strauss EJ, Nho SJ, Kelly BT. Greater trochanteric pain syndrome. Sports Med Arthrosc Rev. 2010;18(2):113–119. Nakagawa TH, Moriya ET, Maciel CD, Serrão FV. Trunk, pelvis, hip, and knee kinematics, hip strength, and gluteal muscle activation during a single-leg squat in males and females with and without patellofemoral pain syndrome. J Orthop Sports Phys Ther . 2012;42(6):491–501. Buckthorpe M, Stride M, Della Villa F. Assessing and treating gluteus maximus weakness: a clinical commentary. Int J Sports Phys Ther. 2019;14(4):655–669. French HP, Dunleavy M, Cusack T. Predictors of functional capacity in older adults with osteoarthritis of the hip. Phys Ther. 2010;90(9):1251–1262. Hinman RS, Hunt MA, Creaby MW, Wrigley TV, McManus FJ, Bennell KL. Hip muscle weakness in individuals with knee osteoarthritis. Arthritis Care Res (Hoboken) . 2010;62(8):1190–1198. Fredericson M, Cookingham CL, Chaudhari AM, Dowdell BC, Oestreicher N, Sahrmann SA. Hip abductor weakness in distance runners with iliotibial band syndrome. Clin J Sport Med. 2000;10(3):169–175. Lee SP, Souza RB, Powers CM. The influence of hip abductor muscle performance on dynamic postural stability in females with patellofemoral pain. Gait Posture. 2012;36(3):425–429. doi: 10.1016/j.gaitpost.2012.03.014 Calais-Germain B. Anatomy of Movement . Seattle, WA: Eastland Press; 1993. Sahrmann SA. Diagnosis and Treatment of Movement Impairment Syndromes . St. Louis, MO: Mosby; 2001. Merican AM, Amis AA. Iliotibial band tension affects patellofemoral and tibiofemoral kinematics. J Biomech. 2009;42(10):1539–1546. doi: 10.1016/j.jbiomech.2009.03.041 Besomi M, Maclachlan L, Mellor R, Vicenzino B, Hodges PW. Tensor fascia latae muscle structure and activation in individuals with lower limb musculoskeletal conditions: a systematic review and meta-analysis. Sports Med. 2020;50:1–21. doi: 10.1007/s40279-019-01251-1 Selkowitz DM, Beneck GJ, Powers CM. Which exercises target the gluteal muscles while minimizing activation of the tensor fascia lata? Electromyographic assessment using fine-wire electrodes. J Orthop Sports Phys Ther . 2013;43(2):54–64. doi: 10.2519/jospt.2013.4116 Sidorkewicz N, Cambridge ED, McGill SM. Examining the effects of altering hip orientation on gluteus medius and tensor fascia latae interplay during common non-weight-bearing hip rehabilitation exercises. Clin Biomech (Bristol, Avon) . 2014;29(9):971–976. doi: 10.1016/j.clinbiomech.2014.09.002 Bishop BN, Greenstein J, Etnoyer-Slaski JL, Hornsby E, Conrad K, Ingersoll CD. Electromyographic analysis of gluteus maximus, gluteus medius, and tensor fascia latae during therapeutic exercises with and without elastic resistance. Int J Sports Phys Ther . 2018;13(4):668–675. Willcox EL, Burden AM. The influence of varying hip angle and pelvis position on muscle recruitment patterns of the hip abductor muscles during the clam exercise. J Orthop Sports Phys Ther . 2013;43(5):325–331. doi: 10.2519/jospt.2013.4004 Chan MK, Chow KW, Lai AY, Mak NK, Sze JC, Tsang SM. The effects of therapeutic hip exercise with abdominal core activation on recruitment of the hip muscles. BMC Musculoskelet Disord. 2017;18(1):313. doi: 10.1186/s12891-017-1674-2 McBeth JM, Earl-Boehm JE, Cobb SC, Huddleston WE. Hip muscle activity during three side-lying hip-strengthening exercises in distance runners. J Athl Train. 2012;47(1):15–23. doi: 10.4085/1062-6050-47.1.15 Tsang SMH, Lam AHM, Ng MHL, Ng KWK, Tsui COH, Yiu B. Abdominal muscle recruitment and its effect on the activity level of the hip and posterior thigh muscles during therapeutic exercises of the hip joint. J Electromyogr Kinesiol. 2018;42:10–19. doi: 10.1016/j.jelekin.2018.06.005 Caon G, Silva T, Pereira L, et al. Exercícios terapêuticos mais eficientes na ativação de glúteo máximo e glúteo médio: revisão de literatura. Saúde Desenvol Hum. 2020;8(2):139–150. Frigotto MF, Cardoso CA, Santos RR, Rodrigues R. Gluteus medius and tensor fascia latae muscle activation levels during multi-joint strengthening exercises. Motriz Rev Educ Fis. 2019;25:e0030011. doi: 10.1590/s1980-6574201900030011 Brandt M, Jakobsen MD, Thorborg K, Sundstrup E, Jay K, Andersen LL. Perceived loading and muscle activity during hip strengthening exercises: comparison of elastic resistance and machine exercises. Int J Sports Phys Ther . 2013;8(6):811–819. PMID:24377067; PMCID:PMC3867074 Delp SL, Hess WE, Hungerford DS, Jones LC. Variation of rotation moment arms with hip flexion. J Biomech. 1999;32(5):493–501. doi: 10.1016/S0021-9290(99)00032-9 de Almeida Paz I, Frigotto MF, Cardoso CA, Rabello R, Rodrigues R. Hip abduction machine is better than free weights to target the gluteus medius while minimizing tensor fascia latae activation. J Bodyw Mov Ther. 2022;30:160–167. doi: 10.1016/j.jbmt.2022.01.001 Leis AA, Trapani VC. Atlas of Nerve Conduction Studies and Electromyography . 3rd ed. New York, NY: Oxford University Press; 2013. Ho J, Tumkaya T, Aryal S, Choi H, Claridge-Chang A. Moving beyond P values: data analysis with estimation graphics. Nat Methods. 2019;16(7):565–566. doi: 10.1038/s41592-019-0470-3 Fujisawa H, Suzuki H, Yamaguchi E, Yoshiki H, Wada Y, Watanabe A. Hip muscle activity during isometric contraction of hip abduction. J Phys Ther Sci. 2014;26(2):187–190. doi: 10.1589/jpts.26.187 Additional Declarations No competing interests reported. Cite Share Download PDF Status: Posted Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-8523653","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":569727303,"identity":"ad2a3e60-76d0-44fa-9337-2cfea41d35bd","order_by":0,"name":"Alexandre Maia Farias","email":"","orcid":"","institution":"Pará State University","correspondingAuthor":false,"prefix":"","firstName":"Alexandre","middleName":"Maia","lastName":"Farias","suffix":""},{"id":569727306,"identity":"bb1418ef-419c-4153-ab83-8ff07bf8446e","order_by":1,"name":"Leon Claudio Pinheiro Leal","email":"","orcid":"","institution":"Pará State 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13:33:24","extension":"html","order_by":12,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":91208,"visible":true,"origin":"","legend":"","description":"","filename":"earlyproof.html","url":"https://assets-eu.researchsquare.com/files/rs-8523653/v1/72de653859cf6c7cd5c0b97b.html"},{"id":99792728,"identity":"44dcb64a-9b2d-4609-9aee-a0e440f4513c","added_by":"auto","created_at":"2026-01-08 13:25:26","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":298397,"visible":true,"origin":"","legend":"\u003cp\u003eThree variations of the seated hip abduction exercise were performed on the abduction machine at 45° (A), 90° (B), and 135° (C) of hip flexion.\u003c/p\u003e","description":"","filename":"floatimage1.png","url":"https://assets-eu.researchsquare.com/files/rs-8523653/v1/017a009c3979898b9c916ae3.png"},{"id":99792281,"identity":"841f75d0-2f9e-445f-809f-d0d193651d71","added_by":"auto","created_at":"2026-01-08 13:17:23","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":82439,"visible":true,"origin":"","legend":"\u003cp\u003eElectrode positioning. The circular points indicate the anatomical locations specified by the SENIAM guidelines for proper electrode placement in X.\u003c/p\u003e","description":"","filename":"floatimage2.png","url":"https://assets-eu.researchsquare.com/files/rs-8523653/v1/738436f1600f5fe86da38e04.png"},{"id":99794108,"identity":"1afacef8-08f3-4853-aa80-6918b2b59ed4","added_by":"auto","created_at":"2026-01-08 13:33:58","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":166590,"visible":true,"origin":"","legend":"\u003cp\u003ePeak activation related to %MVIC of TFL. B: average activation related to %MVIC of TFL. %MVIC: percentage of maximum voluntary isometric contraction; TFL: tensor fascia lata. C: Peak activation related to %MVIC of TFL. B: average activation related to %MVIC of TFL. %MVIC: percentage of maximum voluntary isometric contraction; TFL: tensor fascia lata. (*) = p ≤ 0.05; (**) = p ≤ 0.01; (***) = p ≤ 0.0001.\u003c/p\u003e","description":"","filename":"floatimage3.png","url":"https://assets-eu.researchsquare.com/files/rs-8523653/v1/82c5f16d7d4603c35f2443df.png"},{"id":99600729,"identity":"592e8a36-2e2a-4f59-96a8-a8c85a4b2d49","added_by":"auto","created_at":"2026-01-06 10:34:26","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":39970,"visible":true,"origin":"","legend":"\u003cp\u003eGmed: TFL ratio. The mean activation rate of Gmed is divided by the mean activation of TFL (GMed:TFL). (**) = p\u0026lt;0.01; (***) = p\u0026lt;0.001.\u003c/p\u003e","description":"","filename":"floatimage4.png","url":"https://assets-eu.researchsquare.com/files/rs-8523653/v1/7a592c1edc8532c52db2fc4f.png"},{"id":106401826,"identity":"d589556a-256a-4f1c-b342-98b467d03e21","added_by":"auto","created_at":"2026-04-08 09:09:54","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":981007,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-8523653/v1/8ca53771-dffc-4509-a995-2ea705194a87.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Not All Hip Abductions Are Equal: The 45° Paradox Between Gluteus Medius and Tensor Fasciae Latae","fulltext":[{"header":"INTRODUCTION","content":"\u003cp\u003eSkill and proficiency in performing sports, occupational, and functional activities rely on the coordinated action of agonist and antagonist muscles, as well as those that stabilize the musculoskeletal system. This coordination ensures efficient movement and helps prevent injuries caused by joint instability. Neuromuscular control of the lower-limb muscles is essential for daily activities like walking, sitting, and standing, as well as for athletic tasks such as jumping and running.⁽\u0026sup1;⁾\u003c/p\u003e \u003cp\u003eIntrinsic deficits in motor control of the lower-limb girdle can cause abnormal force distribution at the hip, affecting both the lower and upper kinetic chains and potentially leading to biomechanical and clinical problems over time.⁽\u0026sup1;⁾ Weakness in the hip muscles, especially the hip abductors and external rotators, has been identified as a key factor in developing pelvic and lower-limb pathologies.⁽\u0026sup2;⁻⁴⁾\u003c/p\u003e \u003cp\u003eThe gluteus medius (GMed) is a crucial stabilizer of the pelvis and a controller of femoral movement during single-leg tasks.⁽⁵⁾ This pelvic control is vital for limiting hip adduction during gait.⁽⁶,\u0026sup1;⁾ Anatomically, the GMed comprises anterior, middle, and posterior fiber groups, all of which aid in hip abduction. However, based on their anatomical position, the anterior fibers assist with hip flexion and internal rotation, while the posterior fibers support hip extension and external rotation.⁽\u0026sup1;⁾\u003c/p\u003e \u003cp\u003eDuring single-leg stance, weakness in the GMed can increase compressive and shear forces on the patellofemoral joint due to greater hip adduction.⁽\u0026sup2;⁾ This increase appears to be a risk factor for patellofemoral pain,⁽\u0026sup2;⁻⁴⁾ knee osteoarthritis,⁽⁷⁾ anterior cruciate ligament injury,⁽\u0026sup2;⁾ and iliotibial band syndrome.⁽⁸,⁹⁾\u003c/p\u003e \u003cp\u003eAnother key muscle in lower-limb movement is the tensor fasciae latae (TFL), which, in addition to aiding in hip abduction, also supports hip flexion and internal rotation.⁽\u0026sup1;⁰,\u0026sup1;\u0026sup1;⁾ Sahrmann⁽\u0026sup1;\u0026sup2;⁾ proposed that a dominance of TFL force over GMed during hip abduction might cause excessive internal rotation during single-limb support tasks. Weaknesses in GMed may result in increased TFL activation and overactivity.⁽⁸,\u0026sup2;⁾ This imbalance could contribute to lower limb orthopedic issues, including patellar lateralization caused by excess tension transmitted from the TFL through the iliotibial tract to the knee's lateral retinacula.⁽\u0026sup1;\u0026sup3;,\u0026sup1;,\u0026sup1;⁴⁾\u003c/p\u003e \u003cp\u003eUsing strength exercises that promote greater GMed activation relative to TFL\u0026mdash;measured by the GMed:TFL ratio⁽\u0026sup1;⁵⁻\u0026sup1;⁷⁾\u0026mdash;is a common resistance training method for strengthening the GMed and addressing hip muscle imbalances selectively. Free-weight hip abduction exercises done in side-lying, whether the hip is extended or flexed, have been thoroughly studied for their effects on GMed and TFL activation,⁽\u0026sup1;⁸⁻\u0026sup2;\u0026sup3;⁾ with the flexed-hip variation demonstrating the lowest TFL engagement.⁽\u0026sup1;⁸⁾ However, few studies have explored hip abduction performance on resistance machines.⁽\u0026sup2;⁴⁾\u003c/p\u003e \u003cp\u003eCertain variations of the seated hip abduction machine allow users to perform exercises at different hip flexion angles, but no studies have compared GMed and TFL activity across these angles. Hip flexion appears to decrease TFL activity,⁽\u0026sup1;⁸⁾ while altering GMed fiber orientation, which could shift its role toward internal rotation⁽\u0026sup2;⁵⁾ and potentially reduce its abductor function. However, some research has shown significant activity even when the hip is flexed.⁽\u0026sup1;⁸⁾ To clarify this and find effective ways to maximize GMed activation while minimizing TFL engagement, this study examined electromyographic activity of GMed and TFL during seated hip abduction at various hip flexion angles.\u003c/p\u003e"},{"header":"METHODS","content":"\u003cp\u003e \u003cb\u003eParticipants\u003c/b\u003e \u003c/p\u003e \u003cp\u003e This study received approval from the Research Ethics Committee of the Center for Biological and Health Sciences at the State University of Par\u0026aacute; (approval no. 6.302.122). All procedures adhered to the ethical standards of the Declaration of Helsinki (revised in Fortaleza, Brazil, 2013) and the Brazilian National Health Council Resolutions no. 466/2012 and no. 510/2016.\u003c/p\u003e \u003cp\u003eA total of 14 individuals volunteered for this investigation, including 11 men and 3 women who were recreationally active and had at least 6 months of resistance training experience. The sample size is consistent with previous studies.⁽\u0026sup2;⁶⁾ The sample had a mean age of 25.1\u0026thinsp;\u0026plusmn;\u0026thinsp;4.5 years, an average height of 1.70\u0026thinsp;\u0026plusmn;\u0026thinsp;0.05 meters, and a mean body mass of 86.2\u0026thinsp;\u0026plusmn;\u0026thinsp;0.08 kilograms. All participants were fully informed of the experimental procedures, exercise protocols, potential benefits, and associated risks before providing written informed consent.\u003c/p\u003e \u003cp\u003eParticipants were excluded if they had cardiovascular, neurological, or musculoskeletal conditions that could impair biomechanics during exercise.\u003c/p\u003e \u003cp\u003e \u003cb\u003eProtocol\u003c/b\u003e \u003c/p\u003e \u003cp\u003eTesting took place over three separate days. Session 1 involved anthropometric measurements and familiarization, with two sets of 12 repetitions for each hip abduction variation using self-selected loads. Session 2, 48 hours later, focused on six-repetition maximum (6RM) testing. Session 3, another 48 hours afterward, included electromyographic recording. All sessions were conducted at approximately 24\u0026deg;C at 4:00 PM.\u003c/p\u003e \u003cp\u003e Warm-up followed NSCA guidelines. Participants performed up to 5 attempts to determine the 6RM for each variation, with 5-minute rest periods between attempts. MVIC tests were performed in a side-lying position with the neutral pelvis and the dominant hip abducted 10\u0026deg;.⁽\u0026sup2;\u0026sup2;⁾ Participants completed two warm-up sets of 15 bodyweight squats, then exerted maximum force for 5 seconds with strong verbal encouragement. EMG signals of GMed and TFL were recorded during the MVIC.\u003c/p\u003e \u003cp\u003e \u003cb\u003eExercise variations\u003c/b\u003e \u003c/p\u003e \u003cp\u003eThree variations of the seated hip abduction exercise were performed on the abduction machine at 45\u0026deg;, 90\u0026deg;, and 135\u0026deg; of hip flexion (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). The order was randomized for each participant to prevent sequence effects.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eIn the \u003cb\u003e45\u0026deg;\u003c/b\u003e hip flexion condition, participants sat with their trunks slightly reclined relative to vertical. A stable step platform was placed behind the backrest to support the participant\u0026rsquo;s torso and maintain the desired 45\u0026deg; of hip flexion throughout the movement. The pelvis was kept in a neutral position, avoiding posterior or anterior tilting, and the spine remained aligned with the backrest. The arms rested lightly on the machine's lateral handles to aid stabilization without contributing to the movement. From this position, participants performed hip abduction by pressing the padded levers laterally until reaching their individual maximum range of motion, then returning to the starting position in a controlled manner.\u003c/p\u003e \u003cp\u003eIn the \u003cb\u003e90\u0026deg;\u003c/b\u003e hip flexion condition, participants sat upright with their trunks vertically, and their hips and knees flexed at approximately right angles. The pelvis was pressed against the backrest, and the torso stayed in contact throughout the entire exercise. The abduction movement involved moving the thighs laterally from a neutral position to the participant\u0026rsquo;s maximum comfortable abduction, then returning them to midline under control.\u003c/p\u003e \u003cp\u003eIn the \u003cb\u003e135\u0026deg;\u003c/b\u003e hip flexion condition, participants leaned forward from a seated position to reach approximately 135\u0026deg; hip flexion while keeping the pelvis stable and the lumbar spine in neutral alignment. This position was selected to simulate a more flexed hip posture and to alter the orientation of the gluteal and tensor fasciae latae fibers. The hands were placed on the side handles or thighs to help maintain balance, and abduction was performed through the full available range of motion without compensatory trunk movement.\u003c/p\u003e \u003cp\u003eFor all conditions, the exact hip flexion angle was verified using a pendular goniometer (Sanny Fleximeter FL6010). Participants were instructed to perform the concentric (abduction) and eccentric (adduction) phases at a steady cadence of one second per phase, guided by an audible metronome set at 60 beats per minute. Full range of motion was required in every repetition. If any deviation from the prescribed posture or movement pattern was observed\u0026mdash;such as excessive pelvic rotation, lumbar compensation, or incomplete abduction\u0026mdash;the trial was immediately stopped and repeated after a five-minute rest period to ensure biomechanical consistency across all test conditions.\u003c/p\u003e \u003cp\u003e \u003cb\u003eElectromyography\u003c/b\u003e \u003c/p\u003e \u003cp\u003eAll subjects were instructed not to perform any lower limb exercises within 24 hours before testing and to avoid consuming stimulant beverages or medications on the day of the strength and electromyography tests.\u003c/p\u003e \u003cp\u003eElectromyographic recordings were performed using the New Miotool (Miotec Equipamentos Biom\u0026eacute;dicos Ltda, Porto Alegre, Brazil), with the digital channel ports connected to recording electrodes (TSD150B, Biopac System Inc., CA) and a ground reference electrode (Kendall 100 Series Foam Electrodes, Medtronic, MN). The electrodes were then placed following the European recommendations for Surface Electromyography for Non-Invasive Muscle Assessment (SENIAM) on a muscle region of the right side of the body. The electromyograph signal was recorded on a microcomputer with Miograph data acquisition software (Miotec). The files were processed and exported for analysis using GraphPad Prism 8.4.3 software. The signal was filtered using a 5th-order Butterworth digital filter with cutoff frequencies of 20\u0026ndash;500 Hz. Two electrodes with a 15 mm radius (Kendall Mini Medi-Trace 100 - Tyco Healthcare, S\u0026atilde;o Paulo, SP, Brazil) and a 20 mm center distance were attached to the skin over the muscle belly after carefully shaving and cleaning the area with an abrasive cleaner and alcohol swabs to reduce skin impedance, aligned with the muscle fiber orientation of each muscle, according to Leis and Trapani.⁽\u0026sup2;⁷⁾\u003c/p\u003e \u003cp\u003eThe myoelectric signals of the GMed and TFL muscles were evaluated following the SENIAM recommendations. RMS EMG signals were recorded throughout each exercise, and the data were normalized to maximum voluntary isometric contraction (MVIC) and expressed as %MVIC. The entire EMG signal during the MVIC of each muscle was used to calculate the RMS value. The highest RMS values obtained in the MVIC for each muscle were used to normalize the signals recorded during each exercise.\u003c/p\u003e \u003cp\u003eThe contraction rhythm times during the exercises were timed with a metronome (Korg MA-2 Black Compact Digital Metronome) set to 60 beats per minute. To help clarify the timing of each movement phase, an evaluator provided verbal instructions based on the metronome signals. Each participant completed 3 repetitions of each exercise, with 1 second allocated for the concentric phase and 1 second for the eccentric phase, using 60% of 6RM to maintain a steady cadence throughout. The electromyographic recordings of the three repetitions were analyzed to identify the peaks and RMS means, which were then normalized according to the %MVIC.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003cb\u003eStatistical analysis\u003c/b\u003e \u003c/p\u003e \u003cp\u003eData (mean\u0026thinsp;\u0026plusmn;\u0026thinsp;SD) were tested for normality using the Shapiro\u0026ndash;Wilk test. Due to non-normal distribution, Friedman\u0026rsquo;s test followed by Dunn\u0026rsquo;s post hoc analysis was performed (p\u0026thinsp;\u0026lt;\u0026thinsp;0.05). Effect sizes (Hedges\u0026rsquo; g, 95% CI) were categorized as trivial (\u0026lt;\u0026thinsp;0.2), small (0.2\u0026ndash;0.5), moderate (0.5\u0026ndash;0.8), or large (\u0026ge;\u0026thinsp;0.8).⁽\u0026sup2;⁸⁾\u003c/p\u003e"},{"header":"RESULTS","content":"\u003cp\u003eRegarding the electromyographic activity of the TFL, the analysis showed that performing the condition with the hip flexed at 45\u0026deg; resulted in significantly higher peak activation compared to the 135\u0026deg; condition (p\u0026thinsp;=\u0026thinsp;0.0003; 95% CI\u0026thinsp;=\u0026thinsp;\u0026minus;\u0026thinsp;3.34 to \u0026minus;\u0026thinsp;1.20; Hedges\u0026rsquo; g\u0026thinsp;=\u0026thinsp;\u0026minus;\u0026thinsp;2.4). However, there was no statistically significant difference between 45\u0026deg; and 90\u0026deg; (p\u0026thinsp;=\u0026thinsp;0.3074; 95% CI\u0026thinsp;=\u0026thinsp;\u0026minus;\u0026thinsp;1.34 to 0.154; g\u0026thinsp;=\u0026thinsp;\u0026minus;\u0026thinsp;0.506), nor between 90\u0026deg; and 135\u0026deg; (p\u0026thinsp;=\u0026thinsp;0.0742; 95% CI\u0026thinsp;=\u0026thinsp;\u0026minus;\u0026thinsp;1.74 to \u0026minus;\u0026thinsp;0.621; g\u0026thinsp;=\u0026thinsp;\u0026minus;\u0026thinsp;1.23). The same trend was observed for the mean TFL activation, where the 45\u0026deg; position induced greater muscle activity than 135\u0026deg; (p\u0026thinsp;\u0026lt;\u0026thinsp;0.0001; 95% CI\u0026thinsp;=\u0026thinsp;\u0026minus;\u0026thinsp;2.79 to \u0026minus;\u0026thinsp;1.65; g\u0026thinsp;=\u0026thinsp;\u0026minus;\u0026thinsp;2.13), but no difference was found between 45\u0026deg; and 90\u0026deg; (p\u0026thinsp;=\u0026thinsp;0.6620; 95% CI\u0026thinsp;=\u0026thinsp;\u0026minus;\u0026thinsp;1.26 to 0.294; g\u0026thinsp;=\u0026thinsp;\u0026minus;\u0026thinsp;0.386). Additionally, the 90\u0026deg; position showed significantly greater mean activation compared to 135\u0026deg; (p\u0026thinsp;=\u0026thinsp;0.0066; 95% CI\u0026thinsp;=\u0026thinsp;\u0026minus;\u0026thinsp;1.77 to \u0026minus;\u0026thinsp;0.637; g\u0026thinsp;=\u0026thinsp;\u0026minus;\u0026thinsp;1.06).\u003c/p\u003e \u003cp\u003eExpressed as percentage differences, these findings showed a 32.17% higher peak activation at 45\u0026deg; compared to 90\u0026deg; (p\u0026thinsp;\u0026lt;\u0026thinsp;0.01), a 73.44% higher value at 45\u0026deg; compared to 135\u0026deg; (p\u0026thinsp;\u0026lt;\u0026thinsp;0.0001), and a 60.84% higher value at 90\u0026deg; compared to 135\u0026deg; (p\u0026thinsp;\u0026lt;\u0026thinsp;0.001). Regarding mean activation, the 45\u0026deg; position had a 35.01% higher mean than 90\u0026deg; (p\u0026thinsp;\u0026lt;\u0026thinsp;0.05), a 75.84% increase compared to 135\u0026deg; (p\u0026thinsp;\u0026lt;\u0026thinsp;0.0001), and the 90\u0026deg; condition exceeded 135\u0026deg; by 62.82% (p\u0026thinsp;\u0026lt;\u0026thinsp;0.01). Overall, these data confirm a gradual decline in TFL activity with increasing hip flexion angle.\u003c/p\u003e \u003cp\u003eFor the GMed, peak electromyographic amplitude did not significantly differ between 45\u0026deg; and 90\u0026deg; (p\u0026thinsp;=\u0026thinsp;0.6620; 95% CI\u0026thinsp;=\u0026thinsp;\u0026minus;\u0026thinsp;1.12 to 0.0795; g\u0026thinsp;=\u0026thinsp;\u0026minus;\u0026thinsp;0.375), but was significantly higher at 45\u0026deg; than at 135\u0026deg; (p\u0026thinsp;=\u0026thinsp;0.0007; 95% CI\u0026thinsp;=\u0026thinsp;\u0026minus;\u0026thinsp;1.68 to \u0026minus;\u0026thinsp;0.623; g\u0026thinsp;=\u0026thinsp;\u0026minus;\u0026thinsp;1.06). Additionally, the 90\u0026deg; position also showed higher peak activity than the 135\u0026deg; position (p\u0026thinsp;=\u0026thinsp;0.0429; 95% CI\u0026thinsp;=\u0026thinsp;\u0026minus;\u0026thinsp;1.32 to \u0026minus;\u0026thinsp;0.205; g\u0026thinsp;=\u0026thinsp;\u0026minus;\u0026thinsp;0.722). The analysis of mean activation showed a similar pattern. There was no statistically significant difference between 45\u0026deg; and 90\u0026deg; (p\u0026thinsp;\u0026gt;\u0026thinsp;0.9999; 95% CI\u0026thinsp;=\u0026thinsp;\u0026minus;\u0026thinsp;0.715 to 0.128; g\u0026thinsp;=\u0026thinsp;\u0026minus;\u0026thinsp;0.164), while both 45\u0026deg; and 90\u0026deg; exhibited greater mean activity than 135\u0026deg; (p\u0026thinsp;=\u0026thinsp;0.0007; 95% CI\u0026thinsp;=\u0026thinsp;\u0026minus;\u0026thinsp;1.6 to \u0026minus;\u0026thinsp;0.462; g\u0026thinsp;=\u0026thinsp;\u0026minus;\u0026thinsp;0.968, and p\u0026thinsp;=\u0026thinsp;0.0007; 95% CI\u0026thinsp;=\u0026thinsp;\u0026minus;\u0026thinsp;1.5 to \u0026minus;\u0026thinsp;0.423; g\u0026thinsp;=\u0026thinsp;\u0026minus;\u0026thinsp;0.851, respectively).\u003c/p\u003e \u003cp\u003eThe descriptive analysis confirmed these statistical results, showing that only the 45\u0026deg; condition had significantly higher peak activity than the 135\u0026deg; configuration (+\u0026thinsp;42.29%; p\u0026thinsp;\u0026lt;\u0026thinsp;0.05), while no differences were seen between 45\u0026deg; and 90\u0026deg; or between 90\u0026deg; and 135\u0026deg;. The mean activation followed the same pattern, with the 45\u0026deg; variation surpassing 135\u0026deg; by 36.57% (p\u0026thinsp;\u0026lt;\u0026thinsp;0.05), but no significant differences were found in the other comparisons.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eWhen examining the ratio of GMed to TFL activation (GMed:TFL), calculated by dividing the mean %MVIC of GMed by that of TFL, values greater than 1.0 indicated dominance of GMed activity. The 135\u0026deg; configuration produced the highest ratio (3.335\u0026thinsp;\u0026plusmn;\u0026thinsp;2.463), which was significantly higher than the ratios observed at 45\u0026deg; (0.820\u0026thinsp;\u0026plusmn;\u0026thinsp;0.277; p\u0026thinsp;\u0026lt;\u0026thinsp;0.001) and 90\u0026deg; (1.326\u0026thinsp;\u0026plusmn;\u0026thinsp;0.480; p\u0026thinsp;\u0026lt;\u0026thinsp;0.01), with no significant difference between 45\u0026deg; and 90\u0026deg;. This result shows that, despite the lower absolute GMed activation at 135\u0026deg;, the relative contribution of GMed compared to TFL was notably increased in this more flexed position.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e"},{"header":"DISCUSSION","content":"\u003cp\u003eThis study aimed to determine whether the hip flexion angle affects the electromyographic activity of the gluteus medius and tensor fasciae latae during hip abduction on a seated abduction machine. The results showed that both peak and average TFL activity gradually decreased as hip flexion increased from 45\u0026deg; to 135\u0026deg;. In contrast, GMed remained relatively stable between 45\u0026deg; and 90\u0026deg;, with a sharp decline at 135\u0026deg;. Notably, the GMed to TFL activity ratio increased significantly at 135\u0026deg;, indicating enhanced selectivity of GMed recruitment and a corresponding decrease in TFL dominance.\u003c/p\u003e \u003cp\u003eThese results show that changes in hip flexion affect both the mechanical environment and the neuromuscular recruitment strategies of the primary hip abductors. The TFL, as a biarticular muscle that acts as a hip flexor, internal rotator, and abductor, faces a mechanical disadvantage when the hip is flexed beyond 90\u0026deg;. In this position, its fibers are shortened, placing the muscle in a less favorable part of the length\u0026ndash;tension curve, which decreases its ability to generate force and thus reduces its electromyographic activity. This mechanical disadvantage likely explains the observed gradual decrease in TFL activation at higher hip flexion angles in this study.\u003c/p\u003e \u003cp\u003eInterestingly, Fujisawa et al. observed a similar trend in isometric abduction conditions.⁽\u0026sup2;⁹⁾ In their experiment with hip flexion angles ranging from 0\u0026deg; to 80\u0026deg;, the TFL showed a progressive and significant decrease in EMG amplitude as flexion increased, confirming that the muscle\u0026rsquo;s abductor efficiency declines when the hip moves into greater flexion. The authors attributed this to a change in the TFL\u0026rsquo;s line of action, which becomes nearly perpendicular to the femoral shaft, transforming the muscle\u0026rsquo;s role from abductor to hip flexor. Therefore, both studies agree that increasing hip flexion puts the TFL in a mechanically disadvantaged position, reducing its contribution to abduction torque.\u003c/p\u003e \u003cp\u003eIn contrast, the gluteus medius has a complex, fan-shaped structure, with anterior fibers that help with hip flexion and internal rotation, and posterior fibers that assist in extension and external rotation. The middle part of the muscle remains a key abductor throughout most of the hip's range of motion. As the hip flexes, the fiber orientation of the gluteus medius changes, reducing the moment arm for pure abduction while still playing a significant role in dynamic pelvic stabilization. The relatively consistent activation across 45\u0026deg;\u0026ndash;90\u0026deg; likely indicates a compensatory redistribution of regional fiber recruitment. Conversely, the sharp decrease at 135\u0026deg; suggests that at extreme flexion, its role shifts more toward internal rotation and pelvic stabilization instead of actively producing abduction torque.\u003c/p\u003e \u003cp\u003eSupporting this interpretation, Fujisawa et al. reported that GMed activity remained statistically unchanged across flexion angles from 0\u0026deg; to 80\u0026deg;, even as abduction intensity increased.⁽\u0026sup2;⁹⁾ This stability indicates that the GMed maintains its stabilizing role regardless of hip position, aligning with the current observation of steady activation between 45\u0026deg; and 90\u0026deg; and reduced amplitude only at extreme flexion (135\u0026deg;).\u003c/p\u003e \u003cp\u003eThe notable increase in the GMed:TFL ratio at 135\u0026deg; offers an important practical insight. Although activation of both muscles decreased at this higher flexion angle, TFL activity was suppressed more, resulting in a threefold increase in the GMed\u0026rsquo;s selective activation index. Fujisawa\u0026rsquo;s findings support this, as they also showed a rise in relative gluteal contribution during flexed-hip abduction \u0026mdash; especially in the upper part of the gluteus maximus, which reached its peak activation at 80\u0026deg; of flexion.⁽\u0026sup2;⁹⁾ Overall, these data reinforce the idea that hip flexion shifts recruitment toward the gluteal muscles while decreasing TFL involvement.\u003c/p\u003e \u003cp\u003eThis finding is directly relevant to clinical and strength-training practices, as exercises involving greater hip flexion during abduction can improve GMed recruitment while decreasing TFL overactivity. This strategy is useful in rehabilitation approaches that target frontal-plane instability, excessive femoral internal rotation, and lateral patellar tracking\u0026mdash;conditions linked to TFL dominance and inadequate gluteus medius activation.\u003c/p\u003e \u003cp\u003eComparison with prior studies shows partial agreement. Brandt et al. observed increased GMed activity during side-lying abduction with elastic resistance, with the hip in a neutral position, compared to seated abduction on a machine at about 90\u0026deg;, indicating that external stabilization and load type significantly affect activation levels.⁽\u0026sup2;⁴⁾ De Almeida Paz et al. reported similar GMed activation across hip flexion angles of 0\u0026deg;, 45\u0026deg;, and 90\u0026deg; when resistance loads were equalized, supporting the current study\u0026rsquo;s finding of comparable values between 45\u0026deg; and 90\u0026deg;.⁽\u0026sup2;⁶⁾ However, the present results go further by showing that at 135\u0026deg; of hip flexion, both GMed and TFL activity decrease sharply. Despite this, GMed remains a greater contributor to total abductor effort.\u003c/p\u003e \u003cp\u003eFor TFL, the current results support McBeth et al.'s findings, who reported that hip abduction performed with the hip in a neutral position and externally rotated produces higher TFL activity and lower GMed activation than abduction without rotation.⁽\u0026sup1;⁹⁾ These authors suggested that rotational and flexional positions alter the relative torque contributions of these muscles by changing their lines of action. The consistent decrease in TFL activity with hip flexion observed in this study thus supports the idea that increasing hip flexion mechanically shortens the TFL and limits its torque potential.\u003c/p\u003e \u003cp\u003eIt is worth noting that apparent discrepancies between descriptive percentage differences and inferential statistical results likely arise from methodological and analytical nuances. While the descriptive data show raw proportional changes in EMG amplitude across conditions, the inferential results are obtained from nonparametric within-subject rank-based tests adjusted for multiple comparisons. As a result, minor differences may seem statistically nonsignificant despite notable percentage changes, especially given the relatively small sample size. Nonetheless, the overall trend of change remained consistent across all analyses, supporting the robustness of the main findings.\u003c/p\u003e \u003cp\u003eFrom a practical perspective, these results suggest that performing hip abduction with moderate hip flexion (around 45\u0026deg;\u0026ndash;90\u0026deg;) may be optimal for maximizing overall gluteus medius activation. Conversely, greater hip flexion (about 135\u0026deg;) can be strategically used to selectively activate GMed over TFL, such as in corrective exercise or rehabilitation settings. The findings emphasize the importance of adjusting exercise setup not only to control overall load but also to influence relative muscle recruitment patterns and improve force distribution around the hip and pelvis.\u003c/p\u003e \u003cp\u003eThe current study has some limitations. First, although participants were carefully instructed to maintain specific hip flexion angles during each condition, they still had difficulty keeping these angles consistent throughout the entire set of repetitions. Even small deviations in joint positioning can change muscle length\u0026ndash;tension relationships and moment arms, which in turn can affect electromyographic output.\u003c/p\u003e \u003cp\u003eSecond, the investigation focused only on the tensor fasciae latae and gluteus medius, excluding other muscles that work together, such as the gluteus maximus, which also contributes to hip abduction, mainly through its upper fibers. Because the gluteus maximus undergoes significant changes in fiber orientation and moment arms during different hip positions, including this muscle in future studies could provide a more complete understanding of overall abductor mechanics.\u003c/p\u003e \u003cp\u003eThird, the maximum hip abduction amplitude for each participant was not measured, which limits the ability to determine if variability in the range of motion affected muscle activation. Additionally, due to technical issues during recording, the repetitions were analyzed as complete movement cycles instead of being separated into concentric and eccentric phases, potentially hiding phase-specific differences in neuromuscular strategy.\u003c/p\u003e \u003cp\u003eFourth, small discrepancies between descriptive and inferential statistics, especially in comparisons at 90\u0026deg; and 135\u0026deg;, reflect the natural variability of nonparametric testing with limited samples. While these differences do not alter the overall interpretation, they emphasize the need for larger, more consistent samples in future studies to confirm these trends with more robust statistical support.\u003c/p\u003e \u003cp\u003eFifth, the study sample consisted exclusively of healthy, resistance-trained young adults. Therefore, the results cannot be generalized to populations with musculoskeletal disorders, sedentary individuals, or older adults. Further research examining sex-related and pathological differences would help clarify the clinical relevance of these findings.\u003c/p\u003e \u003cp\u003eFinally, the results are specific to the mechanical setup of the abduction machine used in this study. Variations in seat tilt, pad height, backrest design, or stabilization systems on other machines could change external torque directions and influence the muscle recruitment patterns observed here. Despite these limitations, the study provides valuable insights into how different hip positions affect the neuromuscular balance between the gluteus medius and tensor fasciae latae during resistance exercise, offering a scientific foundation for more accurate hip abduction training guidelines in both clinical and performance environments.\u003c/p\u003e"},{"header":"CONCLUSIONS","content":"\u003cp\u003eThe current study showed that hip abduction at 45\u0026deg; of hip flexion resulted in greater activation of both GMed and TFL compared to 135\u0026deg;, with 90\u0026deg; producing intermediate levels. However, the 135\u0026deg; flexion condition led to the highest GMed:TFL ratio, indicating better GMed selectivity and less TFL involvement.\u003c/p\u003e \u003cp\u003eThese findings highlight the importance of hip joint position in exercise planning and suggest that performing hip abduction with increased hip flexion may more effectively target the GMed, providing a practical approach for strengthening and rehabilitating the pelvic abductors while reducing TFL dominance.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003eAuthor Contributions:\u003c/p\u003e\n\u003cp\u003eAll authors contributed equally to the conception, design, data collection, analysis, and interpretation of the study. Dr. Walter Krause Neto supervised the entire research process and prepared the final version of the manuscript. All authors reviewed, edited, and approved the final submission.\u003c/p\u003e\n\u003cp\u003eEthical Approval:\u003c/p\u003e\n\u003cp\u003eThe study was approved by the Research Ethics Committee of the State University of Par\u0026aacute; (approval no. 6.302.122) and conducted according to the Declaration of Helsinki (Fortaleza revision, 2013).\u003c/p\u003e\u003cp\u003e\u003cstrong\u003eACKNOWLEDGEMENTS\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eWe want to thank the volunteers who helped us during the collections.\u003c/p\u003e\n"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eNeumann DA. Kinesiology of the hip: a focus on muscular actions. \u003cem\u003eJ Orthop Sports Phys Ther\u003c/em\u003e. 2010;40(2):82\u0026ndash;94. doi:\u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.2519/jospt.2010.3025\u003c/span\u003e\u003cspan address=\"10.2519/jospt.2010.3025\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003ePowers CM. The influence of abnormal hip mechanics on knee injury: a biomechanical perspective. \u003cem\u003eJ Orthop Sports Phys Ther.\u003c/em\u003e 2010;40(2):42\u0026ndash;51.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eStrauss EJ, Nho SJ, Kelly BT. Greater trochanteric pain syndrome. \u003cem\u003eSports Med Arthrosc Rev.\u003c/em\u003e 2010;18(2):113\u0026ndash;119.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eNakagawa TH, Moriya ET, Maciel CD, Serr\u0026atilde;o FV. Trunk, pelvis, hip, and knee kinematics, hip strength, and gluteal muscle activation during a single-leg squat in males and females with and without patellofemoral pain syndrome. \u003cem\u003eJ Orthop Sports Phys Ther\u003c/em\u003e. 2012;42(6):491\u0026ndash;501.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eBuckthorpe M, Stride M, Della Villa F. Assessing and treating gluteus maximus weakness: a clinical commentary. \u003cem\u003eInt J Sports Phys Ther.\u003c/em\u003e 2019;14(4):655\u0026ndash;669.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eFrench HP, Dunleavy M, Cusack T. Predictors of functional capacity in older adults with osteoarthritis of the hip. \u003cem\u003ePhys Ther.\u003c/em\u003e 2010;90(9):1251\u0026ndash;1262.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eHinman RS, Hunt MA, Creaby MW, Wrigley TV, McManus FJ, Bennell KL. Hip muscle weakness in individuals with knee osteoarthritis. \u003cem\u003eArthritis Care Res (Hoboken)\u003c/em\u003e. 2010;62(8):1190\u0026ndash;1198.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eFredericson M, Cookingham CL, Chaudhari AM, Dowdell BC, Oestreicher N, Sahrmann SA. Hip abductor weakness in distance runners with iliotibial band syndrome. \u003cem\u003eClin J Sport Med.\u003c/em\u003e 2000;10(3):169\u0026ndash;175.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLee SP, Souza RB, Powers CM. The influence of hip abductor muscle performance on dynamic postural stability in females with patellofemoral pain. \u003cem\u003eGait Posture.\u003c/em\u003e 2012;36(3):425\u0026ndash;429. doi:\u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1016/j.gaitpost.2012.03.014\u003c/span\u003e\u003cspan address=\"10.1016/j.gaitpost.2012.03.014\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eCalais-Germain B. \u003cem\u003eAnatomy of Movement\u003c/em\u003e. Seattle, WA: Eastland Press; 1993.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSahrmann SA. \u003cem\u003eDiagnosis and Treatment of Movement Impairment Syndromes\u003c/em\u003e. St. Louis, MO: Mosby; 2001.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMerican AM, Amis AA. Iliotibial band tension affects patellofemoral and tibiofemoral kinematics. \u003cem\u003eJ Biomech.\u003c/em\u003e 2009;42(10):1539\u0026ndash;1546. doi:\u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1016/j.jbiomech.2009.03.041\u003c/span\u003e\u003cspan address=\"10.1016/j.jbiomech.2009.03.041\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eBesomi M, Maclachlan L, Mellor R, Vicenzino B, Hodges PW. Tensor fascia latae muscle structure and activation in individuals with lower limb musculoskeletal conditions: a systematic review and meta-analysis. \u003cem\u003eSports Med.\u003c/em\u003e 2020;50:1\u0026ndash;21. doi:\u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1007/s40279-019-01251-1\u003c/span\u003e\u003cspan address=\"10.1007/s40279-019-01251-1\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSelkowitz DM, Beneck GJ, Powers CM. Which exercises target the gluteal muscles while minimizing activation of the tensor fascia lata? Electromyographic assessment using fine-wire electrodes. \u003cem\u003eJ Orthop Sports Phys Ther\u003c/em\u003e. 2013;43(2):54\u0026ndash;64. doi:\u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.2519/jospt.2013.4116\u003c/span\u003e\u003cspan address=\"10.2519/jospt.2013.4116\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSidorkewicz N, Cambridge ED, McGill SM. Examining the effects of altering hip orientation on gluteus medius and tensor fascia latae interplay during common non-weight-bearing hip rehabilitation exercises. \u003cem\u003eClin Biomech (Bristol, Avon)\u003c/em\u003e. 2014;29(9):971\u0026ndash;976. doi:\u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1016/j.clinbiomech.2014.09.002\u003c/span\u003e\u003cspan address=\"10.1016/j.clinbiomech.2014.09.002\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eBishop BN, Greenstein J, Etnoyer-Slaski JL, Hornsby E, Conrad K, Ingersoll CD. Electromyographic analysis of gluteus maximus, gluteus medius, and tensor fascia latae during therapeutic exercises with and without elastic resistance. \u003cem\u003eInt J Sports Phys Ther\u003c/em\u003e. 2018;13(4):668\u0026ndash;675.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eWillcox EL, Burden AM. The influence of varying hip angle and pelvis position on muscle recruitment patterns of the hip abductor muscles during the clam exercise. \u003cem\u003eJ Orthop Sports Phys Ther\u003c/em\u003e. 2013;43(5):325\u0026ndash;331. doi:\u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.2519/jospt.2013.4004\u003c/span\u003e\u003cspan address=\"10.2519/jospt.2013.4004\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eChan MK, Chow KW, Lai AY, Mak NK, Sze JC, Tsang SM. The effects of therapeutic hip exercise with abdominal core activation on recruitment of the hip muscles. \u003cem\u003eBMC Musculoskelet Disord.\u003c/em\u003e 2017;18(1):313. doi:\u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1186/s12891-017-1674-2\u003c/span\u003e\u003cspan address=\"10.1186/s12891-017-1674-2\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMcBeth JM, Earl-Boehm JE, Cobb SC, Huddleston WE. Hip muscle activity during three side-lying hip-strengthening exercises in distance runners. \u003cem\u003eJ Athl Train.\u003c/em\u003e 2012;47(1):15\u0026ndash;23. doi:\u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.4085/1062-6050-47.1.15\u003c/span\u003e\u003cspan address=\"10.4085/1062-6050-47.1.15\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eTsang SMH, Lam AHM, Ng MHL, Ng KWK, Tsui COH, Yiu B. Abdominal muscle recruitment and its effect on the activity level of the hip and posterior thigh muscles during therapeutic exercises of the hip joint. \u003cem\u003eJ Electromyogr Kinesiol.\u003c/em\u003e 2018;42:10\u0026ndash;19. doi:\u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1016/j.jelekin.2018.06.005\u003c/span\u003e\u003cspan address=\"10.1016/j.jelekin.2018.06.005\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eCaon G, Silva T, Pereira L, et al. Exerc\u0026iacute;cios terap\u0026ecirc;uticos mais eficientes na ativa\u0026ccedil;\u0026atilde;o de gl\u0026uacute;teo m\u0026aacute;ximo e gl\u0026uacute;teo m\u0026eacute;dio: revis\u0026atilde;o de literatura. \u003cem\u003eSa\u0026uacute;de Desenvol Hum.\u003c/em\u003e 2020;8(2):139\u0026ndash;150.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eFrigotto MF, Cardoso CA, Santos RR, Rodrigues R. Gluteus medius and tensor fascia latae muscle activation levels during multi-joint strengthening exercises. \u003cem\u003eMotriz Rev Educ Fis.\u003c/em\u003e 2019;25:e0030011. doi:\u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1590/s1980-6574201900030011\u003c/span\u003e\u003cspan address=\"10.1590/s1980-6574201900030011\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eBrandt M, Jakobsen MD, Thorborg K, Sundstrup E, Jay K, Andersen LL. Perceived loading and muscle activity during hip strengthening exercises: comparison of elastic resistance and machine exercises. \u003cem\u003eInt J Sports Phys Ther\u003c/em\u003e. 2013;8(6):811\u0026ndash;819. PMID:24377067; PMCID:PMC3867074\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eDelp SL, Hess WE, Hungerford DS, Jones LC. Variation of rotation moment arms with hip flexion. \u003cem\u003eJ Biomech.\u003c/em\u003e 1999;32(5):493\u0026ndash;501. doi:\u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1016/S0021-9290(99)00032-9\u003c/span\u003e\u003cspan address=\"10.1016/S0021-9290(99)00032-9\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003ede Almeida Paz I, Frigotto MF, Cardoso CA, Rabello R, Rodrigues R. Hip abduction machine is better than free weights to target the gluteus medius while minimizing tensor fascia latae activation. \u003cem\u003eJ Bodyw Mov Ther.\u003c/em\u003e 2022;30:160\u0026ndash;167. doi:\u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1016/j.jbmt.2022.01.001\u003c/span\u003e\u003cspan address=\"10.1016/j.jbmt.2022.01.001\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLeis AA, Trapani VC. \u003cem\u003eAtlas of Nerve Conduction Studies and Electromyography\u003c/em\u003e. 3rd ed. New York, NY: Oxford University Press; 2013.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eHo J, Tumkaya T, Aryal S, Choi H, Claridge-Chang A. Moving beyond P values: data analysis with estimation graphics. \u003cem\u003eNat Methods.\u003c/em\u003e 2019;16(7):565\u0026ndash;566. doi:\u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1038/s41592-019-0470-3\u003c/span\u003e\u003cspan address=\"10.1038/s41592-019-0470-3\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eFujisawa H, Suzuki H, Yamaguchi E, Yoshiki H, Wada Y, Watanabe A. Hip muscle activity during isometric contraction of hip abduction. \u003cem\u003eJ Phys Ther Sci.\u003c/em\u003e 2014;26(2):187\u0026ndash;190. doi:\u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1589/jpts.26.187\u003c/span\u003e\u003cspan address=\"10.1589/jpts.26.187\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":true,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":true,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"gluteus medius, tensor fasciae latae, hip abduction, electromyography, resistance training","lastPublishedDoi":"10.21203/rs.3.rs-8523653/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-8523653/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eUnderstanding how joint position influences muscle recruitment is essential for improving exercise prescription. This study examined how different hip flexion angles affect the electromyographic (EMG) activity of the gluteus medius (GMed) and tensor fasciae latae (TFL) during seated hip abduction \u0026mdash; a popular movement in resistance training and rehabilitation. Fourteen recreationally trained volunteers performed the exercise at 45\u0026deg;, 90\u0026deg;, and 135\u0026deg; of hip flexion, with the load set at 60% of their individual six-repetition maximum (6RM). Surface EMG signals of GMed and TFL were recorded and normalized to maximal voluntary isometric contraction (%MVIC). Data were analyzed using Friedman\u0026rsquo;s test and Dunn\u0026rsquo;s post hoc comparisons (p\u0026thinsp;\u0026lt;\u0026thinsp;0.05), with effect sizes (Hedges\u0026rsquo; g) and 95% confidence intervals calculated via the Estimation Stats platform. Results showed a clear pattern: increased hip flexion significantly decreased TFL activation while maintaining moderate GMed activity. Peak and average GMed activation were notably higher at 45\u0026deg; compared to 135\u0026deg; (p\u0026thinsp;\u0026lt;\u0026thinsp;0.001), whereas TFL activation decreased progressively across 45\u0026deg;, 90\u0026deg;, and 135\u0026deg; (all p\u0026thinsp;\u0026lt;\u0026thinsp;0.01). Most importantly, the GMed:TFL activation ratio tripled at 135\u0026deg;, indicating a significant shift toward targeted GMed recruitment and reduced TFL dominance. Therefore, increasing hip flexion during seated abduction enhances the neuromuscular selectivity of the gluteus medius while reducing tensor fasciae latae overactivation \u0026mdash; a finding with direct implications for both hypertrophy-focused training and clinical rehab. These findings redefine how a simple change in hip angle can transform one of the most common lower-body exercises.\u003c/p\u003e","manuscriptTitle":"Not All Hip Abductions Are Equal: The 45° Paradox Between Gluteus Medius and Tensor Fasciae Latae","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-01-06 10:34:21","doi":"10.21203/rs.3.rs-8523653/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"f621fc61-95bc-46d1-b3f1-04684f99f610","owner":[],"postedDate":"January 6th, 2026","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2026-04-05T14:18:27+00:00","versionOfRecord":[],"versionCreatedAt":"2026-01-06 10:34:21","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-8523653","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-8523653","identity":"rs-8523653","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}