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Background: Injuries of the hip extensors are not uncommon, with those of the hamstrings being frequent among athletes. On the contrary, isolated injuries of the gluteus maximus muscle have been barely reported in the literature. Case Report: We present a case of a 63-year-old male water aerobics trainer with an acute tear of the right gluteus maximus tendon and describe the clinical presentation, imaging studies, surgical treatment, and functional outcome one year after surgery.

The gluteus medius (GM) muscle in quadrupedal primates has long been thought to mainly act as a hip extensor. However, previous reports argue that it may be a prime hip medial rotator and functions to rotate the pelvis in the horizontal plane, suggesting the functional differentiation between the GM and other hip extensors as hamstrings. In this study, we aim to quantify the muscle actions of the GM and hamstrings using muscle moment arm lengths and discuss the functional differentiation among hip extensors. Muscle attachment sites of eight specimens of Japanese macaque (Macaca fuscata) were digitized, and musculoskeletal models were constructed. Flexor‐extensor, abductor‐adductor, and medial‐lateral rotator moment arms were calculated as the models were moved following the experimentally acquired kinematic data during walking on a pole substrate. Using electromyography, we also recorded the pattern of muscle activation. The GM showed a larger medial rotator moment arm length than the extensor moment arm length when it was activated, suggesting this muscle acts mainly as a hip medial rotator rather than as a hip extensor. The medial rotator action of the GM in the early support phase may rotate the pelvis in the horizontal plane and function to help contralateral forelimb reaching as a previous study suggested and facilitate contralateral hindlimb swinging to place the foot near the ipsilateral forelimb's hand. [ABSTRACT FROM AUTHOR]

The global application of horizontal force (FH) via hip extension is related to improvements in sprint performance (eg, maximal velocity [vmax] and power [Pmax]). Little is known regarding the contribution of individual leg FH and how a difference between the legs (asymmetry) might subsequently affect sprint performance. The authors assessed a single male athlete for pre-post outcomes of a targeted hip-extension training program on FH asymmetry and sprint-performance metrics. An instrumented nonmotorized treadmill was used to obtain individual leg and global sprint kinetics and determine the athlete's strong and weak leg, with regard to the ability to produce FH while sprinting. Following a 6-wk control block of testing, a 6-wk targeted training program was added to the athlete's strength-training regimen, which aimed to strengthen the weak leg and improve hip-extension function during sprinting. Preintervention to postintervention, the athlete increased FH (standardized effect [ES] = 2.2; +26%) in his weak leg, decreased the FH asymmetry (ES = -0.64; -19%), and increased vmax (ES = 0.67; +2%) and Pmax (ES = 3.2; +15%). This case study highlighted a promising link between a targeted training intervention to decrease asymmetry in FH and subsequent improvement of sprint-performance metrics. These findings also strengthen the theoretical relationship between the contribution of individual leg FH and global FH while sprinting, indicating that reducing asymmetry may decrease injury risk and increase practical performance measures. This case study may stimulate further research investigating targeted training interventions in the field of strength and conditioning and injury prevention. [ABSTRACT FROM AUTHOR]

OBJECTIVE: Dynamic hip stabilizers are essential for optimal performance in football players, particularly during kicking. Although the muscle strength deficits of hip muscles as an etiology of osteitis pubis (OP) in football players have not yet been well investigated, previous assessments give more attention to the concentric mode of strength for both hip flexor and extensor muscles. Functionally, the hip muscles interact in an eccentric/concentric pattern. This study aimed to compare the concentric, eccentric, and eccentric antagonist/concentric agonist ratios for hip flexor and extensor strength between football players with OP and healthy athletes PATIENTS AND METHODS: Thirty-four male footballers with OP and eighteen healthy footballers were tested using an isokinetic dynamometer at a speed of 180°/s. RESULTS: Football players with osteitis pubis demonstrated a significantly lower eccentric extensor/concentric flexor ratio and higher eccentric hip flexor/extensor ratio (p < 0.05) when compared with healthy participants. CONCLUSIONS: The present study demonstrated that football players with OP had a reduced capability to produce eccentric hip extension torque compared to healthy athletes. Consequently, the eccentric rather than the concentric weakness of hip extensors could be suggested as one of the intrinsic contributing factors for OP. Incorporating findings of the current study in clinical practice could afford critical information while evaluating the hip muscles in football players with OP for pre-screening, developing rehabilitation programs, and guiding the decision to return to sports after injury. [ABSTRACT FROM AUTHOR]

The purpose of the study was to compare the normalized-electromyographic (NEMG) activity of the gluteus maximus (GMAX), gluteus medius (GMED), biceps femoris (BF) and erector spinae (ES) muscles during the single-leg deadlift (SLDL) and the conventional-deadlift (DL). Additionally, a potential influence of body height on the NEMG activity was examined. Fifteen training-experienced male subjects completed the study. SLDL showed significantly higher average concentric NEMG values of the GMED (77.6% vs. 59.3% [p = 0.002, ES = 1.0]) and BF (82.1% vs. 74.2% [p = 0.041, ES = 0.6]). Significantly lower NEMG levels were found only in the left strand of the ES muscle (67.2% vs. 82.7% [p = 0.004, ES = 0.9]). A significant influence of body height on EMG activity was also observed for all muscles, with the exception of the GMED, during the SLDL. Body height correlated negatively with the concentric EMG activity of the ES (r = -0.54 to -0.58), the BF (r = -0.63) and the GMAX (r = -0.85). In the DL there was a negative correlation only in the BF (r = -0.59) and the GMAX (r = -0.7). This means that subjects with a lower body height showed a higher NEMG activity in corresponding muscles. The results of this study indicate that the SLDL is preferable to the DL in training the BF, and GMED. In addition, coaches should be aware that athletes body height can influence the extent to which the respective muscles are activated. [ABSTRACT FROM AUTHOR]

This study investigated the activity of surface electromyography (sEMG) on trunk and pelvic muscles during supine bridge exercise (SBE) with different knee flexion angles. Twenty-five physically active males participated in this study. Subjects received maximum voluntary isometric contraction (MVIC) tests followed by four SBEs with different knee flexion angles (40°, 60°, 90° and 120°) in random. sEMG activities of rectus abdominis (RA), erector spinae (ER), gluteus medius (GMed), superior gluteus maximus (SGMax), inferior gluteus maximus (IGMax), biceps femoris (BF) long head, and the ratio of SGMax/BF and IGMax/BF on the dominant side were measured. Non-clinical magnitude-based inference was performed to compare the effect. The results indicated a substantial change of muscle activity, especially between SBE with 40° and 120° knee flexion. With respect to ER and BF, moderate effect (−0.70 ± 0.17) and extremely large effect (−4.78 ± 0.51) were recorded, whereas very large effect for SGMax/BF (2.68 ± 0.23) and IGMax/BF (2.95 ± 0.26) was observed, respectively. Both ER and BF worked better with smaller knee flexion angles (40° > 60° > 90° > 120°), while SGMax and IGMax were more favourable to SBE with large knee flexion angles (90° = 120° > 60° > 40°). [ABSTRACT FROM AUTHOR]

Purpose: This study was aimed to identify correlation between maximum isometric strength in five muscle groups determined by dynamometry results of muscle tests and the inclination angles of the spine.Methods: This predictive correlational study included 63 young healthy athletes aged 10-15. (m/f 31/32; 12.73 ± 1.58 years; 162.57 ± 12.94 cm; 52.86 ± 12.17 kg; 3.95 ± 1.70 training years; 4.05 ± 1.31 training h/week).The maximum isometric strength in five muscle groups was measured by a handheld dynamometer with external belt fixation using a portable stabilization device. The inclination angles were measured with a digital inclinometer. The data were analyzed using descriptive statistics, and correlations were estimated by Pearson's correlation coefficient (r).Results: The isometric muscular strength of the muscle group of the hip extensors was in a significant correlation with the lumbar lordosis angle (LLA), r = 0.714 (p < 0.0001). The isometric muscular strength of the muscle group of the erector spinae was in a significant correlation with the LLA, r = 0.578 (p < 0.0001) and with thoracic kyphosis angle (TKA), r = 0.522 (p < 0.0001).Conclusion: There is a strong association between isometric strength of the muscle groups of the hip extensors and erector spinae and the inclination angles of the spine. Based on the isometric results, physical therapy can be proposed for increasing the muscular strength of those muscle groups, which can help in the prevention of more severe forms of postural deformities. These slides can be retrieved under Electronic Supplementary Material. [ABSTRACT FROM AUTHOR]

Abstract Background It has been found that alterations in passive muscle properties may be associated with low back pain, and these may be responsible for the altered gait parameters often observed in subjects with back pain. The purpose of the present study was to assess total hip and passive hip extensor moments in people with or without low back pain during the hip flexion component of walking. Methods 52 subjects volunteered for this study (low back pain group, n = 25 (male n = 13, female n = 12), control group, n = 27 (male n = 15, female n = 12)). Passive hip moments were calculated using an adapted force transducer during supine testing. A biomechanical model and predictive equation were used to calculate passive hip moments during walking. Total hip moments were calculated with the use of a 9 camera, 3-D motion-capture system. Findings Independent samples t -tests demonstrated no significant differences between groups for gait parameters or hip or knee angles. Results of the ANOVAs demonstrated significant differences in passive hip flexor moments during the second half of hip flexion (P < 0.05).There were also significant differences in hip power and work done during peaks of power absorption and the second peak of power generation (P < 0.05). Interpretation The present data demonstrates that subjects with low back pain have altered passive hip extensor and total power and work done during walking compared with healthy controls. Biomechanical models should include individual measurements of passive joint moments. Highlights • Low back pain is one of the leading causes of disability globally. • Passive muscle properties may be associated with low back pain. • Total hip moments, power and work done are affected by low back pain. • Interventions should differentiate between passive and active factors. [ABSTRACT FROM AUTHOR]

This study aimed to compare the muscle activity of lower limbs across typical table tennis strokes. Fourteen high-level players participated in this study in which five typical strokes (backhand top, forehand top, forehand spin, forehand smash, flick) were analysed. Surface electromyography activity (EMG) of eight muscles was recorded (gluteus maximus, biceps femoris, vastus medialis, vastus lateralis, rectus femoris, gastrocnemius medialis, gastrocnemius lateralis, soleus) and normalised to the maximal activity measured during squat jump or isometric maximal voluntary contractions. The forehand spin, the forehand top and the forehand smash exhibited significant higher EMG amplitude when compared with other strokes. Both biceps femoris and gluteus maximus were strongly activated during the smash, forehand spin and forehand top (from 62.8 to 91.7% of maximal EMG activity). Both vastii and rectus femoris were moderately to strongly activated during the forehand spin (from 50.4 to 62.2% of maximal EMG activity) whereas gastrocnemii and soleus exhibited the highest level of activity during the smash (from 67.1 to 92.1% of maximal EMG activity). Our study demonstrates that offensive strokes, such as smash or forehand top, exhibit higher levels of activity than other strokes. [ABSTRACT FROM AUTHOR]

The purpose of this study was to compare the gluteus maximus (GM) and hamstring group (HG) electromyographic (EMG) activation levels among selected weight-bearing resistance exercises. Eighteen young adult females with previous resistance training experience completed the study. Strength was assessed on the bilateral squat (BS) (3 repetition maximum [RM]), modified single-leg squat (MSLS) (3RM), and stiff-leg deadlift (SLDL) (8RM) to determine an 8RM load for all lifts. Surface EMG was collected after 48 hours of rest using wireless Trigno IM Sensors using EMMA software (Delsys), which also collected and synchronized 3D hip and knee motion. A maximum voluntary isometric contraction was determined for the GM and HG to normalize the EMG data. During EMG data collection, 3 repetitions were completed using an 8RM load on all 3 exercises. Gluteus maximus EMG was significantly greater than HG EMG on the BS (40.3 vs. 24.4%, p < 0.001), MSLS (65.6 vs. 40.1 %, p < 0.012), and SLDL (40.5 vs. 29.9 %, p < 0.047). The MSLS produced significantly greater HG EMG (p = 0.001) compared with the SLDL, whereas the SLDL was significantly greater (p = 0.004) than the BS. The MSLS GM EMG was also significantly greater (p < 0.001) than the SLDL and BS, whereas no difference was found between the SLDL and BS. Comparing the activation of the 2 muscle groups in all exercises, the GM seems to be the primary muscle recruited whereas the MSLS seems to produce greater GM and HG activation. The data indicate that it would be most beneficial to include the MSLS during GM and HG training. [ABSTRACT FROM AUTHOR]

Low back pain (LBP) is a common complaint among field hockey players. Only a few of the risk factors for LBP have however been assessed on these players. These include trunk strength and lumbosacral range of motion. The aim of the literature review was therefore to investigate the reports of LBP among elite female field hockey players, focusing on risk factors for LBP, biomechanical aspects of field hockey, muscle imbalance and the role of the gluteus maximus (GM) muscle in the development of LBP. The literature indicated a strong link between LBP and GM weakness. More recent research supports this concept and clearly stated that female athletes with GM weakness are at risk for the development of LBP. Considering that the biomechanical aspects and unique requirements of field hockey indicate hip extensor involvement, as well as the association between LBP and GM weakness, further investigation is warranted into the hip extensor muscles of field hockey players.

STUDIES SUPPORT THE USE OF KETTLEBELLS FOR IMPROVING POWER, ALTHOUGH EVIDENCE FOR USING THEM TO IMPROVE STRENGTH AND AEROBIC FITNESS IS STILL EQUIVOCAL. STUDIES INVESTIGATING THE BIOMECHANICAL PROPERTIES OF KETTLEBELL TRAINING HAVE BEEN FRUITFUL, AND IT MAY BE USEFUL FOR DEVELOPING SPRINT RUNNING PERFORMANCE AND FOR INJURY PREVENTION. HOWEVER, WE STILL DO NOT KNOW THE OPTIMAL LOADS FOR MAXIMIZING SYSTEM AND JOINT POWER PRODUCTION, HOW THE MECHANICS, JOINT MOMENTS, AND ELECTROMYOGRAPHIC ACTIVITY CHANGES AS LOADS INCREASE DURING KETTLEBELL SWINGS, NOR WHETHER KETTLEBELL TRAINING TRANSFERS TO SPORTS PERFORMANCE. [ABSTRACT FROM AUTHOR]

HIP EXTENSION MOMENTS INCREASE TO A MUCH GREATER DEGREE THAN KNEE EXTENSION MOMENTS WITH INCREASING LOADS DURING THE SQUAT, LUNGE, AND DEADLIFT EXERCISES AND WITH INCREASING RUNNING SPEEDS, JUMP HEIGHTS, AND LATERAL AGILITY MANEUVERS. THEREFORE, HIP EXTENSION TRAINING SHOULD BE PRIORITIZED IN ATHLETIC CONDITIONING BY (A) USING HIP-DOMINANT EXERCISES IN THE ATHLETE'S PROGRAM, (B) EMPHASIZING HEAVIER LOADS DURING COMPOUND LOWER-BODY RESISTANCE EXERCISES AS THE ATHLETE MATURES, AND (C) INCORPORATING LOADS THAT MAXIMIZE THE HIP EXTENSION MOMENT DURING EXPLOSIVE LOWER-BODY TRAINING. [ABSTRACT FROM AUTHOR]

TARGETED HIP EXTENSION EXERCISES ARE OFTEN PERFORMED TO DEVELOP STRENGTH, POWER, AND ENDURANCE IN THE HIP EXTENSORS. ALTHOUGH THESE EXERCISES CAN POSSESS SIMILAR MOVEMENT PATTERNS, BIOMECHANICALLY THE INSTANTANEOUS TORQUE AT DIFFERENT RANGES OF HIP EXTENSION VARIES DEPENDING ON BODY POSITION RELATIVE TO SPACE. FOR THESE REASONS, IT IS PROPOSED THAT: (A) HIP EXTENSION EXERCISES MIGHT TRANSFER BETTER TO SPORT ACTIONS WHERE THE REGION OF FORCE ACCENTUATION IS MOST SPECIFIC; (B) HIP EXTENSION EXERCISES MAY LEAD TO UNIQUE STRUCTURAL ADAPTATIONS; AND (C) A VARIETY OF EXERCISES MIGHT BE NECESSARY TO MAXIMIZE HIP EXTENSION STRENGTH AND POWER THROUGHOUT THE ENTIRE RANGE OF MOTION. [ABSTRACT FROM AUTHOR]

Paraspinal muscle fatigability during various trunk extension tests has been widely investigated by electromyography (EMG), and its task-dependency is established recently. Hip extensor muscle fatigability during the Sorensen test has been reported. The aim of the present experiments was to evaluate the task-dependency of back and hip extensor muscle fatigue during two variants of the Sorensen test. We hypothesized that the rate of muscular fatigue of the hip and back extensor muscles varies according to the test position. Twenty healthy young males with no history of low back pain volunteered to participate in this cross-sectional study. They were asked to perform two body weight-dependent isometric back extension tests (S1 = Sorensen test; S2 = modified Sorensen on a 45° Roman chair). Surface EMG activity of the paraspinal muscles (T10 and L5 levels) and hip extensor muscles (gluteus maximus; biceps femoris) was recorded, and muscular fatigue was assessed through power spectral analysis of the EMG data by calculating the rate of median power frequency change. We observed hip extensor muscle fatigue simultaneously with paraspinal muscle fatigue during both Sorensen variants. However, only L5 level EMG fatigue indices showed a task-dependency effect between S1 and S2. Hip extensor muscles appear to contribute to load sharing of the upper body mass during both Sorensen variants, but to a different extent because L5 level fatigue differs between the Sorensen variants. Our findings suggest that task-dependency has to be considered when EMG variables are compared between two types of lumbar muscle-fatiguing tasks. [ABSTRACT FROM AUTHOR]