Hip Extensor Activity Research Articles

Altered Hip Flexor and Extensor Activation During Progressive Inclined Walking in Individuals With Femoroacetabular Impingement Syndrome

Context: Femoroacetabular impingement syndrome (FAIS) is a movement-related condition associated with pain and impaired function; yet the evidence for level ground walking hip biomechanics is limited and inconsistent. Challenging the hip with inclined walking for individuals with FAIS might be important for elucidating mechanically driven function loss and informing tailored rehabilitation. The purpose of this study was to determine the effects of progressive inclined walking on sagittal hip biomechanics and hip flexor and extensor activity in individuals with FAIS. Design: Cross-sectional. Methods: Fourteen participants (7 individuals with FAIS and 7 asymptomatic individuals) underwent motion capture and electromyographic analysis during 3 treadmill walking conditions (0°/5°/10°). Statistical parametric mapping was used to compare the sagittal hip kinematic waveforms and hip flexor (rectus femoris) and extensor (gluteus maximus) waveforms between groups and walking conditions. Results: Hip flexion was significantly increased throughout the gait cycle in individuals with FAIS compared with asymptomatic individuals (P < .01) but was not dependent on incline. Rectus femoris activation was significantly increased throughout stance in individuals with FAIS compared with asymptomatic individuals (P < .01). Gluteus maximus activity significantly increased with progressive inclination in asymptomatic individuals (P < .01), with no significant change in activity for individuals with FAIS. Conclusions: Hip biomechanics and muscle activity during inclined walking mirrored that of arthrogenic muscle inhibition, highlighted by a prominent flexor role and lack of hip extensor activity in individuals with FAIS. Future research investigating discordant activity between hip flexors and extensors during complex functional tasks may help identify rehabilitation targets.

The Effects of Ankle Joint Position on Hip Extensor Muscle Activity for Bridging Exercise in Sagittal Plane

The Effects of Ankle Joint Position on Hip Extensor Muscle Activity for Bridging Exercise in Sagittal Plane

Effects of passive exoskeleton on trunk and gluteal muscle activity, spinal and hip kinematics and perceived exertion for physiotherapists in a simulated chair transfer task: A feasibility study

Despite being a topic of increasing concern, work-related musculoskeletal disorders (WMSDs) among physiotherapists, have not been comprehensively explored. This study evaluated the effects of using a passive exoskeleton on biomechanics (i.e. muscle activity of back and hip extensors) and kinematics (trunk and hip flexion angles) during a simulated chair transfer task. A simulated patient was used for the chair transfer task. Twenty working physiotherapists performed the chair transfer task with or without using a passive exoskeleton. The biomechanics and kinematics during the tasks were measured using surface electromyography (sEMG) and motion sensors, respectively. Change in exertion level was examined using the Borg CR-10 scale, and an acceptance questionnaire was adopted from previous studies and used in investigating user acceptance of the exoskeleton. Results revealed that (1) using a passive exoskeleton in performing transfer tasks significantly decreased the sEMG activities of thoracic erector spinae, lumbar erector spinae and gluteal muscles, decreasing the maximum voluntary isometric contraction by 7.78%–10.95%; (2) no significant differences in the maximal flexion angles of thoracic and lumbar spines and trunk between performing the task with and without the exoskeleton; (3) a nonsignificant decrease in exertion level when performing the transfer task with the exoskeleton; and (4) no significant between-group differences in the score of acceptance questionnaire. These findings suggested that using the exoskeleton may help alleviate loading on the back by decreasing back extensor and hip extensor muscle activities while not considerably changing sagittal plane kinematics at the trunk and hip.

Compensatory Responses During Slip-Induced Perturbation in Patients With Knee Osteoarthritis Compared With Healthy Older Adults: An Increased Risk of Falls?

Background: Functional impairment of the knee joint affected by osteoarthritis and loss of muscle strength leads to a significant increase in the number of falls. Nevertheless, little is known about strategies for coping with gait perturbations in patients with knee osteoarthritis (KOA). Thus, this study aimed to examine the compensatory strategies of patients with KOA in response to a backward slip perturbation compared with healthy older adults. Methods: An automated perturbation program was developed by using D-Flow software based on the Gait Real-time Analysis Interactive Lab, and an induced backward slip perturbation was implemented on nine patients with severe KOA (68.89 ± 3.59 years) and 15 age-matched healthy older adults (68.33 ± 3.29 years). Step length, gait speed, range of motion, vertical ground reaction forces, lower extremity joint angles, and joint moments were computed and analyzed. Results: Compared with older adults, patients with KOA had significantly lower step length, gait speed, and vertical ground reaction forces in both normal walking and the first recovery step following backward slip perturbations. Inadequate flexion and extension of joint angles and insufficient generation of joint moments predispose patients with KOA to fall. Hip extension angle and flexion moment, knee range of motion, and vertical ground reaction forces are key monitoring variables. Conclusion: The risk of falls for patients with KOA in response to backward slip perturbations is higher. Patients with KOA should focus not only on quadriceps muscle strength related to knee range of motion but also on improving hip extensor strength and activation through specific exercises. Targeted resistance training and perturbation-based gait training could be better options.

Using a Passive Back Exoskeleton During a Simulated Sorting Task: Influence on Muscle Activity, Posture, and Heart Rate.

To evaluate using a back exoskeleton in a simulated sorting task in a static forward bent trunk posture on muscle activity, posture, and heart rate (HR). Potentials of exoskeletons for reducing musculoskeletal demands in work tasks need to be clarified. Thirty-six healthy males performed the sorting task in 40°-forward bent static trunk posture for 90seconds, in three trunk orientations, with and without exoskeleton. Muscle activity of the erector spinae (ES), biceps femoris (BF), trapezius descendens (TD), rectus abdominis (RA), vastus laterals (VL), and gastrocnemius medialis was recorded using surface electromyography normalized to a submaximal or maximal reference electrical activity (%RVE (reference voluntary electrical activity)/%MVE). Spine and lower limb postures were assessed by gravimetric position sensors, and HR by electrocardiography. Using the exoskeleton resulted in decreased BF muscle activity [-8.12%RVE], and minor changes in ES [-1.29%MVE], RA [-0.28%RVE], VL [-0.49%RVE], and TD [+1.13%RVE] muscle activity. Hip and knee flexion increased [+8.1°; +6.7°]. Heart rate decreased by 2.1 bpm. Trunk orientation had an influence on BF muscle activity. Using the back exoskeleton in a short sorting task with static trunk posture mainly reduced hip extensor muscle activity and changed lower limb but not spine posture. Implications of using a back exoskeleton for workers' musculoskeletal health need further clarification. The detected changes by using the Laevo® illustrate the need for further investigation prior to practical recommendations of using exoskeletons in the field. Investigating various work scenarios in different kind of workers and long-term applications would be important elements.

고관절 외전 각도가 리버스 하이퍼 익스텐션 운동 시 근활성도에 미치는 영향

The purpose of this study was to investigate whether different hip abduction angles might alternate hip extensor muscle activity in reverse hyperextension (RHE) exercise. Fourteen healthy male subjects performed RHE in 4 hip abduction angles (-10°, 0°, 15°, and 30°). Muscle activities of longissimus, gluteus maximus, gluteus medius, biceps femoris, semitendinosus, and adductor magnus were measured by surface electromyography device. One-way repeated ANOVA was used to analyze the results from each angle of muscle and the ratio of muscle activation. During the concentric phase of RHE, gluteus medius activation was greater at 15° and 30° of hip abduction angles (p.001) than at -10 and 0°, while biceps femoris was greatest at -10° (p.001) followed by 0°, 15°, and 30° of hip abduction angles. During the eccentric phase of RHE, gluteus medius activation was greater at 15° and 30° of hip abduction angles (p.003) than -10°, while biceps femoris was greatest at -10° (p.001) followed by 15° and 30°. Our findings suggest that RHE of hip abduction at 15° and 30° might be the most appropriate angle for maximizing gluteal muscle activation.

The Effects of Gluteal Strength and Activation on the Relationship Between Femoral Alignment and Functional Valgus Collapse During a Single-Leg Landing.

A bias toward femoral internal rotation is a potential precursor to functional valgus collapse. The gluteal muscles may play a critical role in mitigating these effects. Determine the extent to which gluteal strength and activation mediate associations between femoral alignment measures and functional valgus collapse. Cross-sectional. Research laboratory. Forty-five females (age = 20.1 [1.7]y; height = 165.2 [7.6]cm; weight = 68.6 [13.1]kg) and 45 males (age = 20.8 [2.0]y; height = 177.5 [8.7]cm; weight = 82.7 [16.5]kg), healthy for 6 months prior. Femoral alignment was measured prone. Hip-extension and abduction strength were obtained using a handheld dynamometer. Three-dimensional biomechanics and surface electromyography were obtained during single-leg forward landings. Forward stepwise multiple linear regressions determined the influence of femoral alignment on functional valgus collapse and the mediating effects of gluteus maximus and medius strength and activation. In females, less hip abduction strength predicted greater peak hip adduction angle (R2 change = .10; P = .02), and greater hip-extensor activation predicted greater peak knee internal rotation angle (R2 change = .14; P = .01). In males, lesser hip abduction strength predicted smaller peak knee abduction moment (R2 change = .11; P = .03), and the combination of lesser hip abduction peak torque and lesser gluteus medius activation predicted greater hip internal rotation angle (R2 change = .15; P = .04). No meaningful mediation effects were observed (υadj < .01). In females, after accounting for femoral alignment, less gluteal strength and higher muscle activation were marginally associated with valgus movement. In males, less gluteal strength was associated with a more varus posture. Gluteal strength did not mediate femoral alignment. Future research should determine the capability of females to use their strength efficiently.

A passive back exoskeleton supporting symmetric and asymmetric lifting in stoop and squat posture reduces trunk and hip extensor muscle activity and adjusts body posture – A laboratory study

The influence of a passive exoskeleton was assessed during repetitive lifting with different lifting styles (squat, stoop) and orientations (frontal/symmetric, lateral/asymmetric) on trunk and hip extensor muscle activity (primary outcomes), abdominal, leg, and shoulder muscle activity, joint kinematics, and heart rate (secondary outcomes). Using the exoskeleton significantly and partially clinically relevant reduced median/peak activity of the erector spinae (≤6%), biceps femoris (≤28%), rectus abdominis (≤6%) and increased median/peak activity of the vastus lateralis (≤69%), trapezius descendens (≤19%), and median knee (≤6%) and hip flexion angles (≤11%). Using the exoskeleton had only limited influence on muscular responses. The findings imply the exoskeleton particularly supports hip extension and requires an adjusted body posture during lifting with different styles and orientations. The potential of using exoskeletons for primary/secondary prevention of musculoskeletal disorders should be investigated in future research including a greater diversity of users in terms of age, gender, health status.

Hip and Knee Extensor Activation During the Hip Thrust and Rear-Foot-Elevated Split Squat in Trained Females.

McCurdy, K, Walker, J, Kelly, C, and Polinski, M. Hip and knee extensor activation during the hip thrust and rear-foot-elevated split squat in trained females. J Strength Cond Res 35(5): 1201-1207, 2021-The aim of the study was to compare hip and knee extensor muscle activation between the hip thrust (HT) and rear-foot-elevated split squat (RFESS) within different depths and the entire range of motion. Twenty, young adult female subjects (age, 20.9 ± 1.3 years; height, 164.6 ± 7.5 cm; mass 63.2 ± 8.8 kg) with an intermediate level of resistance training experience completed the study. Three repetitions were completed at 80% of the 1-repetition maximum. Gluteus maximus, vastus lateralis, and the medial (semitendinosus and semimembranosus) and lateral (biceps femoris) hamstrings electromyographic data were compared at the top, middle, and bottom one-third of the hip range of motion and for the entire repetition. A repeated-measures analysis of variance was used to test significance set at p ≤ 0.05. All 4 muscles revealed higher (p < 0.001) activation at the top position of the HT compared with the middle and bottom, whereas higher scores (p < 0.001) were found in the bottom position during the RFESS. The HT revealed greater activity (p < 0.001) than the RFESS in all muscles at the top, whereas the RFESS showed higher scores (p < 0.001) than the HT in all muscles in the bottom position. For the entire repetition, the RFESS produce significantly greater vastus lateralis activation (59.4 vs 43.6%). The data indicate that the greatest effect for the HT is demonstrated in the top position and at the bottom for the RFESS. Thus, we recommend to implement both exercises in a training program to maximize gluteus maximus and hamstring activation across the full range of motion. For the greatest vastus lateralis activation, the RFESS is recommended.

Effect of 4 Weeks of Anti-Gravity Treadmill Training on Isokinetic Muscle Strength and Muscle Activity in Adults Patients with a Femoral Fracture: A Randomized Controlled Trial.

This study aimed to identify the effect of anti-gravity treadmill training on isokinetic lower-limb muscle strength and muscle activities in patients surgically treated for a hip fracture. A total of 34 participants were randomly assigned into two groups: anti-gravity treadmill training group (n = 17) and control group (n = 17). The isokinetic muscle strength and endurance of hip flexor and extensor and the activities of the vastus lateralis (VL), vastus medialis (VM), gluteus maximus (GM), and gluteus medialis (Gm) muscles were measured before and after 4 weeks of the interventions. Significant improvements were observed in isokinetic muscle strength and endurance of hip flexors and extensors in both groups (p < 0.05); however, no significant differences were observed between the groups (p > 0.05) except for muscle strength of the hip extensor (d = 0.78, p = 0029). Statistically significant increases in the muscle activity of VL, VM, GM, and Gm were found before and after the intervention (p < 0.05), and significant differences in muscle activities of GM (d = 2.64, p < 0.001) and Gm (d = 2.59, p < 0.001) were observed between the groups. Our results indicate that both groups showed improvement in muscle strength, endurance, and activities after the intervention. Additionally, anti-gravity treadmill training improved significantly more muscle strength at 60°/s of the hip extensor and gluteus muscle activities than conventional therapy, which may be appropriate for patients with hip fracture surgery.

Different Lower-Limb Setup Positions Do Not Consistently Change Backstroke Start Time to 10 m.

Backstroke starts involve the athlete starting from a flexed position with their feet against the pool wall and then extending their ankles, knees, hips and back to push off; however, swimmers can start in different positions. The purpose of this study was to evaluate the performance impact of different knee extension angles in the setup position for a backstroke start. Ten backstroke swimmers completed maximum-effort starts in each of two setup positions: one with the knees maximally flexed, and one with the knees less flexed. The start handles and touchpad were instrumented with multi-axial force sensors. Activity of major hip and knee extensors was measured using surface electromyography. Body position in the sagittal plane was recorded using high-speed cameras. There was no overall difference in time to 10 m between the two conditions (p = 0.36, dz = 0.12), but some participants showed differences as large as 0.12 s in time to 10 m between start conditions. We observed that starts performed from a setup position with less knee flexion had an average 0.07 m greater head entry distance (p = 0.07, dz = 0.53), while starts from a setup position with maximal knee flexion had an average 0.2 m/s greater takeoff velocity (p = 0.02, dz = 0.78). Both head entry distance and takeoff velocity are related to start performance, suggesting each position may optimize different aspects of the backstroke start. Coaches should assess athletes individually to determine which position is optimal.

Comparison of effects of joint flexibility on the lumbo-pelvic rhythm in healthy university students while bending the trunk forward.

[Purpose] To clarify the influence of flexibilities of the hip and lumbar spine joints on bending the trunk forward. [Participants and Methods] We assessed the joint flexibility of 47 healthy university students using the Beighton hypermobility score and assigned them to the group of normal or poor flexibility. We performed electromyography to acquire kinematic data and analyzed the three-dimensional motion while the students bent their trunks forward. Further, we compared the groups based on angular displacements of the hip joint and lumbar spine in each phase of the movement. Offset of the erector spinae and hip extensor muscle activity was calculated as a percentage (%) of the maximum range of motion. [Results] The lumbo-pelvic rhythm differed between participants with and without poor flexibility of the hip joint in the second half of the forward bending task. Participants with poor flexibility of the hip joint showed activation of the erector spinae and biceps femoris for a longer period compared to those with normal flexibility. Notably, flexion–relaxation responses were not found in the biceps femoris of 30% of the participants. [Conclusion] Poor hip joint flexibility may cause low back pain. Measuring the lumbo-pelvic rhythm might help identify individuals at a high risk of low back pain while they are still healthy.

Influence of Sacroiliac Bracing on Muscle Activation Strategies During 2 Functional Tasks in Standing-Tolerant and Standing-Intolerant Individuals.

People who develop low back pain during standing (standing-intolerant) are a subclinical group at risk for clinical low back pain. Standing-intolerant individuals respond favorably to stabilization exercise and may be similar to people with sacroiliac joint dysfunction that respond to stabilization approaches including sacroiliac joint (SIJ) bracing. The purpose was to characterize muscle activation and response to SIJ bracing in standing-tolerant and standing-intolerant individuals during forward flexion and unilateral stance. Trunk and hip electromyography data were collected from 31 participants (17 standing-tolerant and 14 standing-intolerant) while performing these tasks with and without SIJ bracing. Kinematics were captured concurrently and used for movement phase identification. Cross-correlation quantified trunk coactivation and extensor timing during return-to-stand from forward flexion; root mean square amplitude quantified gluteal activity during unilateral stance. The standing-intolerant group had elevated erector spinae-external oblique coactivation without bracing, and erector spinae-internal oblique coactivation with bracing during return-to-stand compared with standing-tolerant individuals. Both groups reversed extensor sequencing during return-to-stand with bracing. Standing-tolerant individuals had higher hip abductor activity in nondominant unilateral stance and increased hip extensor activity with bracing. SIJ bracing could be a useful adjunct to other interventions targeted toward facilitating appropriate muscle activation in standing-intolerant individuals.

The Myosuit: Bi-articular Anti-gravity Exosuit That Reduces Hip Extensor Activity in Sitting Transfers.

Muscle weakness—which can result from neurological injuries, genetic disorders, or typical aging—can affect a person's mobility and quality of life. For many people with muscle weakness, assistive devices provide the means to regain mobility and independence. These devices range from well-established technology, such as wheelchairs, to newer technologies, such as exoskeletons and exosuits. For assistive devices to be used in everyday life, they must provide assistance across activities of daily living (ADLs) in an unobtrusive manner. This article introduces the Myosuit, a soft, wearable device designed to provide continuous assistance at the hip and knee joint when working with and against gravity in ADLs. This robotic device combines active and passive elements with a closed-loop force controller designed to behave like an external muscle (exomuscle) and deliver gravity compensation to the user. At 4.1 kg (4.6 kg with batteries), the Myosuit is one of the lightest untethered devices capable of delivering gravity support to the user's knee and hip joints. This article presents the design and control principles of the Myosuit. It describes the textile interface, tendon actuators, and a bi-articular, synergy-based approach for continuous assistance. The assistive controller, based on bi-articular force assistance, was tested with a single subject who performed sitting transfers, one of the most gravity-intensive ADLs. The results show that the control concept can successfully identify changes in the posture and assist hip and knee extension with up to 26% of the natural knee moment and up to 35% of the knee power. We conclude that the Myosuit's novel approach to assistance using a bi-articular architecture, in combination with the posture-based force controller, can effectively assist its users in gravity-intensive ADLs, such as sitting transfers.

Flexion Reflex Can Interrupt and Reset the Swimming Rhythm

The spinal cord can generate the hip flexor nerve activity underlying leg withdrawal (flexion reflex) and the rhythmic, alternating hip flexor and extensor activities underlying locomotion and scratching, even in the absence of brain inputs and movement-related sensory feedback. It has been hypothesized that a common set of spinal interneurons mediates flexion reflex and the flexion components of locomotion and scratching. Leg cutaneous stimuli that evoke flexion reflex can alter the timing of (i.e., reset) cat walking and turtle scratching rhythms; in addition, reflex responses to leg cutaneous stimuli can be modified during cat and human walking and turtle scratching. Both of these effects depend on the phase (flexion or extension) of the rhythm in which the stimuli occur. However, similar interactions between leg flexion reflex and swimming have not been reported. We show here that a tap to the foot interrupted and reset the rhythm of forward swimming in spinal, immobilized turtles if the tap occurred during the swim hip extensor phase. In addition, the hip flexor nerve response to an electrical foot stimulus was reduced or eliminated during the swim hip extensor phase. These two phase-dependent effects of flexion reflex on the swim rhythm and vice versa together demonstrate that the flexion reflex spinal circuit shares key components with or has strong interactions with the swimming spinal network, as has been shown previously for cat walking and turtle scratching. Therefore, leg flexion reflex circuits likely share key spinal interneurons with locomotion and scratching networks across limbed vertebrates generally. The spinal cord can generate leg withdrawal (flexion reflex), locomotion, and scratching in limbed vertebrates. It has been hypothesized that there is a common set of spinal cord neurons that produce hip flexion during flexion reflex, locomotion, and scratching based on evidence from studies of cat and human walking and turtle scratching. We show here that flexion reflex and swimming also share key spinal cord components based on evidence from turtles. Foot stimulation can reset the timing of the swimming rhythm and the response to each foot stimulation can itself be altered by the swim rhythm. Collectively, these studies suggest that spinal cord neuronal networks underlying flexion reflex, multiple forms of locomotion, and scratching share key components.

The effects of a passive exoskeleton on muscle activity, discomfort and endurance time in forward bending work

Exoskeletons may form a new strategy to reduce the risk of developing low back pain in stressful jobs. In the present study we examined the potential of a so-called passive exoskeleton on muscle activity, discomfort and endurance time in prolonged forward-bended working postures.Eighteen subjects performed two tasks: a simulated assembly task with the trunk in a forward-bended position and static holding of the same trunk position without further activity. We measured the electromyography for muscles in the back, abdomen and legs. We also measured the perceived local discomfort. In the static holding task we determined the endurance, defined as the time that people could continue without passing a specified discomfort threshold.In the assembly task we found lower muscle activity (by 35–38%) and lower discomfort in the low back when wearing the exoskeleton. Additionally, the hip extensor activity was reduced. The exoskeleton led to more discomfort in the chest region. In the task of static holding, we observed that exoskeleton use led to an increase in endurance time from 3.2 to 9.7 min, on average.The results illustrate the good potential of this passive exoskeleton to reduce the internal muscle forces and (reactive) spinal forces in the lumbar region. However, the adoption of an over-extended knee position might be, among others, one of the concerns when using the exoskeleton.

Changes in the activity of trunk and hip extensor muscles during bridge exercises with variations in unilateral knee joint angle.

[Purpose] This study compared abdominal and hip extensor muscle activity during a bridge exercise with various knee joint angles. [Subjects and Methods] Twenty-two healthy male subjects performed a bridge exercise in which the knee joint angle was altered. While subjects performed the bridge exercise, external oblique, internal oblique, gluteus maximus, and semitendinosus muscle activity was measured using electromyography. [Results] The bilateral external and internal oblique muscle activity was significantly higher at 0° knee flexion compared to 120°, 90°, and 60°. The bilateral gluteus maximus muscle activity was significantly different at 0° of knee flexion compared to 120°, 90°, and 60°. The ipsilateral semitendinosus muscle activity was significantly increased at 90° and 60° of knee flexion compared to 120°, and significantly decreased at 0° knee flexion compared with 120°, 90°, and 60°. The contralateral semitendinosus muscle activity was significantly higher at 60° of knee flexion than at 120°, and significantly higher at 0° of knee flexion than at 120°, 90°, and 60°. [Conclusion] Bridge exercises performed with knee flexion less than 90° may be used to train the ipsilateral semitendinosus. Furthermore, bridge exercise performed with one leg may be used to train abdominal and hip extensor muscles.

Hip kinematics and kinetics in persons with and without cam femoroacetabular impingement during a deep squat task

BackgroundPrevious studies have indicated that hip and pelvis kinematics may be altered during functional tasks in persons with femoroacetabular impingement. The purpose of this study was to compare hip and pelvis kinematics and kinetics during a deep squat task between persons with cam femoroacetabular impingement and pain-free controls. MethodsFifteen persons with cam femoroacetabular impingement and 15 persons without cam femoroacetabular impingement performed a deep squat task. Peak hip flexion, abduction, and internal rotation, and mean hip extensor, adductor, and external rotator moments were quantified. Independent t-tests (α<0.05) were used to evaluate between group differences. FindingsCompared to the control group, persons with cam femoroacetabular impingement demonstrated decreased peak hip internal rotation (15.2° (SD 9.5°) vs. 9.4° (SD 7.8°); P=0.041) and decreased mean hip extensor moments (0.56 (SD 0.12) Nm/kg vs. 0.45 (SD 0.15) Nm/kg; P=0.018). In addition persons in the cam femoroacetabular impingement group demonstrated decreased posterior pelvis tilt during squat descent compared to the control group, resulting in a more anteriorly tilted pelvis at the time peak hip flexion (12.5° (SD 17.1°) vs. 23.0° (SD 12.4°); P=0.024). InterpretationThe decreased hip internal rotation observed in persons with cam femoroacetabular impingement may be the result of bony impingement. Furthermore, the decrease in posterior pelvis tilt may contribute to impingement by further approximating the femoral head–neck junction with the acetabulum. Additionally, decreased hip extensor moments suggest that diminished hip extensor muscle activity may contribute to decreased posterior pelvis tilt.

골반압박벨트 착용에 유무에 따른 동적 균형과제 수행 시 균형과 체간근과 고관절 신전근의 근활성도 비교

The purpose of this study was to investigate the dynamic balance and activity of internal oblique muscle, multifidus muscle, gluteus maximus muscle, biceps femoris muscle during the Y balance test following the wearing of pelvic compression belt. Forty healthy adults were recruited for this test. The dynamic balance score was estimated as the following: (anterior+posteromdial+posterolateral)/( length). The electromyography signals were measured through %reference voluntary contraction, which was normalized by reference voluntary contraction of Y balance test without wearing the pelvic compression belt. The paired t-test was carried out to compare the dynamic balance score and the activity of the trunk and hip extensor with and without the wearing of pelvic compression belt. The dynamic balance score of the Y balance test when wearing pelvic compression belt was significantly than when measured without wearing the pelvic compression belt (p.05). In conclusion, this study shows that the wearing of pelvic compression belt affects trunk muscle and hip extensor muscle activity related to the pelvic mobility and stability and increases dynamic balance and also contributes to the stabilization of the external pelvic stabilization.

Muscle Activation and Onset Times of Hip Extensors during Various Loads of a Closed Kinetic Chain Exercise

The aim of this study was to determine the muscle activity and onset time of hip extensors during a closed kinetic chain exercise (deadlift) at sub-maximal loads of 30%, 40%, 50%, and 75% of one repetition maximum (1RM). Twelve healthy males with at least three years of resistance training experience volunteered for the study. Biceps femoris (BF) and gluteus maximus (GM) muscle activity, onset time, peak and mean power were measured during the concentric phase of the deadlift. There was no main effect (p > 0.05) or no interaction effect for the onset time in BF and GM and for each load BF and GM had similar muscle activity. Increasing the external load during deadlift had no adverse effect on the relative onset time and it did not promote BF onset to occur before GM onset, thus both muscles were simultaneously activated, which should not compromise a delay in GM.