Relationships among lateral medicine ball throw test performance, HIP and trunk muscle strength, and lower limb kinematics: A cross-sectional study.

INTRODUCTION: The lateral medicine ball throw (LMBT) test is used to evaluate the throwing action, involving the entire kinetic chain and the principle of force transfer, with association between the strength of the lower limb and trunk muscles and the lower limb kinematics. The LMBT to investigate the association between lower limb kinematics and hip and trunk muscle strength. EXPERIMENTAL: This was a cross-sectional study with 84 healthy and physically active young people. Determinations were made of the maximum isometric strengths of the hip abductor, lateral rotator, extensor, and flexor muscles, and the trunk lateral flexors and extensors. Kinematic analyses (2D) of the hip, knee, and ankle in the sagittal and frontal planes were performed during the countermovement phase of the LMBT, together with quantification of LMBT. Statistical analysis of the associations employed multiple linear regression, with α = 5%. RESULTS: There were significant associations between the LMBT and the independent variables hip extensors strength, trunk flexors strength, valgus angle, and knee flexion angle and gender. The regression model presented adjusted R2 = 0.622. CONCLUSIONS: LMBT was influenced by the trunk flexor and hip extensor muscle strengths, knee flexion kinematics, lower limb valgus in the countermovement phase, and gender.

Ankle dorsiflexion range of motion and hip abductor strength can predict Lower Quarter Y-Balance Test performance in healthy males.

OBJECTIVES: The aim of the study was to assess whether strength and range of motion (ROM) of the hip and ankle are the factors determining performance in the Lower Quarter Y-Balance test (YBT-LQ). DESIGN: Cross-sectional study. PARTICIPANTS: 66 healthy males (age: 25.2±6.8 years) participated in this study. MAIN OUTCOME MEASURES: Participants underwent assessments of ankle dorsiflexion (DF) ROM, hip internal rotation (IR) ROM, external rotation (ER) ROM and isometric strength of hip abductor (ABD), extensor (EXT) and external rotators (ERS) muscles together with YBT-LQ for both legs. A forward 2-steps multiple linear regression analysis was conducted to examine the relationship between the predictor variables and the criterion variable. RESULTS: Ankle DF ROM predicted anterior (ANT) reach (R2 = 0.49; R2 = 0.33; p < 0.001). The model with hip ABD strength and ankle DF ROM explained posteromedial (PM) reach variance for stance leg (R2 = 0.35; p < 0.001), while only hip ABD strength was included for kicking leg (R2 = 0.19; p = 0.007). The model with ankle DF ROM and hip ABD strength explained posterolateral (PL) reach for stance leg (R2 = 0.41; p < 0.001). Hip ABD was the only predictor for kicking leg PL reach (R2 = 0.15; p < 0.001). YBT-LQ composite score was explained by ankle DF ROM and hip ABD strength for both legs (R2 = 0.44; p < 0.001) and (R2 = 0.25; p = 0.002). CONCLUSION: Hip ABD strength and ankle DF ROM can determine performance in the YBT-LQ. Strength of hip EXT, ERS as well as ROM of hip IR and ER did not predict YBT-LQ performance.

Effects of static exercises on hip muscle fatigue and knee wobble assessed by surface electromyography and inertial measurement unit data.

Hip muscle weakness can be a precursor to or a result of lower limb injuries. Assessment of hip muscle strength and muscle motor fatigue in the clinic is important for diagnosing and treating hip-related impairments. Muscle motor fatigue can be assessed with surface electromyography (sEMG), however sEMG requires specialized equipment and training. Inertial measurement units (IMUs) are wearable devices used to measure human motion, yet it remains unclear if they can be used as a low-cost alternative method to measure hip muscle fatigue. The goals of this work were to (1) identify which of five pre-selected exercises most consistently and effectively elicited muscle fatigue in the gluteus maximus, gluteus medius, and rectus femoris muscles and (2) determine the relationship between muscle fatigue using sEMG sensors and knee wobble using an IMU device. This work suggests that a wall sit and single leg knee raise activity fatigue the gluteus medius, gluteus maximus, and rectus femoris muscles most reliably (p < 0.05) and that the gluteus medius and gluteus maximus muscles were fatigued to a greater extent than the rectus femoris (p = 0.031 and p = 0.0023, respectively). Additionally, while acceleration data from a single IMU placed on the knee suggested that more knee wobble may be an indicator of muscle fatigue, this single IMU is not capable of reliably assessing fatigue level. These results suggest the wall sit activity could be used as simple, static exercise to elicit hip muscle fatigue in the clinic, and that assessment of knee wobble in addition to other IMU measures could potentially be used to infer muscle fatigue under controlled conditions. Future work examining the relationship between IMU data, muscle fatigue, and multi-limb dynamics should be explored to develop an accessible, low-cost, fast and standardized method to measure fatiguability of the hip muscles in the clinic.

Voluntary Contraction of the Abdominal Muscles Increases Hip Muscle Activation During Lower-Extremity Exercises: A Critically Appraised Topic.

CLINICAL SCENARIO: Existing studies have posited that incorporating abdominal enhancement techniques during lower-extremity exercises might mitigate compensatory pelvic motions and enhance the engagement of specific hip muscles. CLINICAL QUESTION: Does performing lower-extremity exercises with abdominal enhancement techniques increase hip muscle activation levels in healthy individuals? Summary of Key Finding: After the literature review, 4 cross-sectional studies met the inclusion criteria and were included in this critically appraised topic. CLINICAL BOTTOM LINE: There is moderate evidence to support that prone hip extension with abdominal enhancement may increase gluteus maximus and hamstring muscle activity. Gluteus medius activity may not be affected by abdominal enhancement during hip abduction exercises. Strength and Recommendation: The collective findings from the 4 cross-sectional trials indicate that the incorporation of abdominal enhancement techniques during lower-extremity exercises may have the potential to enhance targeted muscle activation levels in healthy individuals. Further research is recommended to establish more robust conclusions.

Increasing cadence with a metronome and running barefoot changes the sagittal kinematics of the lower limbs and trunk.

The purpose was to compare two non-laboratory based running retraining programs on lower limb and trunk kinematics in recreational runners. Seventy recreational runners (30 ± 7.3 years old, 40% female) were randomised to a barefoot running group (BAR), a group wearing a digital metronome with their basal cadence increased by 10% (CAD), and a control group (CON). BAR and CAD groups included intervals from 15 to 40 min over 10 weeks and 3 days/week. 3D sagittal kinematics of the ankle, knee, hip, pelvis, and trunk were measured before and after the retraining program, at comfortable and high speeds. A 3 × 2 mixed ANOVA revealed that BAR and CAD groups increased knee and hip flexion at footstrike, increased peak hip flexion during stance and flight phase, decreased peak hip extension during flight phase, and increased anterior pelvic tilt at both speeds after retraining. In addition, BAR increased ankle plantar flexion at footstrike and increased anterior trunk tilt. Both retraining programs demonstrated significant moderate to large effect size changes in parameters that could reduce the mechanical risks of injury associated with excessive knee stress, which is of interest to coaches, runners and those prescribing rehabilitation and injury prevention programs.

Golfers' Performance Is Improved More by Combining Foam Rolling and Dynamic Stretch to the Lead Hip Than Practice Golf Swinging.

ABSTRACT: Hamada, Y, Akasaka, K, Otsudo, T, Sawada, Y, Hattori, H, Kikuchi, Y, and Hall, T. Golfers' performance is improved more by combining foam rolling and dynamic stretch to the lead hip than practice golf swinging. J Strength Cond Res 38(7): e391-e397, 2024-Warming up is considered effective in improving performance and preventing injury. Despite this, there have been few studies investigating warm-up programs in golf and whether specific factors contribute to improved performance. The purpose of this study was to examine the immediate effects of combined foam rolling and dynamic stretch (FR + DS) to the lead hip on golf swing performance, hip range of motion (ROM), and muscle strength in amateur golfers using a randomized crossover design. The study sample comprised 22 men (mean ± SD ; age, 32.6 ± 8.5 years, body mass index (BMI), 23.4 ± 2.7 kg·m -2 ). Subjects were assigned to receive either FR + DS or repetitive golf swing practice (SW) before crossing over to the other intervention for another day. Measurements included golf swing performance (ball speed, club head speed, flight distance ["carry"], spin rate, and launch angle), hip internal rotation (IR), and external rotation (ER) ROM, as well as hip IR and ER muscle strength. Comparisons between groups were made before and after each intervention. For golf swing performance, FR + DS improved "carry" significantly more than SW ( p < 0.05). No significant differences in golf swing performance other than "carry" were found. In addition, IR ROM and IR muscle strength of the lead hip were significantly increased in the FR + DS group ( p < 0.05). FR + DS has effects on improving lead hip IR ROM and IR muscle strength, which may facilitate golfers' swing and "carry." FR + DS shows promise as a warm-up method for amateur golfers who want to improve golf performance.

The effect of marathon running on the lower extremity kinematics and muscle activities during walking and running tasks.

Patellofemoral pain syndrome (PFPS) is a common injury among runners, and it is thought that abnormal lower extremity biomechanics contribute to its development. However, the relationship between biomechanical changes after a marathon and PFPS injury remains limited. This study aims to investigate whether differences in knee and hip kinematics and lower extremity muscle activities exist in recreational runners before and after a marathon. Additionally, it aims to explore the relationship between these biomechanical changes and the development of PFPS injury. 12 recreational runners participated in the study. Kinematics and muscle activities of the lower extremity were recorded during walking (5 km/h) and running (10 km/h) tasks within 24 hours before and within 5 hours after a marathon. After the marathon, there was a significant decrease in peak knee flexion (walking: p = 0.006; running: p = 0.006) and an increase in peak hip internal rotation (walking: p = 0.026; running: p = 0.015) during the stance phase of both walking and running compared to before the marathon. The study demonstrates a decrease in knee flexion and an increase in hip internal rotation during the stance phase of gait tasks after completing a marathon, which may increase the risk of developing PFPS injury.

Decreased moment of inertia of the lower limb facilitates a rapid hip internal rotation in a simulated foot impact maneuver. A laboratory-controlled biomechanical study for a precursor mechanism of noncontact anterior cruciate ligament injury.

BACKGROUND: Anterior cruciate ligament injury frequently occurs in the deceleration with the knee-extended position. In addition, a rapid hip internal rotation is concomitantly observed. However, how the extended knee position induces the hip internal rotation is unclear. METHODS: Sixteen healthy participants performed the simulated foot impact task on the experimental chair. To vary the knee flexion angle, the following four-foot placement positions relative to the pelvis segment, i.e.: 1) near; 2) middle; 3) far; and 4) far + heel strike, were tested. The reflective marker positions and the ground reaction force (GRF) data were collected. The moment of inertia of the entire lower limb around its long axis as well as the peak hip internal rotation angular velocity were calculated and compared among four conditions (Wilcoxon Signed-Rank Test with Bonferroni correction, P<0.0083). RESULTS: As the knee extended from the near to far + heel strike condition, the moment of inertia of the entire lower limb significantly decreased and hip internal rotation angular velocity significantly increased (P<0.001). CONCLUSIONS: The extended knee position with far foot placement from torso reduces the inertial resistance of the entire lower limb around its long axis and is vulnerable to the hip internal rotation.

Effect of unpredictable timing on the hip, knee, and ankle kinematics and center of mass during deceleration tasks.

BACKGROUND: Unpredictable stopping or deceleration tasks are crucial to prevent ACL injury. The purpose of this study was to reveal differences and relationships in kinematics during different deceleration tasks with and without anticipation. METHODS: Twenty-four collegiate athletes were recruited. Three commercial video cameras were used to capture frontal and sagittal lower-extremity kinematics. Participants were instructed to perform three deceleration tasks: 1) anticipated stopping and running backward at a point indicated previously (SRB-P); 2) anticipated stopping and running backward in front of a badminton net (SRB-N); and 3) unanticipated stopping and running backward upon random flashing of a light (SRB-U). Differences and relationships between hip, knee, and ankle kinematics at stopping (SS) and deceleration steps (DS) and the height of the great trochanter (HGT) at SS were analyzed. RESULTS: For all tasks, the knee flexion angle was less than 25° at SS. There were no significant differences in hip, knee, and ankle kinematics between tasks. HGT during SRB-U was higher than that in the other tasks at DS. Hip flexion angle at SS and DS was significantly correlated with HGT at SS. During SRB_P and SRB_N, only knee flexion angle at DS was significantly correlated with HGT at SS. CONCLUSIONS: The deceleration task in this study, SRB, causes a low knee-flexion angle at SS. The COM remained higher during unanticipated stopping, which is related only to hip flexion angle during the task. Knee flexion movement does not contribute to lowering COM during an unpredictable deceleration task.

Lower Extremity Kinematic and Kinetic Characteristics as Effects on Running Economy of Recreational Runners.

PURPOSE: This study aimed to determine associations between running economy (RE) and running sagittal plane kinematic and kinetic parameters. METHOD: A total of 30 male recreational runners (age: 21.21 ± 1.22 yr, V̇O 2max : 54.61 ± 5.42 mL·kg -1 ·min -1 ) participated in two separate test sessions. In the first session, the participant's body composition and RE at 10 and 12 km·h -1 were measured. In the second session, measurements were taken for the sagittal plane of hip, knee, and ankle angles and range of motion (ROM), as well as ground reaction force. RESULTS: Moderate correlations were found between lower energy costs at 12 km·h -1 and smaller hip flexion at toe-off ( r = 0.373) as well as smaller peak hip flexion during stance ( r = 0.397). During the swing phase, lower energy costs at 10 km·h -1 were moderately correlated with smaller peak knee flexion and smaller knee flexion and extension ROM ( r = 0.366-0.443). Lower energy costs at 12 km·h -1 were moderately correlated with smaller peak hip and knee flexion as well as knee extension ROM ( r = 0.369-0.427). In terms of kinetics, there was a moderate correlation between higher energy costs at 10 km·h -1 and larger peak active force, as well as larger peak braking and propulsion force ( r = -0.470-0.488). Lower energy costs at 12 km·h -1 were moderately to largely correlated with smaller peak impact and braking force ( r = 0.486 and -0.500, respectively). Regarding the statistical parametric mapping analysis, most outcomes showed associations with RE at 10 km·h -1 , including knee flexion (42.5%-65.5% of the gait cycle), ankle plantarflexion (32.5%-36% of the gait cycle), active force (30.5%-35% of the stance phase), and propulsion force (68%-72.5% of the stance phase). Lower energy costs at 12 km·h -1 were correlated with smaller hip flexion (5.5%-12% and 66.5%-74%) and smaller knee flexion (57%-57.5%) during the running gait cycle. CONCLUSIONS: This study indicates that biomechanical factors are associated with RE in recreational runners. To design effective training methods to improve RE, coaches and runners should focus on the sagittal plane kinematics of the hip, knee, and ankle, as well as lower vertical and horizontal kinetic parameters.

Concentric and eccentric hip musculotendon work depends on backpack loads and walking slopes.

Hip muscle weakness is associated with low back and leg injuries. In addition, hiking with heavy loads is linked to high incidence of overuse injuries. Walking with heavy loads on slopes alters hip biomechanics compared to unloaded walking, but individual muscle mechanical work in these challenging conditions is unknown. Using movement simulations, we quantified hip muscle concentric and eccentric work during walking on 0° and ±10° slopes with, and without 40% bodyweight added loads, and with and without a hip belt. For gluteus maximus, psoas, iliacus, gluteus medius, and biceps femoris long head, both concentric and eccentric work were greatest during uphill walking. For rectus femoris and semimembranosus, concentric work was greatest during uphill and eccentric work was greatest during downhill walking. Loaded walking had greater concentric and eccentric work from rectus femoris, biceps femoris long head, and gluteus maximus. Psoas concentric work was greatest while carrying loads regardless of hip belt usage, but eccentric work was only greater than unloaded walking when using a hip belt. Loaded and uphill walking had high concentric work from gluteus maximus, and high eccentric work from gluteus medius and biceps femoris long head. Carrying heavy loads uphill may lead to excessive hip muscle fatigue and heightened injury risk. Effects of the greater eccentric work from hip flexors when wearing a hip belt on lumbar spine forces and pelvic stability should be investigated. Military and other occupational groups who carry heavy backpacks with hip belts should maintain eccentric strength of hip flexors and hamstrings.

Effect of Exhaustive Exercise on Lumbopelvic-Hip Complex Stability, Muscle Activity, and Movement Patterns.

This study aimed to evaluate the effect of exhaustive exercise on lumbopelvic-hip complex (LPHC) muscle activity, stability, and single-leg squat kinematics. Twenty-two healthy participants (12 females, 23.5 ± 3.1 years) were recruited. LPHC stability was measured by number of errors committed during a seated trunk control test (STCT). Surface electromyography recorded muscle activity of rectus abdominis (RA), external oblique, internal oblique (IO), erector spinae, and gluteus medius during the STCT and single-leg squat, and was normalized to peak activity during the task. Two-dimensional motion analysis quantified frontal and sagittal plane kinematics of the trunk, hip, and knee. Following exhaustive exercise, STCT performance worsened (number of errors: pre: 5.5 (interquartile range (IQR) = 1.4-9.0), post: 8.0 (IQR = 3.6-11.3), p = 0.026.), RA activity increased during the single-leg squat (pre: 42.1 (IQR = 33.6-48.5)%, post: 61.1 (IQR = 39.4-156.7 %, p =.004), and participants displayed less hip and knee flexion (hip: pre: 72.4 ± 22.1°; post: 66.2 ± 22.5°, p =.049; knee: pre: 72.4 ± 15.4°; post: 67.4 ± 18.2°, p =.005). Full-body exhaustive exercise negatively affected isolated LPHC stability and resulted in greater RA activity during the single-leg squat. Hip and knee flexion decreased during a single-leg squat after exhaustive exercise which could indicate decreased athletic performance, but changes in the quality of movement during other tasks should be further investigated.

Real-Time-Capable Muscle Force Estimation for Monitoring Robotic Rehabilitation Therapy in the Intensive Care Unit.

In this paper, a method is proposed to enable real-time monitoring of muscle forces during robotic rehabilitation therapy in the ICU. This method is solely based on sensor information provided by the rehabilitation robot. In current clinical practice, monitoring primarily takes place in the later stages of rehabilitation, but it would also be highly beneficial during early stages. Musculoskeletal models have large, mostly unrealized potential to support and improve patient monitoring. The method presented in this paper is based on a state-of-the-art muscle-tendon path model, which is applied to the use case of the robotic rehabilitation device VEMOTION. The muscle force estimation is validated against surface electromyography measurements of lower limb muscles from 12 healthy volunteers The results show an overall correlation of R = 0.70 0.25 for the single-joint muscle m. iliopsoas, which has a ±major contribution to hip flexion. Given this correlation, the proposed model could be used for real-time monitoring of active patient participation.

Relationship between the Hip Abductor Muscles and Abduction Strength in Patients with Hip Osteoarthritis.

This study aimed to determine which muscle the gluteus maximus, gluteus medius, gluteus minimus (Gmin), or tensor fasciae latae (TFL) contributes most to hip abduction strength and to identify effective sites for cross-sectional area (CSA) Gmin and TFL measurement in hip osteoarthritis (OAhip) patients. Twenty-eight patients with OAhip were included. The muscle CSA and volume were determined using magnetic resonance imaging. Peak isometric strength was determined using hand-held dynamometry. Muscle volumes were normalized to the total muscle volume of hip abductors. Multiple regression analysis was performed. The difference between the CSA of Gmin and TFL was calculated, and correlations with volume and muscle strength were determined. Gmin volume was related to abductor muscle strength (p=0.042). The peak CSA of the Gmin correlated with muscle volume and strength. The CSA of the TFL correlated with volume, with no difference between the CSA of the most protruding part of the lesser trochanter and peak CSA. Gmin volume was strongly related to abductor muscle strength. Peak CSA is a useful parameter for assessing the CSA of the Gmin among patients with OAhip. The CSA of the TFL should be measured at the most protruding part of the lesser trochanter.

Individual Muscle Contributions to the Acceleration of the Center of Mass During the Barbell Back Squat in Trained Female Subjects.

ABSTRACT: Goodman, WW, Helms, E, and Graham, DF. Individual muscle contributions to the acceleration of the center of mass during the barbell back squat in trained female subjects. J Strength Cond Res 37(10): 1947-1954, 2023-The squat is used to enhance performance and rehabilitate the lower body. However, muscle forces and how muscles accelerate the center of mass (CoM) are not well understood. The purpose was to determine how lower extremity muscles contribute to the vertical acceleration of the CoM when squatting to parallel using 85% one-repetition maximum. Thirteen female subjects performed squats in a randomized fashion. Musculoskeletal modeling was used to obtain muscle forces and muscle-induced accelerations. The vasti, soleus, and gluteus maximus generated the largest upward accelerations of the CoM, whereas the muscles that produced the largest downward acceleration about the CoM were the hamstrings, iliopsoas, adductors, and tibialis anterior. Our findings indicate that a muscle's function is task and posture specific. That is, muscle function depends on both joint position and how an individual is interacting with the environment.

Effects of Running-induced Fatigue on the Trunk-pelvis-hip Coordination Variability During Treadmill Running at Different Speeds.

OBJECTIVE: The objective of this study was to examine the effects of fatigue on the coordination variability between the trunk, pelvis, and hips during treadmill running. METHODS: The kinematics data were recorded during ten successive treadmill steps running at the preferred speed and at 80% and 120% of the preferred speed. The angle segment data obtained during the running cycles were normalized to 100 data points, and they were split into ten periods. The coordination variability was calculated using the continuous relative phase (CRP) and variability (VCRP) methods for the trunk, pelvic and hip segments before and after the fatigue protocol. RESULTS: The repeated measures analysis of variance showed significant differences in the trunk-pelvic and trunk-hip CRPs and in the CRP variability during the last 30% of the treadmill running cycles after fatigue (p≤0.05). In addition, significant differences were observed in the pelvic-hip CRP and the CRP variability in 40% of the initial treadmill running cycles after fatigue (p≤0.05). CONCLUSION: According to the results of this study, fatigue reduces coordination and increases variability. The central nervous system probably exerts more control on the distal segments for maintaining moving patterns in fatigue conditions.

Effects of gender and fatigue on strength and activity of gluteus medius muscle during a controlled cutting maneuver in preadolescent athletes.

The present study aimed to investigate the effects of gender on hip muscle strength and activity during a controlled cutting maneuver in preadolescent athletes. Fifty-six football and handball preadolescent players participated (35 females and 21 males). Normalized mean activity of the gluteus medius (GM) muscle was measured using surface electromyography during cutting maneuvers in pre-activation and eccentric phases. The stance duration and the strength of hip abductors and external rotators were recorded with a force plate and a handheld dynamometer, respectively. Descriptive statistics and mixed model analysis were used to assess statistical difference (α = 0.05). The results showed that boys activate the GM muscle significantly more than girls during the pre-activation phase (P = 0.022). Boys also demonstrated greater normalized strength of hip external rotation than girls (P = 0.038), but not for hip abduction or duration of stance (P > 0.05). When adjusted for abduction strength, however, boys had significantly shorter stance duration than girls (P = 0.006). It seems that sex-dependent differences are present in preadolescent athletes as observed in the strength of hip external rotator muscles and neuromuscular activity of the GM muscle during a cutting maneuver. Future studies are needed to investigate whether these changes influence risk of lower limb/ACL injury during sport activities.

After scaling to body size hip strength of the residual limb exceeds that of the intact limb among unilateral lower limb prosthesis users.

BACKGROUND: Hip muscles play a prominent role in compensating for the loss of ankle and/or knee muscle function after lower limb amputation. Despite contributions to walking and balance, there is no consensus regarding hip strength deficits in lower limb prosthesis (LLP) users. Identifying patterns of hip muscle weakness in LLP users may increase the specificity of physical therapy interventions (i.e., which muscle group(s) to target), and expedite the search for modifiable factors associated with deficits in hip muscle function among LLP users. The purpose of this study was to test whether hip strength, estimated by maximum voluntary isometric peak torque, differed between the residual and intact limbs of LLP users, and age- and gender-matched controls. METHODS: Twenty-eight LLP users (14 transtibial, 14 transfemoral, 7 dysvascular, 13.5 years since amputation), and 28 age- and gender-matched controls participated in a cross-sectional study. Maximum voluntary isometric hip extension, flexion, abduction, and adduction torque were measured with a motorized dynamometer. Participants completed 15 five-second trials with 10-s rest between trials. Peak isometric hip torque was normalized to body mass × thigh length. A 2-way mixed-ANOVA with a between-subject factor of leg (intact, residual, control) and a within-subject factor of muscle group (extensors, flexors, abductors, adductors) tested for differences in strength among combinations of leg and muscle group (α = 0.05). Multiple comparisons were adjusted using Tukey's Honest-Difference. RESULTS: A significant 2-way interaction between leg and muscle group indicated normalized peak torque differed among combinations of muscle group and leg (p < 0.001). A significant simple main effect of leg (p = 0.001) indicated peak torque differed between two or more legs per muscle group. Post-hoc comparisons revealed hip extensor, flexor, and abductor peak torque was not significantly different between the residual and control legs (p ≥ 0.067) but torques in both legs were significantly greater than in the intact leg (p < 0.001). Peak hip abductor torque was significantly greater in the control and residual legs than the intact leg (p < 0.001), and significantly greater in the residual than control leg (p < 0.001). CONCLUSIONS: Our results suggest that it is the intact, rather than the residual limb, that is weaker. These findings may be due to methodological choices (e.g., normalization), or biomechanical demands placed on residual limb hip muscles. Further research is warranted to both confirm, expand upon, and elucidate possible mechanisms for the present findings; and clarify contributions of intact and residual limb hip muscles to walking and balance in LLP users. CLINICAL TRIAL REGISTRATION: N/A.

Dynamometric Strength Profile of Hip Muscles in Youth Soccer Players.

BACKGROUND: Soccer is the most widely practiced sport in the world, demanding high-speed activities such as jumps, sprints and changes of direction. Therefore, having optimal levels of muscle strength improves performance and reduces the injury rate. OBJECTIVES: The objectives of our study were (i) to determine the dynamometric profile of hip muscle strength in young soccer players by position, evaluated at different isokinetic speeds, (ii) to describe the conventional and functional unilateral muscle strength ratios, (iii) to analyze the bilateral balance. METHODS: Thirty-seven male soccer players (age 17.02 ± 0.92 years) participated in the study. Strength assessment was performed with a functional electromechanical dynamometer, and concentric and eccentric strength of abductors, adductors, extensors and hip flexors were measured bilaterally at 0.5 m/s and 1 m/s. RESULTS: For eccentric right hip abduction at 0.5 m/s, defenders are significantly stronger than midfielders (p = 0.013) and stronger than forwards (p = 0.140). For eccentric right hip adduction at 0.5 m/s, defenders are significantly stronger than midfielders (p = 0.005) and stronger than forwards (p = 0.253), as for eccentric right hip adduction at 1 m/s, defenders are significantly stronger than midfielders (p = 0.014) and stronger than forwards (p = 0.084). There is a significant effect for the conventional strength ratio of left abduction/adduction at 1 m/s. The conventional strength ratio of forwards is significantly higher than that of defenders (p = 0.045) and higher than that of midfielders (p = 0.152). CONCLUSIONS: Concentric and eccentric hip strength values differ according to playing position.