Comparative Effects of 4 Single-Leg Squat Exercises in Subjects With Gluteus Medius Weakness.

CONTEXT: Of the weight-bearing exercises, single-leg squats (SLSs) represent one of the most commonly used hip-strengthening exercises that require more gluteus medius (GMED) activity. To date, no studies have investigated how the 4 SLS exercises affect muscle imbalance of GMED, tensor fasciae latae (TFL), and adductor longus (AL), and kinematics of hip. OBJECTIVE: To investigate the hip muscle activities, onset time, and kinematics during 4 different SLS exercises (unilateral squat, unilateral wall-squat [UWS], lateral step-down, and front step-down) in subjects with GMED weakness. DESIGN: Repeated-measures experimental design. SETTING: Research laboratory. PARTICIPANTS: Twenty-two subjects (11 males and 11 females) participated in this study and were compared using 1-way repeated-measures analysis of variance. MAIN OUTCOME MEASURES: Surface electromyography was used to measure the muscle activities and onset time of the GMED, TFL, and AL, and 3-dimensional motion tracking system was used to measure the hip adduction and internal/external rotation angles during SLS exercises. One-way repeated-measures analysis of variance was used at a significance level of P < .05. RESULTS: The UWS produced higher GMED/TFL activity ratio and lower GMED/TFL onset time ratio than in the other 3 exercises (P < .05). No difference in GMED/AL activity ratio and GMED/AL onset time ratio was observed. The hip adduction angle was greater in UWS than in the other 3 exercises (P < .05). As for the hip internal/external rotation, lateral step-down exhibited higher hip internal rotation angle than front step-down (P < .05). CONCLUSION: The UWS may be recommended as an effective exercise for the subjects with GMED weakness, but they should take care to avoid excessive hip adduction during the exercise.

Effects of footrest heights on muscle fatigue, kinematics, and kinetics during prolonged standing work.

BACKGROUND: Among the tools for relieving lower back pain, footrests are commonly recommended. Few studies have investigated the effects of footrest and the proper application of footrest height. OBJECTIVE: The purpose of this study was to compare the effects of the normalized footrest height on muscle fatigue, kinematics, kinetics, and pain intensity. METHODS: In total, 13 males who had a history of non-specific lower back pain during prolonged standing were recruited. The experimental conditions were 2-hour prolonged standing with no footrest and with footrests of 5%, 10%, and 15% of body height. Muscle fatigue was investigated through measurements of the median frequency ratio and the muscle activity ratio (post/pre) in lumbar erector spinae. The lumbo-pelvic angles, and the external moment in the lumbar region were investigated. A visual analog scale was used to investigate the intensity of the pain. RESULTS: The footrests at 10% and 15% of the body height caused a lower change in the median frequency ratio and the muscle activity ratio than the other conditions. The footrest at 10% of the body height placed the lowest external moment on the lumbar region among all the conditions. The pain intensity was significantly lower in with footrest conditions than with no footrest condition. CONCLUSIONS: The results suggests that a footrest height of 10% of the body height can be recommended as a normalized height for prolonged standing work in subjects with a history of non-specific lower back pain during prolonged standing.