Background: Choosing to perform squats on an unstable surface potentially offers advantages surpassing those of their stable counterpart. Objectives: The purpose of this study was to compare muscle activation during squats on stable and unstable surfaces and investigate the relationship among thigh muscles. Design: Observational study. Methods: Nineteen adults participated in this study. The stable surface consisted of a flat floor. The unstable surface involved the use of an air cushion. An air cushion was positioned beneath each foot of the study participants. Surface electromyography was employed to measure muscle activation. %MVC was calculated by measuring muscle activation during squat execution and manual muscle testing. Results: The comparison of muscle activation during squats between stable and unstable surfaces revealed a significant difference in the rectus femoris and biceps femoris (P<.05). On stable surfaces, positive correlations were observed in the rectus femoris, vastus lateralis, and vastus medialis (P<.05). On unstable surfaces, positive correlations were found between the rectus femoris and vastus medialis (P<.05). Conclusion: This study observed an increase in muscle activation of the rectus femoris and biceps femoris during squats on an unstable support surface compared to a stable support surface.

Background: Some patients may not fully recover their daily activity capabilities even after the total hip replacement (THR), and may continue to experience functional limitations for up to a year after the procedure, according to reports. Objectives: The purpose of this study was to examine the effects of machine squat on muscle strength, balance and gait in patients after THR. Design: A randomized controlled trial. Methods: Thirty-three patients after THR were randomly allocated into slide (n=11), reformer (n=11), and control groups (n=11). Each group underwent their respective squat regimens for thirty minutes, seven times a week, for two weeks. Muscle strength changes were assessed using the manual muscle test (MMT), balance was evaluated using the Berg Balance Scale (BBS), and gait analysis was performed using the 10-meter walk test (10MWT). Results: Significant changes in hip flexor and abductor strength were observed in the slide and reformer groups within each group (P<.05). The reformer group showed significant changes in hip extensor strength (P<.05). Significant improvements in BBS were observed in all three groups (P<.05). There were significant changes in 10MWT in the slide and reformer groups (P<.05). A significant difference in hip extensor strength was found between the reformer and control groups after the intervention (P<.0167). Significant differences in BBS were observed between the slide and reformer groups and between the reformer and control groups after the intervention (P<.0167). Conclusion: Our findings suggest that machine squat regimens can be effective for early rehabilitation after THR, improving muscle strength, balance, and gait.