Sex-Specific Fatigue and Muscle Activation Responses During Single-Leg Side-Hop and Pelvic Stability Assessments Among Active Young Adults

This study examined fatigue- (within-group) and sex-related (between-group) differences in physical performance and muscle activation during physical assessments. Physically active college students (20 males, 20 females) completed side-hop and pelvic stability tests after a warm-up (T-1) and mobilization exercises (T0) and then following each with five 8 min runs at 70% of individualized peak velocity as the fatiguing protocol (T1–T5). No significant within-group performance differences were observed across tests (T0–T5). However, males completed more hops (p < 0.001) and had shorter ground contacts (p < 0.05) than females in the side-hop test with no significant sex-based stability differences. Electromyography data revealed reduced activation (p < 0.05) in various muscles (gastrocnemius, vastus medialis, biceps femoris, gluteus medius, gluteus maximus, erector spinae, obliquus abdominis) under fatigue (various timepoints between T1–T5) compared to baseline (T-1) across tests. Males displayed greater relative reductions in activation (p < 0.01) from pre-activation to ground contact in the gastrocnemius and biceps femoris during the side-hop test. Females exhibited reduced vastus medialis (p = 0.02) activation during the side-hop test and reduced biceps femoris (p = 0.04) activation during the pelvic stability test than males. Physical performance remained stable under fatigue, with sex-specific muscle recruitment strategies appearing as possible compensatory mechanisms.