Electromyographic and co-activation patterns during landings: A sex-based analysis in athletes.

Knee injuries remain prevalent in sports involving landing tasks, particularly among non-professional athletes. Sex-specific neuromuscular strategies during landing may contribute to different joint stabilization patterns. The aim of this study was to examine sex-related differences in thigh muscle activation and hamstrings-to-quadriceps (H/Q) co-activation during standardized single-leg landings in recreational athletes. A total of 162 physically active participants (25% women) performed a single-leg drop landing from 30 cm. Surface electromyography was recorded from the rectus femoris and biceps femoris and normalized to maximal voluntary contraction (MVC). Muscle activation was analyzed across early post-contact time windows (50, 100, 150, and 200 ms). Between-sex comparisons were conducted using independent t-tests with Bonferroni correction (α = 0.0033). At the group level, quadriceps activation exceeded hamstrings under MVC-normalized conditions, whereas during the early post-contact phase hamstring activation was slightly higher, with H/Q ratios close to unity. Men showed greater quadriceps activation than women at 50 ms post-contact, which remained significant after correction. Other sex differences did not reach the adjusted significance threshold. No significant sex differences were observed for hamstring activation. Recreational single-leg landings are characterized by high early-phase thigh activation with balanced H/Q ratios. These findings suggest that early neuromuscular responses and sex-specific activation patterns should be considered when designing injury prevention and neuromuscular training programs, particularly those targeting rapid muscle coordination during the initial phase of landing.