Sex differences in climbing endurance emerge from combined physiological adaptation and neural strategies

Background: Sport climbing imposes high endurance demands on finger flexor muscles, which sustain near-isometric loads for prolonged periods. Although women often demonstrate greater muscle endurance than men, the neuromuscular mechanisms underlying potential sex differences in climbing remain unclear. Purpose: Determine whether sex differences in climbing endurance are explained by physiological muscle adaptations, neural strategies of motor unit (MU) control, or both. Methods: High-density surface electromyograms (HD-sEMG) were recorded from the dominant forearm of 9 female and 13 male intermediate climbers during sustained body suspension on a campus board until failure, using two grip depths (20 and 30 mm) to manipulate task demand. EMGs were decomposed into MU discharge trains. Physiological adaptation was assessed via temporal changes in MU action potential amplitude and median frequency (MDF), while neural strategies were evaluated using traditional MU discharge metrics and a mode-based analysis of MU firing patterns. Results: Despite anthropometric differences, time to failure did not differ between sexes. MDF declined more slowly in women, indicating greater resistance to muscle fatigue. Traditional MU metrics showed greater discharge variability and intermittency in women. Mode analysis revealed three common temporal MU firing modes across sexes; however, men exhibited greater reliance on sustained early-phase MU activation, particularly under higher task demands. Conclusion: Sex differences in climbing endurance are not reflected in outcomes alone but arise from distinct neuromuscular mechanisms. Greater physiological fatigue resistance in women is complemented by sex-specific neural strategies of MU rate coding, underscoring the importance of integrating physiological and neural analyses when examining endurance performance in climbing.