Reactive Strength Index and Inter-Limb Asymmetry in Elite Female Volleyball Players: Insights from Wearable IMU-Based Assessments

Background The Reactive Strength Index (RSI) and inter-limb asymmetry are critical indicators of neuromuscular performance, injury risk, and athletic readiness. While these parameters have been widely examined in laboratory settings, evidence from wearable inertial measurement units (IMUs) in elite female volleyball players remains limited. Methods Twenty elite female volleyball players from the Turkish Women’s Super League participated. Athletes performed countermovement jumps (CMJ), drop jumps (DJ, 30 cm), and single-leg CMJs with bilateral ankle- and waist-mounted WIMU Pro IMUs (100 Hz). Variables analyzed included CMJ height, contact time, RSI (jump height/contact time), and inter-limb asymmetry (percentage difference between right and left limbs). Statistical analysis included Spearman correlations and position-specific comparisons. Results Nearly half of the players demonstrated more than 10% asymmetry, considered clinically meaningful. A moderate negative correlation was observed between asymmetry and RSI (Spearman r = -0.52, p < 0.05), indicating reduced neuromuscular reactivity with greater asymmetry. Middle blockers exhibited the lowest RSI values, while liberos and setters demonstrated higher RSI, reflecting positional demands. Conclusions Wearable IMU-based assessments provide valid field-based insights into asymmetry and reactive strength among elite female volleyball players. Findings highlight the prevalence of asymmetry greater than 10% and its association with reduced RSI, emphasizing the importance of individualized training and injury-prevention strategies.