Position-specific neuromuscular activation and biomechanical characterization of the snap jump in elite male volleyball players: a comparative study of outside and opposite hitters

Background: This study aimed to explore the biomechanical and neuromuscular differences in spike jumps between Outside Hitters (OH) and Opposite Hitters (OPP) in volleyball. Methods: Twelve male national-level volleyball players (six OHs and six OPPs) performed standardized spike maneuvers aligned with their positional roles. Kinematic data were captured using a Qualisys infrared motion capture system, and muscle activation was assessed using a Delsys wireless surface electromyography (sEMG) system. Results: OPPs demonstrated significantly greater right foot landing angle, inter-foot distance and center of mass projection-related distances, indicating a more forward-oriented posture and longer final step. In contrast, OHs exhibited larger shoulder joint line angle and take-off angle, contributing to higher vertical jump performance. Both groups showed asymmetrical force application—right-leg dominance in the braking phase and left-leg dominance in the propulsion phase. Muscle activation patterns were position-specific: OHs relied more on vastus lateralis and gastrocnemius, while OPPs showed greater semitendinosus contribution during propulsion. Conclusions: These position-specific neuromechanical patterns reflect distinct tactical demands, suggesting the need for tailored strength and conditioning programs to enhance performance and reduce injury risks in elite volleyball players.