Acute Effects of Neuromuscular Electrical Stimulation Priming on Volleyball Spike Performance and Three-Dimensional Kinematics.

Volleyball spiking is a complex explosive skill that requires coordinated force generation and transfer across the upper limbs, trunk, and lower limbs. Neuromuscular electrical stimulation (NMES) has been proposed as a preconditioning strategy for enhancing neuromuscular activation; however, its acute effects on phase-specific volleyball spike kinematics remain unclear. This study investigated the acute effects of NMES priming on spike performance and three-dimensional kinematics in male university volleyball players. Thirty participants were randomly assigned to an NMES conditioning group (n = 15) or a control group (n = 15). All participants completed a baseline spike assessment and a second assessment 72 h later. Immediately before the second assessment, the NMES group received 30 min of stimulation applied to the upper-limb muscles, including the deltoid, biceps brachii, and triceps brachii; the external oblique as a core muscle; and the vastus lateralis as a lower-limb muscle. The control group completed the same time-matched assessment without NMES. Three-dimensional kinematic data were collected using a synchronized four-camera three-dimensional motion-analysis system. The primary analysis compared performance and kinematic variables between the groups at the second assessment. Compared with the control group, the NMES group demonstrated greater ball velocity, smaller knee and ankle angles at bilateral-foot contact, greater hip, knee, and ankle angles at bilateral take-off, and higher thigh, calf, and foot segmental velocities. The NMES group also showed a smaller shoulder-hip separation angle at bilateral take-off and ball contact. These findings indicate that acute NMES priming applied to upper-limb, core, and lower-limb muscles may influence phase-specific joint configurations, lower-limb segmental velocities, and ball velocity during volleyball spiking. NMES may therefore have potential as a pre-performance neuromuscular activation strategy, although further studies using concealed allocation, blinded assessment, and direct group-by-time analyses are required.