Neurovascular Correlates of Motor Imagery Training in Elite Volleyball Players: A Preliminary fNIRS Study

Background Motor imagery (MI) training is widely used to support motor learning, but it remains unclear whether mental training of complex sports-specific actions, like the volleyball spike serve, elicits a focal, training-induced hemodynamic activation increase in the primary motor cortex (M1). This preliminary study aimed to investigate the longitudinal effects of a 6 week complex mental training program focused on spike serve imagery on cortical activation in elite professional volleyball players, and to examine the spatial specificity of this adaptation using functional near-infrared spectroscopy (fNIRS). Methods Nine elite male professional volleyball players from a single team completed a 6 week, sport-specific MI training program targeting the spike serve within a longitudinal pre-test/post-test design. Cortical hemodynamic responses were recorded during a standardized block-design imagery task using a portable fNIRS system. Regions of interest on the primary motor cortex were anatomically defined based on the motor homunculus as Focal M1 (hand/arm representation), Dorsomedial M1 (dmM1; trunk/shoulder representation), and Ventrolateral M1 (vlM1; orofacial representation). Psychometric changes were assessed using the Sport Imagery Ability Questionnaire (SIAQ). Results Following the 6 week training, oxy-hemoglobin levels during the motor imagery condition significantly increased in the target Focal M1 region across both hemispheres (left: q < 0.0001; right: q = 0.021). This enhanced hemodynamic excitability extended to the adjacent dmM1 region but did not spread to the orofacial vlM1 area (q > 0.90), indicating that training-induced plasticity remained strictly specific to task-relevant anatomical representations. Furthermore, the improvement in self reported imagery ease, as indicated by SIAQ difference scores, was strongly and positively correlated (r = 0.960, q = 0.042) with the task-rest contrast change in the left Focal M1. Conclusions Six weeks of MI training enhances anatomically specific hemodynamic excitability in the primary motor cortex. The significant correlation between improved imagery ease and relative hemodynamic changes in the left M1 suggests that mental rehearsal of a complex, whole-body task like the spike serve engages left-lateralized praxis networks. These findings provide novel evidence that mental training induces highly focal cortical adaptations in elite athletes, extending the principle of somatotopically localized neuroplasticity to complex sports skills. Trial Registration Clinical trial number: not applicable.