Effects of Integrating Wearable Resistance into Regular Volleyball Training on Countermovement Jump Performance and Kinematics During the In-Season Period

Background/Objectives: This study aimed to examine the effects of an eight-week wearable resistance (WR) training program on jump performance and jump kinematics in experienced senior female volleyball players. It was hypothesised that using WR would increase training load, thereby enhancing vertical jump performance and influencing kinematic movement patterns. Methods: Sixteen competitive female volleyball players (mean age: 23.5 ± 3.24 years; mean weight: 66.8 ± 6.9 kg; mean height: 174.7 ± 5.8 cm) participated in the study. Participants were randomly assigned to either a control group (n = 8) or an intervention group (n = 8) that trained with calf-mounted WR. The intervention group performed supervised resistance training sessions twice per week for eight weeks, totalling 16 sessions. Jump performance was assessed using an Infrared Optical Contact Grid (MuscleLab, Ergotest Innovation AS, Norway), and jump kinematics were measured with the Xsens Link motion capture system (Movella, The Netherlands). Results: The WR group demonstrated a statistically significant improvement in vertical jump height (p = 0.031), with no significant changes in kinematic variables. The control group, however, showed a significant increase in T8–pelvis flexion during the countermovement jump (CMJ) following the intervention period. Conclusions: Eight weeks of WR training can improve CMJ performance in-season among experienced female volleyball players without affecting movement kinematics. Future research should investigate optimal loading strategies and long-term adaptations. These findings suggest that integrating small wearable loads into regular volleyball practice can help athletes maintain and improve explosive performance without disrupting normal training routines.