Effects of unilateral vs. bilateral flywheel-based complex training on change-of-direction and sprint performance in elite male volleyball players

Background: Flywheel training has been shown to enhance lower-limb power; however, evidence comparing unilateral and bilateral complex training, especially among elite volleyball players, remains limited. Methods: Twenty-four male college volleyball players were randomly divided into three groups: unilateral flywheel complex training (UFT, n=8), bilateral flywheel complex training (BFT, n=8), or a control group (CON, n=8) that continued their regular technical training only. The intervention lasted 8 weeks, with 2 sessions each week. Performance measures included linear sprint times (5 m, 10 m, 30 m), change-of-direction skills (T-test, 5-0-5, volleyball-specific agility), and movement endurance (seven T-tests and repeated 30 m runs). A two-way repeated-measures ANOVA was performed to identify differences between groups and across time points (pre-test vs. post-test). Results: Significant group × time interactions were observed across sprint, COD, and repeated-movement tests (p < 0.05). UFT demonstrated greater improvements than both BFT and CON in short-distance sprint (5-10 m), COD performance, and repeated-movement measures. BFT also improved performance relative to CON in selected outcomes, particularly the 30 m sprint and repeated tests, although improvements were generally smaller than those observed in UFT. Conclusion: Eight weeks of unilateral flywheel-based complex training resulted in the greatest improvements in short sprints, COD, and movement endurance compared to bilateral training and the control group. Although bilateral training also enhanced performance, the gains were comparatively smaller. These findings support the effectiveness of UFT as a strategy for improving short-distance acceleration and multidirectional movement performance relevant to volleyball match play.