Unilateral Flywheel Training Enhances Eccentric Braking Capacity, Change-of-Direction Performance, and Match Acceleration–Deceleration in Soccer Players

Objectives: This study examined whether 8 weeks of unilateral flywheel resistance training (FRT) enhances eccentric neuromuscular characteristics and change-of-direction (COD) performance in male soccer players, and whether these adaptations transfer to sport-specific dribbling and match-play demands. Methods: Twenty-four male soccer players were randomized to a unilateral flywheel training group (EXT, n = 12) or a traditional resistance training control group (CON, n = 12). Both groups completed unilateral lower-limb strength training twice weekly for 8 weeks. Eccentric knee extensor and flexor peak torque (60°·s−1), eccentric-to-concentric (E:C) ratio, and inter-limb asymmetry were assessed using isokinetic testing. Performance measures included a 10 m sprint, modified 505, COD deficit, a dribbling-based COD test (AFL), and GPS-derived high-intensity acceleration and deceleration metrics during matches. Results: Compared with CON, the EXT group showed greater increases in knee extensor (+0.54 Nm·kg−1) and flexor (+0.46 Nm·kg−1) eccentric peak torque, a higher E:C ratio, and reduced inter-limb asymmetry (all p < 0.05). While 10 m sprint performance remained unchanged, EXT improved modified 505 performance and reduced COD deficits (up to −0.06 s). In addition, AFL completion time decreased and match-play high-intensity acceleration and deceleration events increased in EXT compared with CON (p < 0.05). Conclusions: Unilateral FRT effectively enhances eccentric braking-related capacity and COD efficiency, with clear transfer to soccer-specific technical performance and high-intensity match-play demands.