Accentuated Eccentric Loading Increases Maximal Countermovement Jump Height Without Changes in Overall Lower Limb Kinetics and Energetics

This study aimed to determine the mechanical and energetic responses to accentuated eccentric loading (AEL) during maximal countermovement jumps (CMJ) and examined potential mechanisms underlying performance enhancement relative to bodyweight CMJs. We hypothesized that increased lower limb forces during loading would enhance positive work output during push-off. Fifteen recreationally active men with good jumping ability (22.3 ± 4.5 years, 1.85 ± 0.06 m, and 79.1 ± 9.6 kg) performed maximal CMJ with and without AEL using handheld dumbbells equivalent to 20% body mass. Compared with bodyweight CMJs, AEL CMJ increased (p < 0.05) effective jump height (d = 0.521), center-of-mass work (d = 0.405), mean vertical ground reaction force (d = 0.346), peak (d = 0.864) and mean (d = 0.647) center-of-mass velocity, and peak (d = 0.497) and mean (d = 0.541) center-of-mass power during the propulsive phase. Effective jump height increased by 2.1 cm with AEL (0.548 ± 0.046 m) compared with bodyweight CMJs (0.527 ± 0.036 m). However, total lower-limb joint work during push-off, squat depth, and most lower-limb electromyography parameters did not differ between conditions. Right ankle peak power and work during push-off were lower with AEL, indicating a reduced ankle contribution despite improved jump height. These results do not support the claim that AEL enhances lower-limb work output. Instead, increased center-of-mass work may have originated from segments not included in the joint-level analysis, such as the trunk and upper body. Our findings suggest the hypothesis that altered whole-body coordination, rather than greater lower-limb work, contributed to the performance enhancement.