Differences in countermovement and drop jump performance, kinetics and kinematics during barefoot and shod jumping in youth soccer players

This study compared performance, kinetic, and kinematic variables during the countermovement jump (CMJ) and drop jump (DJ) performed from different heights (8, 32, and 52 cm), under barefoot and athletic footwear conditions, in youth soccer players. Twenty-one male players completed CMJ and DJ trials on a force platform under both footwear conditions using a cross-sectional, within-session repeated-measures design with randomized ordering of footwear conditions and jump tests. Sagittal-plane kinematics of the hip, knee, and ankle were obtained through video analysis. During CMJ, athletic shoes conditions resulted in significantly greater jump height (p < 0.001, d = 1.08), peak velocity (p < 0.001, d = 1.03), and peak landing power (p = 0.008, d = 0.64) compared with barefoot. During DJs, DJ8 and DJ32 produced higher jump height (p = 0.004–0.027, d = 0.22–0.36), shorter ground contact times (p < 0.001–0.002, d = 0.45–0.66), and greater reactive strength index (both p < 0.001, d = 0.42–0.68) than DJ52, regardless of footwear condition, with no differences between DJ8 and DJ32. Peak contact force increased with drop height (all p < 0.001, d = 0.47–1.04) and was greater with athletic shoes than barefoot across drop heights (p = 0.030, ηp 2 = 0.214). During CMJ, greater ankle dorsiflexion and knee flexion were observed with athletic shoes (both p < 0.001, d = 1.08 and 1.62, respectively). During DJs, greater ankle and knee flexion were observed with athletic shoes (p = 0.004, ηp 2 = 0.349; p = 0.002, ηp 2 =0.391), whereas greater hip flexion was observed in the barefoot condition (p = 0.016, ηp 2 =0.257). Overall, differences were found on footwear condition in selected CMJ performance, DJ kinetic, and sagittal-plane kinematic outcomes, whereas DJ reactive performance was primarily changed by drop height.