Kinetic Performance, Leg Stiffness and Gastrocnemius Muscle Activity During Shod and Barefoot Two-Legged Hopping in Elite Female Court Athletes

Background/Objectives: This study investigated kinetic performance, leg stiffness and gastrocnemius muscle (GM) activity during shod and barefoot two-legged hopping in female court athletes, while also assessing potential sport specialization-by-footwear interactions. Methods: Forty-two elite female Volleyball, Basketball, and Handball athletes (n = 14 per group) performed two-legged hopping at 130 bpm under both shod and barefoot conditions. Vertical ground reaction force (Fz) (Kistler forceplate sampling at 1000 Hz) was recorded in synchronization with GM vibromyographic intensity (TSD250, Biopac Systems, sampling at 2000 Hz). Kinetic metrics, kleg and GM activation were analyzed via repeated-measures ANOVA (alpha = 0.05, PSS 30.0). For all metrics, results indicated no significant sport-by-footwear interaction (p > 0.05). Results: Footwear significantly altered hopping kinematics; while absolute contact durations remained constant, relative total and effective contact durations were elongated and shortened, respectively. In the shod condition, kleg increased (+6.1%, p < 0.05) alongside a reduction in GM activation (−7.7%, p < 0.05). Additionally, Fz peak increased (+4.3%, p < 0.05) and occurred relatively earlier in the contact phase (−0.7%, p < 0.05). Conclusions: These findings indicate that footwear acts as a mechanical buffer, enabling a stiffer leg spring and reduced neuromuscular demand. The earlier timing of Fz peak suggests a facilitated eccentric-to-concentric transition, most likely allowing athletes to maintain efficient energy return despite the compliance of the footwear interface.