Consecutive rebound jump training with electromyostimulation of the calf muscle efficiently improves jump performance

We hypothesized that consecutive rebound jump (RJ) training with simultaneous electromyostimulation (EMS) of the calf muscles would more effectively improve jump performance than RJ training alone. Twenty-three men were divided into control, EMS, and non-EMS groups; the latter two groups performed consecutive two-leg RJ training every other day for 3 weeks. EMS was applied over the gastrocnemius muscles of both legs during jumping in the EMS group. RJ training with EMS significantly increased all types of jump height and the maximum voluntary isometric ankle plantar flexion (MVIC) torque in the dorsiflexion position and induced kinesthetic sensations of lightness and bounciness during jumps. Achilles tendon stiffness also tended to increase. In contrast, RJ training without EMS showed no such changes, with significant increases in RJ height and MVIC torque in the plantar flexion position alone. However, the EMS caused temporary soreness in the distal myotendinous junction of the gastrocnemius muscle. In conclusion, RJ training with EMS improves the mechanical properties of muscle and tendon tissue in a short period and enhances jump performance while inducing feelings of lightness and bounciness during jumps but also causes temporary muscle soreness.