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

Abstract

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.

Effects of Consecutive Rebound Jump Training Dependent on Muscles to which Electromyostimulation is applied

“…After training, a close relationship was observed between the rate of increase in the Achilles tendon stiffness and that in jump height of RJ in the EMS CALF group, and only this group developed a clear "bounce" sensation during jumping after training. These results agree with those in our previous study [15] and suggest that EMS to the calf muscle elicited the Achilles tendon recoil more effectively during jumps and enhanced the characteristics of SSC exercise in which the MTC stretching phase plays an important role [28,29]. The application of EMS to the anterior thigh or all thigh muscles did not develop a clear "bounce" sensation during jumping after training, but increased MVIC torques especially in the leg extension position and its jump height.…”

“…The RJ, EMS intensity settings and their superimposition methods were based on those presented by Ogiso and Miki [15]. All participants were instructed to jump at maximum effort in the same spot with their hands on their waist and received no technical advice on jumping.…”

“…The electrodes were wetted with a moderate amount of water, and the anode and cathode were placed at the proximal and distal ends of the target muscles, respectively. The EMS frequency was set to 20 Hz for the following reasons: 1) unstable muscle tension at frequencies lower than 20 Hz, 2) immediate muscle fatigue at frequencies higher than 50 Hz [23], and 3) light kinesthetic sensations during jumps at a 20 Hz [15]. The pulse width was set to 260 µs because the participants in a preliminary experiment felt that it was easier to jump with that pulse width.…”

“…Jump height and its ground contact time, MVIC torque, and elongation of the Achilles tendon were measured to evaluate the effects of training, as in a previous study [15], before the start of the training period (Pre), immediately after the training period (Post), and one week after the end of the training period (1W). A counter movement jump (CMJ), a drop jump (DJ) from a height of 30 cm, and 10 RJs were performed on a mat (PH-1260, DKH, Tokyo, Japan).…”

“…These characteristics of EMS suggest that it could also be effective in improving jumping ability, depending on the use of EMS. In fact, consecutive RJ training performed while superimposing EMS on the calf muscle increased muscle strength in the dorsi exed position and Achilles tendon stiffness in a short period and with a small amount of training, and enhanced jump performance while inducing feelings of lightness and bounciness during jumps [15]. Human gait e ciency is improved by the elasticity of the Achilles tendon caused by approximately isometric contraction force of the calf muscle during ground contact phase [16].…”