The influence of electrostimulation on mechanical and morphological characteristics of the triceps surae

The present study assessed the effects of training using electrostimulation of muscle (EMS) on the torque‐angular velocity and torque‐angle relationships, and the cross‐sectional area (CSA) of the triceps surae. Twelve physical education students, divided into two groups (6 control, 6 experimental), participated in the experiment. The EMS sessions were undertaken using a ‘Compex‐type’ stimulator. Flexible elastomer electrodes were used. The current used discharged pulses lasting for 200 μs at a frequency of 70 Hz. The durations of contraction and rest were 5 and 15 s, respectively. The session lasted for 10 min for each muscle. The training regimen was three sessions per week for 4 weeks. Biomechanical tests were performed with the Biodex (Biodex Corporation, Shirley, NY, USA) isokinetic ergometer. Plantar flexions of the ankle over a concentric range of voluntary contractions were performed at different angular velocities (1.05, 2.10, 3.14, 4.20, 5.23 and 6.28 rad s^‐1) and maximum voluntary isometric contractions were held for 5 s at several ankle flexion angles (–30°, –15°, 0° and 15°; 0° corresponds to foot flexion of 90° relative to the leg axis). The peak value of the torque was recorded. Morphological tests consisted of measuring the CSA of the triceps surae on the right leg, 15 cm below the tibial protuberance, by a computerized tomography technique. The torque‐velocity relationship was seen to shift significantly upwards after EMS training. The increase in the isometric torque observed after EMS training was greater in dorsiflexion than in plantarflexion. No change was noted in the CSA of the muscle. It appears that the increase in strength following EMS training is not related to an increase in the contractile matter. These observations show that EMS training for 4 weeks develops dynamic and static contractile properties of the muscle. Neural mechanisms may account for these adaptations.