Author(s): ANDO, S., HASHIMOTO, Y., KANNO, I., KANO, K., ANJIKI, K., OGAWA, M., FUJIBAYASHI, M., SUDO, M., OKAMOTO, T., Institution: UNIVERSITY OF ELECTRO-COMMUNICATIONS, Country: JAPAN, Abstract-ID: 1638

INTRODUCTION:
Electrical muscle stimulation (EMS) has the potential to be an alternative modality to voluntary exercise [1]. However, less is understood how EMS applied to the lower limb muscles using belt electrodes influences quadriceps muscle strength and hypertrophy. Previous studies suggested that EMS activates mostly superficial motor units. Thus, we tested the specific hypothesis that changes in muscle strength and hypertrophy following EMS training are different from those following resistance exercise training. The purpose of this study was to examine effects of EMS and resistance exercise training on muscle strength and hypertrophy, and to compare the effects.
METHODS:
Thirty-six healthy male participants were divided into three groups; EMS training group (EMS group), resistance exercise training group (Resistance group), and control groups. In the EMS group, EMS was applied bilaterally to the abdomen, glutes, thighs, and lower legs with an electrical stimulator three times per week for eight weeks. The stimulator current waveform was set at 20 Hz with a pulse width of 0.25 ms. The cycle consisted of a two sec stimulation and a two sec pause. In the Resistance group, participants performed dynamic leg press training [2] for eight weeks. In the control group, participants maintained their lifestyle. Before and after the trainings, maximal isometric/isokinetic knee extension torque was measured using the Biodex dynamometer. Quadriceps muscle volume was assessed using magnetic resonance imaging.
RESULTS:
EMS training increased maximal isometric/isokinetic torque (p < 0.01), while leg press training only increased maximal isokinetic torque (p < 0.05). In the EMS group, muscle hypertrophy was observed at the distal part of the quadriceps muscle (p < 0.05). In the Resistance group, muscle hypertrophy was prominent around the muscle belly (p < 0.001).
CONCLUSION:
The present results indicate that EMS training has the potential to increase muscle strength. The lack of increases in isometric torque in the Resistance group suggests that the training effects were not transferred to isometric strength. The regional hypertrophy of the quadriceps muscle in the EMS group is presumably ascribed to current flows from knee to hip in the present experimental setup. The present results suggest that effects of EMS training using belt electrodes on muscle strength and hypertrophy are different from dynamic resistance exercise training.
[1] Akagi et al. (2024) J Sports Sci
[2] Neves et al. (2022) PLoS One