Effect of 8-week frequency-specific electrical muscle stimulation combined with resistance exercise training on muscle mass, strength, and body composition in men and women: a feasibility and safety study

In recent years, electrical muscle stimulation (EMS) devices have been developed as a complementary training technique that is novel, attractive, and time-saving for physical fitness and rehabilitation. While it is known that EMS training can improve muscle mass and strength, most studies have focused on the elderly or specific patient populations. The aim of this study was to investigate the effects of frequency-specific EMS combined with resistance exercise training for 8 weeks on muscle mass, strength, power, body composition, and parameters related to exercise fatigue. Additionally, we aimed to evaluate the feasibility and safety of EMS as an exercise aid to improve body composition. We recruited 14 male and 14 female subjects who were randomly assigned to two groups with gender parity (seven male and seven female/group): (1) no EMS group (age: 21.6 ± 1.7; height: 168.8 ± 11.8 cm; weight: 64.2 ± 14.4 kg) and (2) daily EMS group (age: 21.8 ± 2.0; height: 167.8 ± 9.9 cm; weight: 68.5 ± 15.5 kg). The two groups of subjects were very similar with no significant difference. Blood biochemical routine analysis was performed every 4 weeks from pre-intervention to post-intervention, and body composition, muscle strength, and explosive power were evaluated 8 weeks before and after the intervention. We also performed an exercise challenge analysis of fatigue biochemical indicators after 8 weeks of intervention. Our results showed that resistance exercise training combined with daily EMS significantly improved muscle mass (p = 0.002) and strength (left, p = 0.007; right, p = 0.002) and significantly reduced body fat (p < 0.001) than the no EMS group. However, there was no significant advantage for biochemical parameters of fatigue and lower body power. In summary, our study demonstrates that 8 weeks of continuous resistance training combined with daily upper body, lower body, and abdominal EMS training can significantly improve muscle mass and upper body muscle strength performance, as well as significantly reduce body fat percentage in healthy subjects.