Effects of electrical muscle stimulation on core muscle activation and physical performance in non-athletic adults: A randomized controlled trial

Abstract

Background: Electrical muscle stimulation (EMS) activates muscles through electrical currents, resulting in involuntary muscle contractions. This study aimed to evaluate the immediate clinical effects of superimposing EMS on strength training compared with conventional exercise in healthy non-athletic adults. Methods: This study was a randomised, controlled, parallel-group trial conducted at a single centre. Forty-one healthy young volunteers were recruited and randomised into two groups: strengthening with superimposed EMS (S+E) and strengthening (S) groups. All participants underwent the 30 minutes of strength training program, three times a week for 8 weeks, consisting of core muscle exercises. Additionally, the S+E group received EMS during training, which stimulated the bilateral abdominal, gluteus, and hip adductor muscles. As the primary outcome measure, we evaluated the changes in muscle thickness, including the abdominal, gluteal, and hip adductor muscles, using ultrasound. Muscle thickness was measured in both resting and contracted states. For secondary outcomes, physical performance (Functional Movement System score, McGill’s core stability test, and hip muscle power) and body composition analysis were evaluated. All assessments were performed at the beginning and end of the intervention. Results: 39 participants (S+E group = 20, S group = 19) completed the study. The clinical characteristics and baseline functional status of each group did not differ significantly between the groups. After completion of the training, the S+E group showed more efficient contraction in most of the evaluated muscles. The resting muscle thickness did not differ significantly between the groups; however, the contracted muscle thickness in the S+E group was higher than that in the S group (p < 0.05). Physical performance and body composition were not significantly different between the two groups. No intervention-related complications were reported during the study. Conclusion: EMS seems to be a safe and reasonable modality for improving physical fitness in healthy individuals.

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

“…Our study, similar to a previous study that combined 8 weeks of RT and EMS in untrained healthy adults and utilized the same BIA model for measuring body composition, observed a slight decrease in body fat mass in the RT combined with EMS group, while the RT alone group showed minimal change. However, these changes were not statistically significant in either within-group or between-group analyses ( Yoo et al, 2023 ). In our study, involving healthy adults undergoing RT with EMS, we observed a significant 4.33% reduction in body fat percentage in the daily EMS group compared to baseline, and these reductions were also significant when compared to the no EMS group ( Table 2 ).…”

“…Therefore, EMS exhibits similar benefits to traditional strength training in terms of improving muscle mass. However, the physiological effects and adaptations to muscle activation patterns in the neuromuscular system may differ between EMS and voluntary contractions ( Yoo et al, 2023 ). During voluntary contractions, motor unit recruitment follows the size principle, with small to large motor units being activated in a physiological manner.…”