Efficacy of Belt Electrode Skeletal Muscle Electrical Stimulation on Muscle Flexibility of Lower Limbs: A Randomized Controlled Pilot Trial

Background: Muscular contracture may be caused by immobility-induced muscle atrophy and skeletal muscle hypoxia. Belt electrode skeletal muscle electrical stimulation (B-SES) is a new type of neuromuscular electrical stimulation that can simultaneously contract the lower limb muscle groups, in contrast to the conventional pad-type electrodes. B-SES can suppress muscular atrophy and relieve hypoxia of the skeletal muscle and is considered an appropriate strategy for preventing muscular contracture. However, the effect of B-SES on muscle flexibility has not been verified. This study aimed to compare the immediate effects of B-SES on skeletal muscle flexibility using different stimulation modes before the clinical study.

Methods: We conducted a randomized controlled pilot trial with cross-over analysis of 10 healthy subjects. The participants were subjected to three stimulus conditions (Disuse B-SES, Metabolic B-SES, and Control) with a minimal interval of 1 day between interventions, and the lower limb flexibility before and after the B-SES intervention was evaluated. Lower extremity flexibility was evaluated based on the hamstring muscle stiffness and sit-and-reach distance. For each endpoint, within-group comparisons were performed before and after the intervention and were compared between the groups using paired t-tests. Changes in each endpoint before and after the intervention were analyzed using repeated-measures analysis of variance and the Bonferroni method. The significance level was 0.05.

Results: Ten healthy individuals participated in all three interventions with a washout period between each intervention. In the Metabolic B-SES group, the sit-and-reach distance after the intervention was significantly higher than that before the intervention (P < 0.05). A comparison of the change in the sit-and-reach distance among the three groups before subsequent tests showed that the Metabolic B-SES group had a significantly increased sit-and-reach distance compared with the control group (P < 0.05).

Conclusion: Metabolic B-SES was effective for the immediate improvement of flexibility of the lower limb muscles. Therefore, Metabolic B-SES may be useful as a strategy for preventing muscular contracture.