Relationship Between Increased Oxygen Uptake and Lactate Production With Progressive Incremental Electrode Skeletal Muscle Stimulation: A Pilot Study

Abstract

Background Belt electrode skeletal muscle stimulation (B-SES) is an alternative exercise therapy for those with difficulty performing voluntary exercise. However, it is unknown whether oxygen uptake (VO₂) in B-SES is comparable to cardiopulmonary exercise test (CPX) as assessed by voluntary exercise. This study aimed to evaluate oxygen uptake (VO₂) and lactate (LA) production in incremental B-SES compared to ergometer CPX and to determine the relationship with ergometer CPX. Methods This study included 10 healthy young Japanese participants. Using a crossover design, all participants underwent incremental B-SES CPX and ergometer CPX using a 20 W ramp. Serum lactic acid concentration (LA) was measured serially before, during, and after B-SES. The tolerability of B-SES was adjusted with the change in LA level (⊿LA). Results Peak VO₂ during B-SES (14.1±3.3 mL/kg/min) was significantly lower than ergometer peak VO₂ (30.2±6.2 mL/kg/min, P<0.001). B-SES peak VO₂ was similar to the anaerobic threshold (AT) VO₂ on ergometer CPX (15.1±2.6 mL/kg/min). LA (Rest: 1.4±0.3, Peak: 2.8±0.8 mmol) and plasma noradrenalin (Rest: 0.2±0.1, Peak: 0.4±0.1 ng/mL) levels increased after B-SES. No significant correlation was observed between B-SES peak VO₂ and ergometer CPX. However, after adjusting for B-SES, tolerability, it (peak VO₂ of B-SES /⊿LA) correlated with peak VO₂ (r=0.688, p=0.028) on the ergometer. Conclusion Peak VO₂ of the passively progressive B-SES almost reached the AT value of the ergometer CPX without adverse events. Peak VO₂ of B-SES adjusted with ⊿LA may be used to predict peak VO₂ in ergometer CPX.

Keywords: belt-like electrode skeletal muscle stimulation; cardiopulmonary exercise test; electric skeletal muscle stimulation; exercise tolerance; lactic acid; peak oxygen uptake.