Background: Electrical muscle stimulation is an effective tool that provides additional benefits to energy metabolism, such as energy expenditure. However, it remains unclear which energy system influences the increase in energy expenditure during electrical muscle stimulation. The aim of this study was to determine the contribution of three energy systems (aerobic, anaerobic lactic, and anaerobic alactic) during a single session of weight-bearing exercise with EMS using a crossover randomized controlled trial.
Methods: Ten young females (mean age: 23.0±3.6 years) were randomly assigned to perform two types of exercises in a random order (WB: weight-bearing exercises without electrical muscle stimulation, N.=10; WB+EMS: weight-bearing exercises with electrical muscle stimulation, N.=10). During both sessions, we evaluated the oxygen consumption (absolute and relative), blood lactate concentration (before and after exercise), and heart rate. We then calculated the energy expenditure and percentage for the three energy systems.
Results: WB+EMS showed significantly higher oxygen consumption (P=0.016, effect size; d=0.94) than WB. The total energy expenditure was 25.7% higher in WB+EMS than in WB (84.4±17.1 vs. 67.1±15.4 kcal, P=0.045, d=0.74). In addition, the energy expenditure of the anaerobic lactic system was significantly higher in the WB+EMS (P=0.009, d=1.06).
Conclusions: These findings suggest that electrical muscle stimulation can contribute to an increased energy metabolism, particularly in the anaerobic energy system, even when performing the same type and duration of exercise.