Development and evaluation of functional muscle electrical stimulation for individuals with limited exercise capacity

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We have demonstrated that low frequency electrical stimulation (ES) of quadriceps muscles alone significantly enhanced glucose disposal rate (GDR) during euglycemic clamp. We further followed up to examine the acute metabolic effects of ES to lower extremities in comparison with voluntary cycle exercise (VE) at identical intensity. In eight male subjects lying in the supine position, both lower leg (tibialis anterior and triceps surae) and thigh (quadriceps and hamstrings) muscles were sequentially stimulated to co-contract in an isometric manner at 20Hz with a 1-s on-off duty cycle for 20min. Despite of small elevation of oxygen uptake by 7.3±0.3 ml/kg/min during ES, the blood lactate concentration was significantly increased by 3.2±0.3 mmol/l in initial period (5min) after the onset of the ES (P<0.01) whereas VE showed no such changes at identical oxygen uptake (7.5±0.3 ml/kg/min). ES also induced enhanced whole body carbohydrate oxidation as shown by the significantly higher respiratory gas exchange ratio than VE (P<0.01). These data indicated increased anaerobic glycolysis by ES. Furthermore, whole-body glucose uptake determined by GDR during euglycemic clamp demonstrated a significant increase during and after the cessation of ES for at least 90min (P<0.01). This post ES effect was significantly greater than that of post VE period (P<0.01). These results suggest that ES can substantially enhance energy consumption, carbohydrate oxidation and whole body glucose uptake at low intensity of exercise. Percutaneous ES may become therapeutic utility to enhance glucose metabolism in humans.