Physiological Responses of Combining Electrical Stimulation of the Thighs with Voluntary Arm Exercise on the NuStep®

Abstract

PURPOSE: The purpose of this study was to determine the impact on VO2 and surface electromyography (sEMG) of performing voluntary submaximal and maximal arm exercise combined with neuromuscular electrical stimulation (NMES) of the knee extensors on the NuStep® ergometer in able-bodied (AB) volunteers. The protocols and results of this study will be used to aid in exercise research for spinal cord injured (SCI) individuals. Eight college-aged participants completed five separate testing sessions. METHODS: The metabolic and sEMG responses were assessed during an arms only VO2peak test, a second VO2peak test with NMES applied to the knee extensors, during two, 15-minute submaximal steady-state bouts of exercise combined with NMES that would evoke 25lbs or 50lbs of isometric force, and during a voluntary legs only bout of exercise. RESULTS: We found that when NMES was combined with arms only exercise on the NuStep® during maximal exercise, VO2peak increased .34 L/min and power output increased 27watts (W). During submaximal exercise, VO2 increased .12 L/min with 25lbs of NMES and power output increased 6W. With 50lbs of NMES, VO2 increased .21 L/min and power output increased 9W. The arm sEMG responses indicated that there was no change in work performed by the arms when NMES was added during the submaximal exercise bouts. CONCLUSIONS: These findings indicate that the NuStep® offers SCI individuals the ability to increase their VO2 peak in a faster, more efficient way and stimulates central training adaptations by causing an increase in the metabolic intensity as a result of the increase in active muscle mass and power output via NMES.