EFFECT OF ELECTRICAL-STIMULATION OF LEG MUSCLES ON PHYSIOLOGICAL-RESPONSES DURING ARM-CRANKING EXERCISE IN HEALTHY-MEN

The purpose of this study was to investigate the hypothesis that chang es in physiological responses during arm-cranking exercise using elect rical stimulation of the leg muscles (ACE-ES) compared to arm-cranking exercise alone (ACE) in able-bodied subjects (ABS) are based on an in crease in active muscle mass rather than the enhancing effect of the l eg muscle pump. In ABS the sympathetic nervous system induced vasocons triction and activity of the leg muscle pump are intact, therefore, a normal redistribution of blood takes place during exercise. Consequent ly, ES should have no additional effect on the redistribution of blood in these ABS during exercise and, thus, changes in physiological resp onses will be based on an increase in active muscle mass. A group of 1 1 ABS performed three maximal arm-cranking tests. In the first test pe ak power output (POpeak) was determined. The other tests were both sub maximal and maximal ACE, once with ACE-ES and once with ACE. The POpea k was not significantly different between ACE-ES and ACE. Oxygen uptak e (VO2) increased significantly during ACE-ES compared to ACE. Cardiac output (Q(c)), stroke volume (SV), heart rate and ventilation were no t significantly different during ACE-ES compared to ACE. Respiratory e xchange ratios were significantly lower during ACE-ES compared to ACE at 60% POpeak and at maximal exercise. In conclusion, ACE-ES caused si gnificant increases in VO2 with a lack of elevation in Q(c) and SV dur ing submaximal and maximal exercise in ABS. The results of this study suggest that changes in physiological responses during ACE-ES are base d on an increase in the active muscle mass rather than stimulation of the leg muscle pump.