Ventilatory responses at the onset of passive movement and voluntary exercise with arms and legs

This study was undertaken to elucidate whether phase I appeared at the onset of voluntary and passive arm movements and to compare these results with those of similar leg movements. Instead of the conventional cranking exercise, seven male subjects performed alternately flexion-relaxation of both arms, extension-relaxation of both legs, and combined arm and leg exercise at the rate of about 60 min-1 for four breaths in a sitting position. Similar movements were accomplished passively by the experimenters. In all experiments, minute ventilation increased rapidly within the first breath after the onset of exercise. The difference of ventilation (delta value) between the mean of the first two breaths at the onset of voluntary exercise and that of five breaths during rest was significantly (P < 0.05) greater in arm (7.75 l min-1) than in leg (5.19 l min-1). Passive movement showed a similar tendency. Arm delta ventilation correlated highly (r = 0.74-0.91) with leg delta ventilation and the slope of the regression lines was about 1.2. Heart rate increased abruptly while cardiac output did not always increase rapidly at the onset of locomotion. Oxygen uptake in the voluntary leg exercise continued for 3 min was slightly but nonsignificantly higher than in the arm exercise, indicating the equality of the exercise intensity. In conclusion, ventilatory responses at the onset of the arm exercise are larger than those of the leg in both voluntary and passive conditions regardless of the muscle mass, suggesting the different neurogenic mechanism between arm and leg.