Effect of low-intensity leg exercise on ventilatory threshold during incremental arm exercise.

It is known that lactate, the level of which is increased during exercise, disappears more rapidly during low-intensity exercise than during passive recovery (Belcastro and Bonen, 1975; Stamford et al., 1981). This is because lactate can be used as an energy source during low-intensity exercise. If lactate can be used in such a way, it is supposed that the lactate that is produced during high-intensity exercise would disappear more rapidly during simultaneous low-intensity exercise. Therefore, in this study, we had subjects perform both incremental arm exercise and low-intensity steady-state leg exercise at the same time. This protocol was adopted for the following reason. During incremental exercise, if lactate elimination is affected by simultaneous leg exercise, it is supposed that the lactate threshold (LT), the point at which lactate production exceeds elimination, would also be affected. However, because arm exercise was performed, it was difficult to obtain blood samples from the fingertip. Therefore, we used respiratory gas kinetics to examine the effect of low-intensity leg exercise on ventilatory threshold (VT) during incremental arm exercise.