Lactate acidosis and the increase in VE/VO2 during incremental exercise.

Abstract

The purpose of this investigation was to determine whether the onset of lactate acidosis is responsible for the increase in ventilatory equivalent (VE/VO2) during exercise of increasing intensity. Eight male subjects performed maximal incremental exercise tests on a cycle ergometer on two separate occasions. For the control (C) treatment, the initial work rates consisted of 4 min of unloaded pedaling (60 rpm) and 1 min of pedaling at a work rate of 30 W. Thereafter, the work rate was increased each minute by 22 W until volitional fatigue. Venous blood samples were taken before the onset of exercise and at the end of each work rate for determination of pH and lactate. Ventilatory parameters at each work rate were also monitored. Before the experimental treatment (E), the subjects performed two 3-min work bouts at high intensity (210-330 W) on the cycle ergometer in order to prematurely raise blood lactate levels and lower blood pH. The same incremental exercise test as C was then performed. The results indicated that the increase in VE/VO2 occurred at similar work rates and %VO2max although the venous H+ and lactate concentrations were significantly elevated during the E treatment. These results suggest that a decrease in the blood pH resulting from blood lactate accumulation is not responsible for the increase in VE/VO2 during incremental exercise.