In humans the oxygen uptake slow component is reduced by prior exercise of high as well as low intensity

The aim of the study was to examine to what extent prior high- or low-intensity cycling, yielding the same amount of external work, influenced the oxygen uptake (VO2) slow component of subsequent high-intensity cycling. The 12 subjects cycled in two protocols consisting of an initial 3 min period of unloaded cycling followed by two periods of constant-load exercise separated by 3 min of rest and 3 min of unloaded cycling. In protocol 1 both periods of exercise consisted of 6 min cycling at a work rate corresponding to 90% peak oxygen uptake (VO2peak). Protocol 2 differed from protocol 1 in that the first period of exercise consisted of a mean of 12.1 (SD 0.8) min cycling at a work rate corresponding to 50% VO2peak. The difference between the 3rd min VO2 and the end VO2 (deltaVO2(6-3)) was used as an index of the VO2 slow component. Prior high-intensity exercise significantly reduced deltaVO2(6-3). The deltaVO2(6-3) was also reduced by prior low-intensity exercise despite an unchanged plasma lactate concentration at the start of the second period of exercise. The reduction was more pronounced after prior high- than after prior low-intensity exercise (59% and 28%, respectively). The results of this study show that prior exercise of high as well as low intensity reduces the VO2 slow component and indicate that a metabolic acidosis is not a necessary condition to elicit a reduction in deltaVO2(6-3).