Effect of work intensity and duration on recovery O2.

This study was undertaken to determine the effects of exercise intensity and duration on the time course and magnitude of recovery O2. Eighteen men exercised at 50, 65, and 80% of maximal O2 consumption (VO2max) for 5 and 20 min. Each exercise bout was preceded and followed by cycling at 150 kpm.min-1, which established the base-line VO2 used in this study. The magnitude of the rapid component of recovery O2 was proportional to exercise intensity and was not altered by exercise duration. The slow component of recovery O2 was not significantly altered by exercise intensity or duration at 50 and 65% of VO2max. However, after 20 min of exercise at 80% of VO2max, the slow component of recovery 02 was 5 times (p less than 0.01) larger than after the 5-min exercise at 80% of VO2max. End-exercise blood lactate level was also higher after the 20-min bout at 80% of VO2max; however, at most, 30% of the difference between the magnitude of the slow components of recovery O2 after the 5- and 20-min rides at 80% of VO2max could be accounted for by lactate metabolism. The Q10 effect of temperature on metabolism could account for 60-70% of the slow components of recovery O2 at all work rates and durations. It could also account for the remaining 70% of the increase in the slow component after the 20-min exercise at 80% of VO2max.