The slow component of VO2 kinetics in very heavy and fatiguing square-wave exercise

We hypothesized that oxygen consumption (VO^sub 2^) rises incrementally in very heavy and fatiguing exercise where the slow component gain increases with higher work rates. Eight trained males completed a graded exercise test and bouts of square-wave cycle ergometry at 40% and 60% of the difference between the estimated lactate threshold (LT) and VO^sub 2peak^ (designated 40%D and 60%D). Exhaled gases were collected and analyzed every breath using models that allowed for a linear slow component or a slow component with one or more exponential increments. All subjects were able to complete 30 min at 40%D but not at 60%D. The slow component was generally best fit with two increments at 40%D and two or three increments at 60%D. In further ( , our results question the reliability of determining parameters of multiple slow component increments when repeated bouts are averaged together. This study demonstrates that VO^sub 2^ can continue to rise incrementally beyond the onset of the slow component in very heavy and fatiguing exercise. These results support the concept of a recurring mechanism underlying the slow component of VO^sub 2^ kinetics during square-wave exercise and suggest that the dynamics (time of onset, rate of development, magnitude) of this mechanism may vary from day to day. [PUBLICATION ABSTRACT]