Effects of interval and continuous training on O-2 uptake kinetics during severe-intensity exercise initiated from an elevated metabolic baseline

The purpose of this study was to test the hypothesis that VO2 kinetics would be speeded to a greater extent following repeated sprint training (RST), compared with continuous endurance training (ET), in the transition from moderate-to severe-intensity exercise. Twenty-three recreationally active subjects were randomly assigned to complete six sessions of ET (60-110 min of moderate-intensity cycling) or RST (four to seven 30-s all-out Wingate tests) over a 2-wk period. Subjects completed three identical work-to-work cycling exercise tests before and after the intervention period, consisting of baseline cycling at 20 W followed by sequential step increments to moderate-and severe-intensity work rates. The severe-intensity bout was continued to exhaustion on one occasion and was followed by a 60-s all-out sprint on another occasion. Phase II pulmonary VO2 kinetics were speeded by a similar magnitude in both the lower (ET pre, 28 +/- 4; ET post, 22 +/- 4 s; RST pre, 25 +/- 8; RST post, 20 +/- 7 s) and upper (ET pre, 50 +/- 10; ET post, 39 +/- 11 s; RST pre, 54 +/- 7; RST post, 40 +/- 11 s) steps of the work-to-work test following ET and RST (P = 0.05). The tolerable duration of exercise and the total amount of sprint work completed in the exercise performance test were also similarly enhanced by ET and RST (P = 0.05). Therefore, ET and RST provoked comparable improvements in VO2 kinetics and exercise performance in the transition from an elevated baseline work rate, with RST being a more time-efficient approach to elicit these adaptations.