REPEATED BOUTS OF FAST RAMP EXERCISE ARE NOT ASSOCIATED WITH CHANGES IN THE VO2-WORK RATE SLOPE

Abstract

The observation that a prior bout of heavy intensity, constant load exercise speeds pulmonary O2 (VO2) uptake kinetics during the on-transition of a subsequent exercise bout remains controversial. Compared to typical ramp exercise, fast ramp (FR) exercise is associated with an O2 uptake-work rate slope (i.e. Δ VO2/Δ WR) that is appreciably less than expected (∼ 10 ml/min/W) implying slowed VO2 kinetics. PURPOSE: This study examined the effect of successive bouts of fast ramp exercise to exhaustion on ΔVO2/ΔWR. METHODS: Seven male subjects (26 ± 5 yrs) performed successive bouts of ramp exercise to exhaustion. Following 4 min of 0 W pedaling, the WR was increased at 65 W/min (FR1). The subjects recovered for 7 min while cycling at 0 W before the initiation of the second ramp (FR2) at 65 W/min. Gas exchange was measured breath-by-breath. ΔVO2/Δ WR was determined using linear regression analysis after allowing for non-linearities in the VO2 response at the onset and end of the exercise. RESULTS: Compared to FR1 (839 ± 179 ml/min), baseline VO2 was higher at the onset of FR2 (1103 ± 186 ml/min). No difference in Δ VO2/Δ WR was observed between FR1 (8.37 ± 1.46 ml/min/W) and FR2 (8.37 ± 1.37 ml/min/W). The within-subject variability for Δ VO2/Δ WR was low (r = 0.99). CONCLUSION: The depressed but consistent Δ VO2/Δ WR observed during successive bouts of FR exercise is in agreement with the view that prior heavy exercise does not lead to a speeding of VO2 kinetics for this mode of exercise. Supported in part by NIH HL 46769 and MRC, Canada.