Effect of prior multiple-sprint exercise on pulmonary O2 uptake kinetics following the onset of perimaximal exercise

We hypothesized that the metabolic acidosis resulting from the performance of multiple-sprint exercise would enhance muscle perfusion and result in a speeding of pulmonary oxygen uptake ((V)over dotO(2)) kinetics during subsequent perimaximal-intensity constant work rate exercise, if O-2 availability represented a limitation to (V)over dotO(2) kinetics in the control (i.e., no prior exercise) condition. On two occasions, seven healthy subjects completed two bouts of exhaustive cycle exercise at a work rate corresponding to similar to105% of the predetermined (V)over dotO(2 peak), separated by 3x30-s maximal sprint cycling and 15-min recovery (MAX(1) and MAX(2)). Blood lactate concentration (means+/-SD: MAX,: 1.3+/-0.4 mM vs. MAX(2): 7.7+/-0.9 mM; P<0.01) was significantly greater immediately before, and heart rate was significantly greater both before and during, perimaximal exercise when it was preceded by multiple-sprint exercise. Near-infrared spectroscopy also indicated that muscle blood volume and oxygenation were enhanced when perimaximal exercise was preceded by multiple-sprint exercise. However, the time constant describing the primary component (i.e., phase II) increase in (V)over dotO(2) was not significantly different between the two conditions (MAX(1): 33.8 +/- 5.5 s vs. MAX(2): 33.2 +/- 7.7 s). Rather, the asymptotic "gain" of the primary (V)over dotO(2) response was significantly increased by the performance of prior sprint exercise (MAX(1): 8.1 +/- 0.9 ml.min(-1).W-1 vs. MAX(2): 9.0 +/- 0.7 ml.min(-1).W-1; P<0.05), such that (V)over dotO(2) was projecting to a higher "steady-state" amplitude with the same time constant. These data Suggest that priming exercise, which apparently increases muscle O-2 availability, does not influence the time constant of the primary-component (V)over dotO(2) response but does increase the amplitude to which (V)over dotO(2) may rise following the onset of perimaximal-intensity cycle exercise.