Influence of priming exercise on pulmonary O2 uptake kinetics during transitions to high-intensity exercise at extreme pedal rates.

We investigated the pedal rate dependency of the effect of priming exercise on pulmonary oxygen uptake (Vo(2)) kinetics. Seven healthy men completed two, 6-min bouts of high-intensity cycle exercise (separated by 6 min of rest) using different combinations of extreme pedal rates for the priming and criterion exercise bouts (i.e., 35-->35, 35-->115, 115-->35, and 115-->115 rev/min). Pulmonary gas exchange and heart rate were measured breath-by-breath, and muscle oxygenation was assessed using near-infrared spectroscopy. When the priming bout was performed at 35 rev/min (35-->35 and 35-->115 conditions), the phase II Vo(2) time constant (tau) was not significantly altered (bout 1: 31 +/- 7 vs. bout 2: 30 +/- 5 s and bout 1: 48 +/- 16 vs. bout 2: 46 +/- 21 s, respectively). However, when the priming bout was performed at 115 rev/min (115-->35 and 115-->115 conditions), the phase II tau was significantly reduced (bout 1: 31 +/- 7 vs. bout 2: 26 +/- 5 s and bout 1: 48 +/- 16 vs. bout 2: 39 +/- 9 s, respectively, P < 0.05). Muscle oxygenation was significantly higher after priming exercise in all four conditions, but significant effects on Vo(2) kinetics were only evident when muscle O(2) extraction (measured as Delta[deoxyhemoglobin]/DeltaVo(2)) was elevated in the fundamental response phase. These data indicate that prior high-intensity exercise at a high pedal rate can speed Vo(2) kinetics during subsequent high-intensity exercise, presumably through specific priming effects on type II muscle fibers.