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 (VO2) 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 VO2 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 VO2 kinetics were only evident when muscle O2 extraction (measured as delta[deoxyhemoglobin]/delta VO2) was elevated in the fundamental response phase. These data indicate that prior high-intensity exercise at a high pedal rate can speed VO2 kinetics during subsequent high-intensity exercise, presumably through specific priming effects on type II muscle fibers.