Influence of priming exercise on pulmonary O 2 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 (V̇o 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 V̇o 2 time constant (τ) 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 τ 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 V̇o 2 kinetics were only evident when muscle O 2 extraction (measured as Δ[deoxyhemoglobin]/ΔV̇o 2 ) was elevated in the fundamental response phase. These data indicate that prior high-intensity exercise at a high pedal rate can speed V̇o 2 kinetics during subsequent high-intensity exercise, presumably through specific priming effects on type II muscle fibers.