Submitted on September 6, 2008
Revised on November 26, 2008
Accepted on November 27, 2008
Influence of priming exercise on pulmonary O2 uptake kinetics during transitions to high-intensity exercise at extreme pedal rates
Fred J. DiMenna1, Daryl P. Wilkerson1, Mark Burnley2, Stephen J Bailey1, and Andrew M. Jones1*
1 Exeter University
2 University of Wales, Aberystwyth
* To whom correspondence should be addressed. E-mail: a.m.jones{at}exeter.ac.uk.
We investigated the muscle fiber-type dependency of the effect of priming exercise on VO2 kinetics by using extreme pedal rates to alter fiber recruitment. 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, 35115, 11535, and 115115 rev.min-1). Pulmonary gas exchange and heart rate were measured breath-by-breath and muscle oxygenation was assessed using near-infrared spectroscopy (NIRS). When the priming bout was performed at 35 rev.min-1 (3535 and 35115 conditions), the phase II VO2 time constant (
) 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-1 (11535 and 115115 conditions), the phase II 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 following priming exercise in all four conditions, but significant effects on VO2 kinetics were only evident when muscle O2 extraction (estimated as 
[deoxyhemoglobin]/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.
