Submitted on March 4, 2008
Revised on May 7, 2008
Accepted on May 23, 2008
Influence of priming exercise on pulmonary O2 uptake kinetics during transitions to high-intensity exercise from an elevated baseline
Fred J. DiMenna, Daryl P. Wilkerson, Mark Burnley, and Andrew M. Jones1*
1 Exeter University
* To whom correspondence should be addressed. E-mail: a.m.jones{at}exeter.ac.uk.
It has been suggested that the slower VO2 kinetics observed when exercise is initiated from an elevated baseline metabolic rate is linked to an impairment of muscle O2 delivery. We hypothesized that 'priming' exercise would significantly reduce the phase II time constant (
) during subsequent severe-intensity cycle exercise initiated from an elevated baseline metabolic rate. Seven healthy men completed exercise transitions to 70% of the difference between gas exchange threshold (GET) and peak VO2 from a moderate-intensity baseline (90% GET) on three occasions in each of the 'unprimed' and 'primed' conditions. Pulmonary gas exchange, heart rate and the electromyogram of m. vastus lateralis were measured during all tests. The phase II VO2 kinetics were slower when severe exercise was initiated from a baseline of moderate exercise compared to unloaded pedaling (mean ± SD , 42 ± 15 vs. 33 ± 8 s; P<0.05) but were not accelerated by priming exercise (42 ± 17 s; P>0.05). The amplitude of the VO2 slow component and the change in electromyogram from min 2 to 6 were both significantly reduced following priming exercise (VO2 slow component: from 0.47 ± 0.09 to 0.27 ± 0.13 L•min-1; 
iEMG6-2: from 51 ± 35 to 21 ± 42 % of baseline; P<0.05 for both comparisons). These results indicate that the slower phase II VO2 kinetics observed during transitions to severe exercise from an elevated baseline are not altered by priming exercise but that the reduced VO2 slow component may be linked to changes in muscle fiber activation.
