Received December 20, 2007
Revised January 10, 2008
Accepted after revision January 25, 2008
Human, Environmental & Exercise [250]
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Influence of prior exercise on muscle [phosphocreatine] and deoxygenation kinetics during high-intensity exercise in humans
Andrew M. Jones 1*,
Jonathan Fulford 1,
Daryl P Wilkerson 1
1 University of Exeter
* To whom correspondence should be addressed. E-mail: a.m.jones{at}exeter.ac.uk.
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Abstract |
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31phosphate-magnetic resonance spectroscopy and near infra-red spectroscopy (NIRS) were used for the simultaneous assessment of changes in quadriceps muscle metabolism and oxygenation during consecutive bouts of high-intensity exercise. Six male subjects completed two 6-min bouts of single-leg knee-extension exercise at 80% of the peak work rate separated by 6-min of rest while positioned inside the bore of a 1.5 T super-conducting magnet. The total haemoglobin and oxyhaemoglobin concentrations in the area of the quadriceps muscle interrogated with NIRS was significantly higher in the baseline period prior to the second compared to the first exercise bout, consistent with an enhanced muscle oxygenation. Intramuscular phosphorylcreatine concentration ([PCr]) dynamics were not different over the fundamental region of the response (time constant, Bout 1: 51±15 vs. Bout 2: 52±17 s). However, the [PCr] dynamics over the entire response were faster in the second bout (mean response time, Bout 1: 72±16 vs. Bout 2: 57±8; P<0.05), as a consequence of a greater fall in [PCr] in the fundamental phase and a reduction in the magnitude of the 'slow component' in [PCr] beyond 3 min of exercise (Bout 1: 10±6 vs. Bout 2: 5±3 %; P<0.05). These data suggest that the increased muscle O2 availability afforded by the performance of a prior bout of high-intensity exercise does not significantly alter the kinetics of [PCr] hydrolysis at the onset of a subsequent bout of high-intensity exercise. The greater fall in [PCr] over the fundamental phase of the response following prior high-intensity exercise indicates that residual fatigue acutely reduces muscle efficiency.
Key Words:
Exercise, Kinetics, VO2
