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This Article Full Text Full Text (PDF) All Versions of this Article: 586/3/889    most recent jphysiol.2007.142026v1 Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Google Scholar Articles by Jones, A. M. Articles by Fulford, J. PubMed PubMed Citation Articles by Jones, A. M. Articles by Fulford, J. Related Collections Skeletal Muscle and Exercise

¹ School of Sport and Health Sciences, St Luke's Campus, University of Exeter, Heavitree Road, Exeter EX1 2LU, UK

The kinetics of pulmonary O₂ uptake is known to be substantially slower when exercise is initiated from a baseline of lower-intensity exercise rather than from rest. However, it is not known whether putative intracellular regulators of mitochondrial respiration (and in particular the phosphocreatine concentration, [PCr]) show similar non-linearities in their response dynamics. The purpose of this study was therefore to investigate the influence of baseline metabolic rate on muscle [PCr] kinetics (as assessed using ³¹P-magnetic resonance spectroscopy) following the onset of exercise. Seven male subjects completed ‘step’ tests to heavy-intensity exercise (80% of peak work-rate) from a resting baseline and also from a baseline of moderate-intensity exercise (40% of peak work-rate) using a single-leg knee-extensor ergometer situated inside the bore of a 1.5 T super-conducting magnet. The time constant describing the kinetics of the initial exponential-like fall in [PCr] was significantly different between rest-to-moderate (25 ± 14 s), rest-to-heavy (48 ± 11 s) and moderate-to-heavy exercise (95 ± 40 s) (P < 0.05 for all comparisons). A delayed-onset ‘slow component’ in the [PCr] response was observed in all subjects during rest-to-heavy exercise, but was attenuated in the moderate-to-heavy exercise condition. These data indicate that muscle [PCr] kinetics does not conform to ‘linear, first-order’ behaviour during dynamic exercise, and thus have implications for understanding the regulation of muscle oxidative metabolism.

(Received 31 July 2007; accepted after revision 29 November 2007; first published online 6 December 2007)
Corresponding author A. M. Jones: School of Sport and Health Sciences, St Luke's Campus, University of Exeter, Heavitree Road, Exeter EX1 2LU, UK. Email: a.m.jones{at}exeter.ac.uk

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				C. Menuet and L. M. Arsac Muscle [phosphocreatine] dynamics during exercise: implication for understanding the regulation of muscle oxidative metabolism J. Physiol., July 1, 2008; 586(13): 3027 - 3029. [Full Text] [PDF]