Muscle [phosphocreatine] dynamics following the onset of exercise in humans: the influence of baseline work‐rate
- 1 February 2008
- journal article
- Published by Wiley in The Journal of Physiology
- Vol. 586 (3), 889-898
- https://doi.org/10.1113/jphysiol.2007.142026
Abstract
The kinetics of pulmonary O(2) 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 (31)P-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.This publication has 66 references indexed in Scilit:
- Influence of endurance training on muscle [PCr] kinetics during high-intensity exerciseAmerican Journal of Physiology-Regulatory, Integrative and Comparative Physiology, 2007
- 31P MR spectroscopy and in vitro markers of oxidative capacity in type 2 diabetes patientsMagnetic Resonance Materials in Physics, Biology and Medicine, 2006
- Effects of acute creatine kinase inhibition on metabolism and tension development in isolated single myocytesJournal of Applied Physiology, 2005
- Oxygen Exchange Profile in Rat Muscles of Contrasting Fibre TypesThe Journal of Physiology, 2003
- Effects of prior exercise on oxygen uptake and phosphocreatine kinetics during high‐intensity knee‐extension exercise in humansThe Journal of Physiology, 2001
- Intersample fluctuations in phosphocreatine concentration determined by 31P‐magnetic resonance spectroscopy and parameter estimation of metabolic responses to exercise in humansThe Journal of Physiology, 2000
- Metabolic and respiratory profile of the upper limit for prolonged exercise in manErgonomics, 1988
- Energetics of human muscle: Exercise‐induced ATP depletionMagnetic Resonance in Medicine, 1986
- Effect of varying exercise intensity on glycogen depletion in human muscle fibresActa Physiologica Scandinavica, 1985
- First-order kinetics of muscle oxygen consumption, and an equivalent proportionality between QO2 and phosphorylcreatine level. Implications for the control of respiration.The Journal of general physiology, 1985