ATP Turnover And The Coupling Of Mitochondrial Oxidative Phosphorylation During Dynamic Exercise In Humans

To determine ATP turnover rate during sub- and supra-LT CWR exercise in humans. Seven healthy participants completed a series of prone, knee-extension, rest-exercise-rest protocols using a computer-controlled ergometer in a 3T superconducting magnet. super(31)P spectra (3200 Hz bandwidth; 1024 data points; 2 s TR) were collected from the quadriceps throughout using a dual-tuned ( super(1)H and super(31)P) surface coil. Pulmonary VO sub(2) was measured breath-by-breath using a mass spectrometer and turbine. During MOD there was no discernable VO sub(2sc) (0.07 + or - 0.15 L.min super(-1)). Conversely, during HVY the VO sub(2sc) was larger (p < 0.05) at 0.32 + or - 0.11 L.min super(-1) or 20 + or - 6 % of the fundamental VO sub(2) amplitude. Similarly, the difference in PCr between 3 and 8 min of MOD was minimal (-2.8 + or - 4.0 mM), whereas this difference was larger (p < 0.05) during HVY (2.1 + or - 1.5 mM or 17 + or - 13 % of the fundamental amplitude). Three of seven participants exhibited a non-linear PCr/VO sub(2) relationship.