Effects of prior exercise on oxygen uptake and phosphocreatine kinetics during high‐intensity knee‐extension exercise in humans
HB Rossiter, SA Ward, JM Kowalchuk… - The Journal of …, 2001 - Wiley Online Library
The Journal of physiology, 2001•Wiley Online Library
1 A prior bout of high‐intensity square‐wave exercise can increase the temporal adaptation
of pulmonary oxygen uptake (V̇O2) to a subsequent bout of high‐intensity exercise. The
mechanisms controlling this adaptation, however, are poorly understood. 2 We therefore
determined the dynamics of intramuscular [phosphocreatine]([PCr]) simultaneously with
those of V̇O2 in seven males who performed two consecutive bouts of high‐intensity
square‐wave, knee‐extensor exercise in the prone position for 6 min with a 6 min rest …
of pulmonary oxygen uptake (V̇O2) to a subsequent bout of high‐intensity exercise. The
mechanisms controlling this adaptation, however, are poorly understood. 2 We therefore
determined the dynamics of intramuscular [phosphocreatine]([PCr]) simultaneously with
those of V̇O2 in seven males who performed two consecutive bouts of high‐intensity
square‐wave, knee‐extensor exercise in the prone position for 6 min with a 6 min rest …
- 1A prior bout of high‐intensity square‐wave exercise can increase the temporal adaptation of pulmonary oxygen uptake (V̇O2) to a subsequent bout of high‐intensity exercise. The mechanisms controlling this adaptation, however, are poorly understood.
- 2We therefore determined the dynamics of intramuscular [phosphocreatine] ([PCr]) simultaneously with those of V̇O2 in seven males who performed two consecutive bouts of high‐intensity square‐wave, knee‐extensor exercise in the prone position for 6 min with a 6 min rest interval. A magnetic resonance spectroscopy (MRS) transmit‐receive surface coil under the quadriceps muscle allowed estimation of [PCr]; V̇O2 was measured breath‐by‐breath using a custom‐designed turbine and a mass spectrometer system.
- 3The V̇O2 kinetics of the second exercise bout were altered compared with the first such that (a) not only was the instantaneous rate of V̇O2 change (at a given level of V̇O2) greater but the phase II τ was also reduced ‐ averaging 46.6 ± 6.0 s (bout 1) and 40.7 ± 8.4 s (bout 2) (mean ±s.d.) and (b) the magnitude of the later slow component was reduced.
- 4This was associated with a reduction of, on average, 16.1 % in the total exercise‐induced [PCr] decrement over the 6 min of the exercise, of which 4.0 % was due to a reduction in the slow component of [PCr]. There was no discernable alteration in the initial rate of [PCr] change. The prior exercise, therefore, changed the multi‐compartment behaviour towards that of functionally first‐order dynamics.
- 5These observations demonstrate that the V̇O2 responses relative to the work rate input for high‐intensity exercise are non‐linear, as are, it appears, the putative phosphate‐linked controllers for which [PCr] serves as a surrogate.
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