Skeletal muscle ATP turnover and single fibre ATP and PCr content during intense exercise at different muscle temperatures in humans

The effect of temperature on skeletal muscle ATP turnover, pulmonary oxygen uptake and single fibre ATP and PCr content was studied during intense cycling exercise. Six healthy male subjects performed 6-min intense (¿50%LT-VO(2peak)) cycling, at 60 rpm, under conditions of normal (N) and elevated muscle temperature (ET). Muscle biopsies obtained from the vastus lateralis at rest, 2 and 6 min were analysed for homogenate ATP, PCr, lactate and glycogen, allowing estimation of anaerobic ATP turnover. Freeze-dried single fibres from biopsies were characterised according to their myosin heavy chain composition (type I, IIA or IIAX) and analysed for ATP and PCr content. Pulmonary gas exchange was measured throughout. There was no difference in pulmonary oxygen uptake between the trials. The elevation of muscle temperature resulted in a lower (P¿