Effects of prior heavy exercise, prior sprint exercise and passive warming on oxygen uptake kinetics during heavy exercise in humans
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Prior heavy exercise (above the lactate threshold, Thla) increases the amplitude of the primary oxygen uptake (VO2) response and reduces the amplitude of the VO2 slow component during subsequent heavy exercise. The purpose of this study was to determine whether these effects required the prior performance of an identical bout of heavy exercise, or if prior short-duration sprint exercise could cause similar effects. A secondary purpose of this study was to determine the effect of elevating muscle temperature (through passive warming) on VO2 kinetics during heavy exercise. Nine male subjects performed a 6-min bout of heavy exercise on a cycle ergometer 6 min after: (1) an identical bout of heavy exercise; (2) a 30-s bout of maximal sprint cycling; (3) a 40-min period of leg warming in a hot water bath at 42°C. Prior sprint exercise elevated blood [lactate] prior to the onset of heavy exercise (by ≅5.6 mM) with only a minor increase in muscle temperature (of ≅0.7°C). In contrast, prior warming had no effect on baseline blood lactate concentration, but elevated muscle temperature by ≅2.6°C. Both prior heavy exercise and prior sprint exercise significantly increased the absolute primary VO2 amplitude (by ≅230 ml·min–1 and 260 ml·min–1, respectively) and reduced the amplitude of the VO2 slow component (by ≅280 ml·min–1 and 200 ml·min–1, respectively) during heavy exercise, whereas prior warming had no significant effect on the VO2 response. We conclude that the VO2 response to heavy exercise can be markedly altered by both sustained heavy-intensity submaximal exercise and by short-duration sprint exercise that induces a residual acidosis. In contrast, passive warming elevated muscle temperature but had no effect on the VO2 response.
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