How Priming Exercise Affects Oxygen Uptake Kinetics: From Underpinning Mechanisms to Endurance Performance

Abstract

The observation that prior heavy or severe-intensity exercise speeds overall oxygen uptake ($$\dot{V}$$ V ˙ O2) kinetics, termed the “priming effect”, has garnered significant research attention and its underpinning mechanisms have been hotly debated. In the first part of this review, the evidence for and against (1) lactic acidosis, (2) increased muscle temperature, (3) O2 delivery, (4) altered motor unit recruitment patterns and (5) enhanced intracellular O2 utilisation in underpinning the priming effect is discussed. Lactic acidosis and increased muscle temperature are most likely not key determinants of the priming effect. Whilst priming increases muscle O2 delivery, many studies have demonstrated that an increased muscle O2 delivery is not a prerequisite for the priming effect. Motor unit recruitment patterns are altered by prior exercise, and these alterations are consistent with some of the observed changes in $$\dot{V}$$ V ˙ O2 kinetics in humans. Enhancements in intracellular O2 utilisation likely play a central role in mediating the priming effect, probably related to elevated mitochondrial calcium levels and parallel activation of mitochondrial enzymes at the onset of the second bout. In the latter portion of the review, the implications of priming on the parameters of the power–duration relationship are discussed. The effect of priming on subsequent endurance performance depends critically upon which phases of the $$\dot{V}$$ V ˙ O2 response are altered. A reduced $$\dot{V}$$ V ˙ O2 slow component or increased fundamental phase amplitude tend to increase the work performable above critical power (i.e. W´), whereas a reduction in the fundamental phase time constant following priming results in an increased critical power.

Running Critical Power and W´: Influence of the Environment, Timing and Time Trial Order

“…Therefore, although a 30-min period has been considered enough to recover from a previous severe exercise effort 15 , the lower power output observed when the 9-min was performed last could be explained by this fact. Lastly, a greater power output could have been observed on the last time trial performed according to the priming effect caused by the previous time trial 14 . This effect has been reported to be present for up to 45-min after a moderate or severe intensity effort, although according to our results, there is no consensus yet regarding the ideal intensity and recovery duration to induce significant performance improvements 14 .…”

“…Lastly, a greater power output could have been observed on the last time trial performed according to the priming effect caused by the previous time trial 14 . This effect has been reported to be present for up to 45-min after a moderate or severe intensity effort, although according to our results, there is no consensus yet regarding the ideal intensity and recovery duration to induce significant performance improvements 14 .…”

“…Regarding the timing of the time trials, a higher or lower performance could have been observed on the last time trial performed according to the recovery state and the priming effect caused by the previous time trial 14 . On the one hand, a greater fatigue could be expected between performing the 9- or the 3-min time trial first.…”

“…Likewise, athletes’ performance might be potentiated by the priming effect that the previous intense exercise bout causes on the kinetics of oxygen uptake 14 . On the one hand, if the time constant of the primary phase is reduced, the CP would increase 14 . On the other hand, if the rate of the slow component is reduced, the time to exhaustion would increase and therefore W´ 14 .…”

“…On the one hand, if the time constant of the primary phase is reduced, the CP would increase 14 . On the other hand, if the rate of the slow component is reduced, the time to exhaustion would increase and therefore W´ 14 . As a result, it is necessary to determine the impact that the order of the time trial has on the CP and W´ estimation.…”