Effect of prior exercise above and below critical power on exercise to exhaustion

The aim of the present study was to ascertain whether the intensity of prior exercise altered the time to exhaustion at critical power (CP).

Eleven participants volunteered to take part in the study (mean +/- SD: VO2max 4.1 +/- 0.5 L x min(-1); age 30.1 +/- 7.2 yr; body mass 74.6 +/- 9.1 kg) and completed three trials to exhaustion at their CP under differing prior exercise conditions: 1) a control trial (CON); 2) a trial preceded by three 60-s efforts at 110% CP (severe); and 3) a trial preceded by three 73-s efforts at 90% CP (heavy). All trials followed a 5-min baseline at 50 W.

Time to exhaustion was significantly lengthened after prior heavy exercise (1071 +/- 18 s) when compared with CON (973 +/- 16 s, F = 9.53, P = 0.006). However, there was no effect on TTE after prior severe exercise (967 +/- 16 s). Oxygen deficit was significantly reduced from that in CON (3.8 +/- 0.2 L) after prior heavy (3.2 +/- 0.3 L) and prior severe exercise (3.1 +/- 0.3 L, F = 10.95, P = 0.001). Concurrently, there was a significant reduction in the magnitude of the VO2 slow component (SC) in the trials with prior exercise (197 +/- 34 and 126 +/- 19 mL x min(-1) after heavy and severe exercise, respectively) when compared with CON (223 +/- 31 mL x min(-1), F = 9.62, P = 0.006).

Prior heavy exercise does appear to improve the time to exhaustion at CP by approximately 10% and is associated with a reduction in the VO2 SC. However, the reduction in the SC, with no change in performance after prior severe exercise, suggests that a reduced SC may not necessarily lead to improved TTE.