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

Purpose: The aim of the present study was to ascertain whether the intensity of prior exercise altered the time to exhaustion at critical power (CP). Methods: Eleven participants volunteered to take part in the study (mean +/- SD: VO2max 4.1 +/- 0.5 L-min(-1); age 30.1 +/- 7.2 yr; body mass gamma 4.6 +/- 9.1 kg) and completed three trials to exhaustion at their CP under differing prior exercise conditions: 1) a control trial (CON gamma; 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. Results: 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 compcnent (SC) in the trials with prior exercise (197 +/- 34 and 126 19 mL-min(-1) after heavy and severe exercise, respectively) when compared with CON (223 31 mL-min(-1), F = 9.62, P = 0.006). Conclusion: Prior heavy exercise does appear to improve the time to exhaustion at CP by similar to 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.