The effect of reducing work rate on total work done and time to task failure during severe intensity exercise

This study assesses the finite work capacity (W') above critical power (CP) when work rate is reduced during severe intensity exercise and whether reducing work rate immediately prior to task failure allows continued work above CP.

14 cyclists performed three experimental trials. Two consisted of exercising at a fixed work rate (WR) that depleted 70% of W' in 90 s and 180 s respectively, after which work rate was reduced to CP + 20 W and continued until task failure. The third consisted of exercising at a fixed work rate to achieve task failure in 5 min (P₅) when work rate was reduced, and exercise continued until task failure. Work rate was reduced a further two times and continued until task failure. Predicted (WORK_PRED) and actual work above CP (WORK₉₀, WORK₁₈₀, WORK_P5) and predicted (TTE_PRED) and actual time to task failure (TTE₉₀, TTE₁₈₀, TTE_P5) for each of the trials were compared.

Compared to WORK_PRED, total work above CP was greater (P < 0.05) in all three trials [WORK₉₀ (+ 5.4 ± 0.7 kJ); WORK₁₈₀ (+ 4.3 ± 1.3 kJ); WORK_P5 (+ 2.7 ± 0.4 kJ)]. Compared to the respective predicted time, time to task failure was greater (P < 0.05) in all three trials [TTE₉₀ (+ 256 ± 38 s); TTE₁₈₀ (+ 240 ± 55s); TTE_P5 (+ 109 ± 12s)].

W' is not a fixed parameter. When W' was partially depleted work above CP continued more than predicted. Moreover, when W' is theoretically 0 kJ, work can continue above CP, if work rate is reduced.