Time to exhaustion during cycling is not well predicted by critical power calculations.

Three to five cycling tests to exhaustion allow prediction of time to exhaustion (TTE) at any power-output based on calculation of critical power (CP). We aimed to determine the accuracy of CP predictions of TTE at power-outputs habitually endured by cyclists. Fourteen endurance-trained male cyclists underwent 4 randomized cycle-ergometer TTE tests at power-outputs eliciting, i) mean Wingate anaerobic test (WAnTmean), ii) VO2max, iii) respiratory compensation threshold (VT2) and iv) maximal lactate steady state (MLSS). Tests were conducted in duplicate with coefficient of variation of 5-9%. Power-outputs were 710±63 W for WAnTmean, 366±26 W for VO2max, 302±31 W for VT2 and 247±20 W for MLSS. Corresponding TTE were 00:29 ± 00:06, 03:23±00:45, 11:29±05:07 and 76:05±13:53 mm:ss, respectively. Power-output associated with CP was only 2% lower than MLSS (242±19 vs. 247±20 W; P<0.001). The CP predictions overestimated TTE at WAnTmean (00:24 ± 00:10 mm:ss) and MLSS (04:41 ± 11:47 mm:ss), underestimated TTE at VT2 (-04:18 ± 03:20 mm:ss; P<0.05) and correctly predicted TTE at VO2max. In summary, CP accurately predicts MLSS power-output and TTE at VO2max. However, it should not be used to estimate time to exhaustion in trained cyclists at higher or lower power-outputs (e.g., sprints and 40 km time trials). Novelty bullets: • Critical power (CP) calculation enables to predict time to exhaustion (TTE) at any cycling power-output • We tested those predictions against measured TTE in a wide range of cycling power-outputs. • CP appropriately predicted TTE at VO2max intensity but err at higher and lower cycling power-outputs.