A 3-min all-out cycling test is sensitive to a change in critical power

Purpose: The aim of this investigation was to test the hypothesis that a 3-min all-out cycling test would detect a change in critical power (CP) following a 4 week interval training intervention. 
Methods: Nine habitually active subjects completed a ramp test, two 3-min all-out tests to establish the end-power (EP) and the work done above EP (WEP), and three predicting trials to establish CP and W' using the work-time model (W = CP • t + W'). Following twelve supervised high-intensity interval training sessions over four weeks subjects repeated the testing procedures. 

Results: The CP increased in all subjects after training (Pre: 230 ± 53 W; Post: 255 ± 50 W; t8 = 7.47, P <0.001), with no statistically significant effect on the W' (Pre: 17.2 ± 4.2 kJ; Post: 15.5 ± 3.8 kJ; t8 = 2.03, P = 0.08). The all-out test EP was increased after training from 225 ± 52 W to 248 ± 46 W (t8 = 6.26, P <0.001). The EP and CP estimates before and after training were not different and were highly correlated (Pre: r = 0.96, P <0.001; Post: r = 0.95, P <0.001). In addition, the increase in EP was correlated with (r = 0.77, P = 0.016) and not different from (t8 = 0.60, P = 0.57) the increase in CP. There was no change in the WEP from pre- to post-training (t8 = 1.89, P = 0.10). 

Conclusion: The present study shows that the 3-min all-out test closely estimates critical power across a wide range of aerobic fitness and is sensitive to training-induced changes in critical power.