This study aimed to assess the level of agreement between internal (i.e., oxygen uptake, heart rate, or ratings of perceived exertion) and external load markers (power output) at critical power intensity, compared to the first ventilatory threshold, respiratory compensation point, and maximum oxygen uptake derived from the cardiopulmonary exercise test, and estimate critical power from values derived from the cardiopulmonary exercise test in trained cyclists. Fourteen (13 males and 1 female) road master cyclists completed a cardiopulmonary exercise test to determine the first ventilatory threshold, respiratory compensation point, and maximum oxygen uptake. On a subsequent day, they completed three maximal time-trial tests to estimate critical power and W`. Associated physiological and perceptual values at critical power were estimated from linear regressions applied to the cardiopulmonary exercise test results. Internal and external markers significantly (p<0.05) increased from the first ventilatory threshold to the respiratory compensation point and then maximum oxygen uptake. There were no significant differences between internal and external markers at the respiratory compensation point vs. critical power with strong correlations between responses. However, there was a mean bias for responses at respiratory compensation point markers to overestimate some responses at critical power (power output and oxygen uptake by ~8%). This study shows that critical power can be estimated from a single cardiopulmonary exercise test. While the respiratory compensation point is not a reliable critical power substitute, predictive equations improve its estimation for more precise prescriptions in trained cyclists.
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