Modeling the power-duration relationship: the physiological and practical significance of the time constant parameter
Keywords:
anaerobic capacity, critical power, cycling performance, three-parameter model, two-parameter modelAbstract
In this paper, we discuss the physiological and practical significance of model parameters within the framework of the three-parameter critical power model, with particular emphasis on the time constant parameter. We show that reparametrizing Morton's formula results in a parameter set in which each parameter adjusts distinct parts of the power-duration curve and carries a strong physiological interpretation. Consistent with our hypothesis, we demonstrated using a large dataset that similar curvature constant (W’) values can arise from markedly different combinations of its underlying components. Therefore, we conclude that considering W’ in isolation is inherently ambiguous, unless the anaerobic power capacity as well as the time constant parameter are also considered. Moreover, we argue that the three-parameter critical power model provides a framework which enables an enhanced characterization of cyclists compared with the two-parameter critical power model. Finally, we discuss the potential practical applications of our findings for coaches, practitioners as well as scientists.
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