A Single Sub-maximal 3-min Test For Critical Power Estimation

Abstract

Critical power (CP) demarcates heavy/sustainable from severe/unsustainable intensity exercise and is used for functional evaluation of exercise capacity and as a landmark for training design and exercise prescription. The gold standard measuring technique requires a physically demanding and time-consuming protocol (i.e., 3-5 constant-load trials to exhaustion) that may not be suitable in all contexts and populations. PURPOSE: We tested the hypothesis that CP can be accurately estimated based on blood lactate concentration ([LA]) determination at the third minute of a single submaximal non-exhausting cycle ergometer exercise. METHODS: Eight healthy men (26±2 years, 81±11 kg, 176±6 cm, 48±8 ml·Kg-1·min-1) performed five constant-power trials on a cycle ergometer, to the limit of intolerance, designed to generate a distribution of time-to-fatigue (tf) between ∼1 and 20 min. CP was calculated based on the individual watt–tf relationship. During each trial, [LA] was measure at rest and at 3 min from exercise onset and LA accumulation was calculated ([LA3min]) as the difference between 3-min and resting value. Based on individual trials >3 min in duration the [LA3min]–% of CP relationship was obtained and thereafter an estimate of CP (estCP) was computed. CP and estCP were compared by t-test, correlation, and Bland-Altman analysis. RESULTS: The group mean value of CP was 212 ± 37 watt. [LA3min] was a significant and linear function of the workload, expressed as % of CP (r2=0.82). estCP (212 ± 34 watt) was not significantly different from (p=0.90) and highly correlated with (r2=0.85) CP. The average difference (bias) between CP and estCP was -0.1 watt (not different from zero) with a precision of 14 watts. CONCLUSIONS: The data from this pilot study, on a small and homogeneous group of young men, indicate that CP can be accurately and precisely predicted based on a single submaximal non-exhausting trial and blood lactate concentration. Should these findings be confirmed in a larger and more heterogeneous population, they would offer a practical and valid alternative to direct CP determination. The knowledge of this functional parameter is of high practical utility as an indicator of the individual aerobic fitness as well as a quantitative instrument for exercise prescription.