Over 55 years of critical power: Fact or artifact?

This report aims to generate an evidence‐based debate of the Critical Power (CP), or its analogous Critical Speed (CS), concept. Race times of top Spanish runners were utilized to calculate CS based on three (1500‐m to 5000‐m; CS 1.5‐5km ) and four (1500‐m to 10000‐m; CS 1.5‐10km ) distance performances. Male running world records from 1000 to 5000‐m (CS 1‐5km ), 1000 to 10,000‐m (CS 1‐10km ), 1000‐m to half marathon (CS 1km‐half marathon ), and 1000‐m to marathon (CS 1km‐marathon ) distance races were also utilized for CS calculations. CS 1.5‐5km (19.62 km h −1 ) and CS 1.5‐10km (18.68 km h −1 ) were different ( p < 0.01), but both approached the average race speed of the longest distance chosen in the model, and were remarkably homogeneous among subjects (97% ±1% and 98% ±1%, respectively). Similar results were obtained using the world records. CS values progressively declined, until reaching a CS 1km‐marathon value of 20.77 km h −1 (10% lower than CS 1‐5km ). Each CS value approached the average speed of the longest distance chosen in the model (96.4%–99.8%). A power function better fitted the speed‐time relationship compared with the standardized hyperbolic function. However, the horizontal asymptote of a power function is zero. This better approaches the classical definition of CP: the power output that can be maintained almost indefinitely without exhaustion. Beyond any sophisticated mathematical calculation, CS corresponds to 95%–99% of the average speed of the longest distance chosen as an exercise trial. CP could be considered a mathematical artifact rather than an important endurance performance marker. In such a case, the consideration of CP as a physiological “gold‐standard” should be reevaluated.