Reliability of the durability concept in professional cyclists: a field-based study

Durability is increasingly recognized as a determinant of cycling performance. However, its reliability remains unknown. In this study, we assessed the repeatability of durability (determined as the decline in power output after accumulated work). We recorded the highest power output values (maximum mean power values) attained by 18 professional cyclists (27±4 y) during training and competition for different effort durations (10 s and 1, 5, 10, and 20 min) after different levels of accumulated work (0-40 kJ/kg) during a cycling season. Repeatability was examined through the standard error of measurement and the intra-class correlation coefficient calculated from the two highest maximum mean power values obtained by each cyclist for each duration and level of accumulated work. A progressive decline of maximum mean power values compared to the non-fatigued state was observed after higher levels of accumulated work, particularly after 20 kJ/kg (<i>p</i><0.001). All maximum mean power values showed high repeatability under fatigue states (all standard error of measurement<5% and intra-class correlation coefficient>0.90), with the lowest repeatability observed for the shortest efforts (10-s maximum mean power). These findings were confirmed separately for training sessions and competitions, albeit with lower repeatability (standard error of measurement<8% and intra-class correlation coefficient>0.80). The measure of durability appears therefore reliable, which might support its validity for monitoring field-based performance in professional cyclists.