Velocity-specific fatigue: Quantifying fatigue during variable velocity cycling

GARDNER, A. S., D. T. MARTIN, D. G. JENKINS, I. DYER, J. VAN EIDEN, M. BARRAS, and J. C. MARTIN. Velocity-Specific Fatigue: Quantifying Fatigue during Variable Velocity Cycling. Med. Sci. Sports Exerc., Vol. 41, No. 4, pp. 904-911, 2009. Previous investigators have quantified fatigue during short maximal cycling trials (similar to 30 s) by calculating a fatigue index. Other investigators have reported a curvilinear power-pedaling rate relationship during short fatigue-free maximal cycling trials (<6 s). During maximal trials, pedaling rates may change with fatigue. Quantification of fatigue using fatigue index is therefore complicated by the power-pedaling rate relationship. Purpose: The purpose of this study was to quantify fatigue while accounting for the effects of pedaling rate on power. Methods: Power and pedaling rate were recorded during Union Cycliste Internationale sanctioned 200-m time trials by eight male (height = 181.5 +/- 4.3 cm, mass = 87.0 +/- 8.0 kg) world-class sprint cyclists with SRM power meters and fixed-gear track bicycles. Data from the initial portion of maximal acceleration were used to establish maximal power-pedaling rate relationships. Fatigue was quantified three ways: 1) traditional fatigue index, 2) fatigue index modified to account for the power-pedaling rate relationship (net fatigue index). and 3) work deficit, the difference between actual work done and work that might have been accomplished without fatigue. Results: Fatigue index (55.4% +/- 6.4%) was significantly greater than net fatigue index (41.0% +/- 7.9% P < 0.001), indicating that the power-pedaling rate relationship accounted for 14.3% +/- 7% of the traditional fatigue index value. Work deficit (23.3% +/- 6%) was significantly less than either measure of fatigue (P < 0.001). Conclusion: Net fatigue index and work deficit account for the power-pedaling rate relation and therefore more precisely quantify fatigue during variable velocity cycling. These measures can be used to compare fatigue during different fatigue protocols, including world-class sprint cycling competition. Precise quantification of fatigue during elite cycling competition may improve evaluation of training status, gear ratio selection, and fatigue resistance.