The Y-intercept of the maximal work-duration regression and field tests of anaerobic capacity in cyclists

The purpose of the present study was to provide initial data upon which field tests of anaerobic capacity for cyclists might be developed, by examining the relationships between the y-intercept of the maximal work-duration regression (Y-int) and cycle performance variables in fifteen well-trained male cyclists (mass = 73.3±8.6kg; VO₂peak = 4.93±0.70 I·min^-1). The Y-int was determined from three maximal supra-VO₂ peak cycle bouts varying in duration from 195 to 369 s. Each cyclist performed two performance tests: 1) an all-out cycle sprint over 1000m (AOS) during which the accumulated time over intervals of 125m (e.g., AOS125, AOS250, etc. was recorded; 2) a 2-by-2000m ride from which an 'anaerobic distance' (An(I)) was determined as the product of anaerobic speed (i.e. average speed during a second, maximal 2000m time-trial minus the average speed during a 20km time-trial) and time taken to complete the maximal 2000m ride. The frontal area (FA) of each cyclist and common values for air density, work efficiency and the drag coefficient were used to estimate the energy equivalent of An(I). The Y-int was 20.0±9.4kJ or 278±128 J·kg^-1. The Y-int (J·FA^-1) was correlated (p≤0.05) with AOS250 (r=-0.50), A0S375 (r=-0.53) and AOS625 (r=-0.50) which were 21.5±1.1 s, 30.1±1.3 s and 47.5±1.9 s long, respectively. The Y-int (kJ) was also correlated with A0S375 (r =-0.51), but Y-int (kJ) was not correlated with a performance variable lasting longer than ~ 30s. The energy equivalent of An(I) (91.5±26.0 kJ) was similar to the energy equivalent for Y-int (90.9±43 kJ), although these two variables were not significantly correlated. However, given the potential sources of variance in determining both of these variables, their quantitative similarity provides limited evidence supporting the use of An(I) to estimate anaerobic capacity. The results also support the use of an all-out sprint performance lasting between 20-30s to best reflect anaerobic work capacity in cyclists.