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 +/- 8.6 kg; VO2peak = 4.93 +/- 0.70 l.min-1). The Y-int was determined from three maximal supra-VO2peak cycle bouts varying in duration from 195 to 369 s. Each cyclist performed two performance tests: 1) an all-out cycle sprint over 1000 m (AOS) during which the accumulated time over intervals of 125 m (e.g., AOS125, AOS250, etc. was recorded; 2) a 2-by-2000 m ride from which an "anaerobic distance" (Anl) was determined as the product of anaerobic speed (i.e. average speed during a second, maximal 2000 m time-trial minus the average speed during a 20 km time-trial) and time taken to complete the maximal 2000 m 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 Anl. The Y-int was 20.0 +/- 9.4 kJ or 278 +/- 128 J.kg-1. The Y-int (J.FA-1) was correlated (p < or = 0.05) with AOS250 (r = -0.50), AOS375 (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 AOS375 (r = -0.51), but Y-int (kJ) was not correlated with a performance variable lasting longer than approximately 30 s. The energy equivalent of Anl (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 Anl to estimate anaerobic capacity. The results also support the use of an all-out sprint performance lasting between 20-30 s to best reflect anaerobic work capacity in cyclists.