Total Anaerobic Work in Trained Cyclists

Abstract

BACKGROUND: Previous studies have suggested that the total amount of anaerobic work that can be performed during exhausting work bouts is constant for work tasks of 2–5 min duration. These studies were based on constant intensity exercise to fatigue, rather than on time trials (TT) with subjects free to regulate momentary power output. The aim of the present study was to quantify and compare the contribution of the anaerobic energy system in 750, 1500, 2500 and 4000-m cycling TT. METHODS: Well-trained male cyclists (n=10) performed 4 randomly ordered TT. The duration of the TT was short enough so that exercise intensity remained >VO2max throughout the trials. The contributions of the energy systems were calculated from measurements of mechanical power and VO2. Gross efficiency was measured at 150W on the same day, and was assumed to be the same during the TT. RESULTS: The TT of 750, 1500, 2500 and 4000 m were completed in (mean + sd) 57.2 + 1.7, 116.3 + 1.7, 198.5 + 4.9 and 325.3 + 9.4 s, respectively. The total work, attributable to anaerobic sources, accomplished in the four distances was 22.7 + 2.7, 26.9 + 2.4, 29.8 + 4.7 and 33.9 + 7.0 kJ, respectively. Anaerobically attributable work for 750-m was lower (p<0.05) than in all other trial distances; the two middle distances (1500-m and 2500-m) did not differ; and the 4000-m was larger than all other TT distances. CONCLUSIONS: It can be concluded that: 1) The anaerobically attributable work during high intensity TT is dependent on distance, increasing with increasing TT distance; which is contrary to the hypothesis that anaerobic capacity is constant during exhausting exercise bouts of 2–5 min duration, 2) The effect of assuming a constant efficiency based on submaximal trials remains problematic with this technique.