Abstract
The aim of this study was to investigate the physiological demands of Supercross BMX
in elite athletes. Firstly athletes underwent an incremental cycling test to determine
maximal oxygen uptake (VO2max) and power at ventilatory thresholds. In a second phase, athletes performed alone
a simulated competition, consisting of 6 cycling races separated by 30 min of passive
recovery on an actual BMX track. Oxygen uptake, blood lactate, anion gap and base
excess (BE) were measured. Results indicated that a simulated BMX performed by elite
athletes induces a high solicitation of both aerobic (mean peak VO2 (VO2peak): 94.3±1.2% VO2max) and anaerobic glycolysis (mean blood lactate: 14.5±4. 5 mmol.L − 1) during every race. Furthermore, the repetition of the 6 cycling races separated
by 30 min of recovery led to a significant impairment of the acid-base balance from
the third to the sixth race (mean decrease in BE: − 18.8±7.5%, p<0.05). A significant
relationship was found between the decrease in BE and VO2peak (r= − 0.73, p<0.05), indicating that VO2peak could explain for 54% of the variation in BMX performance. These results suggest
that both oxygen-dependent and –independent fuel substrate pathways are important
determinants of BMX performance.
Key words
bicycle motocross - elite athletes - intermittent sprints - buffering capacity - aerobic
demand - anaerobic glycolysis