Oxygen kinetics and modelling of time to exhaustion whilst running at various velocities at maximal oxygen uptake

Abstract

The purpose of this study was to characterise the relationship between running velocity and the time for which a subject can run at maximal oxygen uptake (V˙O_{2 max}), (t _lim V˙O_{2 max}). Seven physical education students ran in an incremental test (3-min stages) to determine V˙O_{2 max} and the minimal velocity at which it was elicited (νV˙O_{2 max}). They then performed four all-out running tests on a 200-m indoor track every 2 days in random order. The mean times to exhaustion t _lim at 90%, 100%, 120% and 140% νV˙O_{2 max} were 13 min 22 s (SD 4 min 30 s), 5 min 47 s (SD 1 min 50 s), 2 min 11 s (SD 38 s) and 1 min 12 s (SD 18 s), respectively. Five subjects did not reach V˙O_{2 max} in the 90% νV˙O_{2 max} test. All the subjects reached V˙O_{2 max} in the runs at 100% νV˙O_{2 max}. All the subjects, except one, reached V˙O_{2 max} in the runs at 120%νV˙O_{2 max}. Four subjects did not reach V˙O_{2 max} in the 140% νV˙O_{2 max} test. Time to achieve V˙O_{2 max} was always about 50% of the time to exhaustion irrespective of the intensity. The time to exhaustion-velocity relationship was better fitted by a 3- than by a 2-parameter critical power model for running at 90%, 100%, 120%, 140% νV˙O_{2 max} as determined in the previous incremental test. In conclusion, t _lim V˙O_{2 max} depended on a balance between the time to attain V˙O_{2 max} and the time to exhaustion t _lim. The time to reach V˙O_{2 max} decreased as velocity increased. The t _lim V˙O_{2 max} was a bi-phasic function of velocity, with a peak at 100% νV˙O_{2 max}.