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

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 (V̇O(2max)), (t(lim) V̇O(2max)). Seven physical education students ran in an incremental test (3-min stages) to determine V̇O(2max) and the minimal velocity at which it was elicited (νV̇O(2max)). 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% νV̇O(2max) 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 V̇O(2max) in the 90% νV̇O(2max) test. All the subjects reached V̇O(2max) in the runs at 100% νV̇O(2max). All the subjects, except one, reached V̇O(2max) in the runs at 120%νV̇O(2max). Four subjects did not reach V̇O(2max) in the 140% νV̇O(2max) test. Time to achieve V̇O(2max) 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% νV̇O(2max) as determined in the previous incremental test. In conclusion, t(lim) V̇O(2max) depended on a balance between the time to attain V̇O(2max) and the time to exhaustion t(lim). The time to reach V̇O(2max) decreased as velocity increased. The t(lim) V̇O(2max) was a bi-phasic function of velocity, with a peak at 100% νV̇O(2max).