The Influence of Exercise Duration at V̇O2 max on the Offtransient Pulmonary Oxygen Uptake Phase During High Intensity Running Activity

Abstract

The purpose of this study was to examine the influence of time run at maximal oxygen uptake (V̇O2 max) on the offtransient pulmonary oxygen uptake phase after supra-lactate threshold runs. We hypothesised: 1) that among the velocities eliciting V̇O2 max there is a velocity threshold from which there is a slow component in the V̇O2-off transient, and 2) that at this velocity the longer the duration of this time at V̇O2 max (associated with an accumulated oxygen kinetics since V̇O2 can not overlap V̇O2 max), the longer is the offtransient phase of oxygen uptake kinetics. Nine long-distance runners performed five maximal tests on a synthetic track (400 m) while breathing through the COSMED K4b2 portable, telemetric metabolic analyser: i) an incremental test which determined V̇O2 max, the minimal velocity associated with V̇O2 max (μV̇O2 max) and the velocity at the lactate threshold (vLT), ii) and in a random order, four supra-lactate threshold runs performed until exhaustion at vLT + 25, 50, 75 and 100% of the difference between vLT and μV̇O2 max (vΔ25, vΔ50, vΔ75, vΔ100). At vΔ25, vΔ50 (= 91.0 ± 0.9% μV̇O2 max) and vΔ75, an asymmetry was found between the V̇O2 on (double exponential) and off-transient (mono exponential) phases. Only at vΔ75 there was at positive relationship between the time run at V̇O2 max (%tlimtot) and the V̇O2 recovery time constant (Z = 1.8, P = 0.05). In conclusion, this study showed that among the velocities eliciting V̇O2 max, vΔ75 is the velocity at which the longer the duration of the time at V̇O2 max, the longer is the off-transient phase of oxygen uptake kinetics. It may be possible that at vΔ50 there is not an accumulated oxygen deficit during the plateau of V̇O2 at O 2 max and that the duration of the time at V̇O2 max during the exhaustive runs at vΔ100, could be too short to induce an accumulating oxygen deficit affecting the oxygen recovery.