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.