Effect of Protocol on Determination of Velocity at V̇O₂ max and on its Time to Exhaustion

Abstract

The velocity associated with the achievement of V̇O₂ max during an incremental treadmill test (ν V̇O₂ max) has been reported to be an indicator of performance in middle distance running events. Previous study has shown the reproducibility of the time to exhaustion (time limit: tlim) at ν V̇O₂ max performed by well-trained males in the same condition at one week of interval (Billat et al., 1994b). It is essential in studies involving tlim at ν V̇O₂ max that the ν V̇O₂ max be precisely determined, or else the measured tlim will be meaningless. The purpose of this study was to examine the influence of the stage duration and velocity incrementation on the velocity at V̇O₂ max and, consequently, on the two times to exhaustion (tlim) associated with the two ν V̇O₂ max generated by the two protocols. ν V̇O₂ max was determined in 15 trained male endurance athletes as the lowest speed at which V̇O₂ max was attained in speed-incremented 0%-slope treadmill tests. For one test, increments were 1.0 km·h^−l and stages were 2 min in duration; for the other test, increments were 0.5 km·h^−l and stages were 1 min in duration. Results of paired means t-tests revealed no difference in ν V̇O₂ max obtained using the two protocols. ν V̇O₂ max was 20.7 ± 1.0 km. h^−l with the 1.0 km·h^−l × 2 min protocol and 20.8 ± 0.9 km·h^−l with the 0.5 km·h^−l × 1 min protocol. In addition, V̇O₂, V̇CO₂, V̇E, V̇E/V̇O₂ and respiratory exchange ratio at the submaximal intensities that were common to both protocols (e.g., 17.0 km·h^−l, 18.0 km·h^−l, 19.0 km·h^−l, 20.0 km·h^−l) did not differ. Times to exhaustion at the two ν V̇O₂ max demonstrated a high degree of inter-individual variability (coefficients of variation were 35 % and 45 %) but did not differ (345 ± 120 s versus 373 ± 169 s). These results demonstrated that small changes in protocol have no significant impact on the value of ν V̇O₂ max and in consequence on tlim ν V̇O₂ max.