Determination of the velocity associated with VO2max.

Purpose: The theoretical velocity associated with VO2max (vVO2max) defined by Daniels (1985) is extrapolated from the submaximal VO2-velocity relationship. VO2 is generally determined by assuming that the aerobic response reacts like a linear first-order system at the beginning of square-wave exercise with a steady-state reached by the 4th minute. However, at supra-ventilatory threshold work rates, the steady state in VO2 is delayed or not attained.

Methods: The present study was carried out to compare three values for vVO2max determined with Daniels' method, but with VO2 either measured at the 4th minute (vVO2max4), the 6th minute (vVO2max6), or after the attainment of the true steady-state (vVO2maxSS). The metabolic response during square-wave exercise at each of the three vVO2max were also assessed.

Results: These velocities were significantly different (P < 0.05), but vVOmaxSS and vVO2max6 were highly correlated (r = 0.98; P < 0.05). Blood lactate concentrations measured after exercise at velocities very close to the three vVO2max were similar and the end-exercise VO2 were not different from VO2max, but the time required to elicit 95% VO2max during these three square-wave tests were significantly different.

Conclusion: Therefore, when vVO2max is determined by extrapolation from the submaximal VO2-velocity relationships, submaximal VO2 should be measured beyond the 6th minute of square-wave exercise (at least if it takes 30 s to reach the desired velocity) to ensure that all vVO2max reported in future studies describe a similar quantitative index.