VO2max May Not Be Reached during Exercise to Exhaustion above Critical Power

SAWYER, B. J., R. H. MORTON, C. J. WOMACK, and G. A. GAESSER. VO2max May Not Be Reached during Exercise to Exhaustion above Critical Power. Med. Sci. Sports Exerc., Vol. 44, No. 8, pp. 1533-1538, 2012. Purpose: This study was designed to determine whether VO2 reaches a maximum, equivalent to that attained in an incremental exercise test to exhaustion, during "submaximal'' fatigue-inducing constant-power exercise bouts above critical power (CP). Methods: Nine males (age = 24.6 +/- 3.6 yr, height = 182.8 +/- 6.9 cm, weight = 77.8 +/- 12.1 kg) and four females (age = 29.0 +/- 7.3 yr, height = 170.8 +/- 3.2 cm, weight = 61.8 +/- 8.2 kg) underwent an incremental VO2max test (IET) on a cycle ergometer, followed by four or five randomly assigned constant-power exercise bouts to exhaustion, on separate days. The CP for each subject was estimated using linear and nonlinear regression. Results: IET VO2max averaged 3.55 +/- 0.92 L.min(-1) (RER = 1.21 +/- 0.05, HR = 186 +/- 10 bpm, 96.1% +/- 6.3% of age-predicted maximum). Mean peak VO2 (range = 3.32 +/- 0.88 to 3.54 +/- 0.91 L.min(-1)) during the three highest constant-power bouts (two of which were 53 to 82 W less than peak power output attained during IET) was not significantly different from IET VO2max. Eleven of 13 subjects exceeded their IET VO2max during at least one of the constant-power exercise bouts. However, peak VO2 (3.11 +/- 0.79 L.min(-1)) during the lowest constant-power exercise bout, which ranged from 10 to 36 W above CP estimated with a two-parameter nonlinear model, was significantly lower than IET VO2max (88.2% +/- 9.4% of IET VO2max). Conclusions: At power outputs above CP, VO2 does not necessarily increase to maximum during constant-power exercise to exhaustion. In addition, the highest VO2 values measured during a traditional VO2 "max'' test (i.e., IET) may not reflect the highest attainable VO2 despite VO2max criteria being met.