VO2max, protocol duration, and the VO2 plateau.

PURPOSE The purpose of this study was to compare VO2max, VO2-time slopes at the end of the protocol (last 30 s), and the presence of a VO2 plateau (VO2-time slope < 0.05 L.min(-1) during the last 30 s) across four protocol durations (5, 8, 12, and 16 min) during incremental cycling exercise to VO2max. METHODS Eight male (23.8 +/- 3.2 yr) and eight female (26.0 +/- 8.9 yr) subjects of moderate to high fitness levels participated in the study. RESULTS VO2max was significantly higher in men than in women for each protocol duration, with main effect means of 4.23 versus 2.84 L.min(-1), respectively. For women, VO2max did not differ between any protocol duration. For men, VO2max for the 8-min protocol (4.44 +/- 0.39 L.min(-1)) was significantly higher than for all other protocol durations. Analysis of covariance, using the highest VO2max as the covariate, removed all protocol-duration significance for men. The VO2 slope for the final 30 s of each test was significantly lower for the 16-min protocol compared with the 5-min protocol, for both men and women. The ventilation threshold across four protocols was similar, at approximately 76% of VO2max for both men and women. CONCLUSIONS The protocol duration of tests to VO2max should be between 8 and 10 min for healthy, moderately to highly trained subjects.