Significance of time to exhaustion during exercise at the velocity associated with VO2max.

In theory, time to exhaustion at the velocity associated with VO2max (tLIM at vVO2max) together with the anaerobic threshold (AT) should provide information about the anaerobic capacity of an individual. The primary purpose of this study was to test that hypothesis, using oxygen deficit as a criterion for anaerobic capacity. A second purpose was to identify factors that might explain the large inter-individual variability reported in tLIM at vVO2max. Subjects were 13 female track athletes who performed incremental treadmill tests to determine VO2max and AT and constant velocity tests at vVO2max to determine tLIM and oxygen deficit. Correlations between oxygen deficit and tLIM at vVO2max and [(tLIM at vVO2max).(VO2max-AT)], a compound variable derived based on the critical power concept, were 0.51 (p < 0.05, one-tailed) and 0.67 (p < 0.01). To identify factors related to the inter-individual variability in tLIM at vVO2max, correlations between tLIM and AT, oxygen deficit, and [oxygen deficit/(VO2max-AT)] were calculated. Intra-individual differences in AT explained 44% of the variability in tLIM at vVO2max, oxygen deficit explained 26% of the variance, and the compound variable explained only 36%. It was concluded that (a) alone, or in combination with AT, tLIM at vVO2max cannot be used to estimate anaerobic capacity and (b) factors other than anaerobic capacity and AT contribute to the relatively large intra-individual variability in tLIM at vVO2max (CV = 21%). Determinants of tLIM at vVO2max must be elucidated if this measure is to be of use to sport scientists.