Does anaerobic threshold correlate with maximal lactate steady-state?

The aim of this study was to compare the 'anaerobic threshold' (AnT) of subjects determined during a continuous 2-min incremental exercise test until exhaustion and the 'maximal lactate steady-state' (BLaSsmax) determined during prolonged exercise at constant loads corresponding to the subjects' AnT and/or 5-25% above and below it. Seventeen subjects performed an incremental exercise test and 1-5 prolonged exercise tests on a cycle ergometer until exhaustion at intervals of 1 week, and work rates, oxygen uptake (VO2) values and brachial venous blood lactate (BLa) levels were measured. It was proposed that when exercising at a constant workload below AnT, BLa would fall after having reached its peak; at the level of AnT, BLa reaches maximal steady-state (BLaSsmax); and above AnT, BLa increases continuously. Altogether, in 34 of 45 tests with a constant workload between 80 and 125% AnT, BLa values were as expected. In those cases in which BLaSsmax was reached, BLa increased on average by 3.8 mM from resting levels. This increase was 2.0 mM greater than that seen between resting levels and AnT during incremental exercise. There was no correlation between BLa values at BLaSsmax and at AnT, both when expressed as an increase in BLa (delta BLa) and absolute BLa concentration. Altogether, 81% of the variation in BLa concentration at BLaSsmax could be explained by the subjects' age, the percentage of slow-twitch fibres and BLa levels at rest. The AnT and BLaSsmax did not differ significantly, and these values were correlated (r = 0.83). Together, AnT and age accounted for 85% of the variation seen in BLaSsmax. The BLaSsmax did not correlate with AnT when fixed at a BLa concentration of 4 mM (AnT4mM). The three hypotheses tested in this study were confirmed, and the present results demonstrate that AnT correlates with BLaSsmax. The few exceptions to anticipated BLa kinetics were small in magnitude and could be explained by physiological variations.