Exercise tolerance through severe and extreme intensity domains

The power‐duration relationship accurately predicts exercise tolerance for constant power exercise performed in the severe intensity domain. However, the accuracy of the prediction of time to task failure (T (lim)) is currently unclear for work rates (WR) above severe intensities; that is, within the extreme intensity domain (T (lim) < 2 min). We hypothesized that T (lim) would be shorter for WRs within the extreme intensity domain than predicted from the linear 1/time relationship of the severe intensity domain which would suggest mechanisms limiting exercise are different between intensity domains. Six men completed 7 knee‐extension tests. T (lim) of extreme intensity exercise (60%, 70%, 80%, and 90% 1RM; T (lim) < 2 min) were compared to the predicted T (lim) from the slope of the S1–S3 (T (lim) ≥ 2–15 min) regression. Twitch force (Q (tw)) and maximal voluntary contraction (MVC) were measured on the right vastus lateralis before and after each test. T (lim) at 70–90% 1RM were shorter than the T (lim) predicted by the severe domain 1/time model (P < 0.05); however, T (lim) at 60% 1RM was not different than the predicted severe T (lim), suggesting the mechanisms limiting extreme exercise manifest ≥60% 1RM. A significant linear relationship for 60–90% 1RM was observed which suggested a curvature constant unique to the extreme domain ([Formula: see text]) that was smaller than the W ′ of the severe domain (1.5 ± 0.6 vs. 5.9 ± 1.5 kJ, P < 0.001). Q (tw) and MVC were significantly decreased following severe exercise, however, Q (tw) and MVC were not significantly decreased following 80% and 90% 1RM, giving evidence that mechanisms causing task failure were recovered by the time post‐exercise measurements were made (~90 sec).