Ferguson C, Whipp BJ, Cathcart AJ, Rossiter HB, Turner AP, Ward SA. Effects of prior very-heavy intensity exercise on indices of aerobic function and high-intensity exercise tolerance. J Appl Physiol 103: [812][813][814][815][816][817][818][819][820][821][822] 2007. First published May 31, 2007; doi:10.1152/japplphysiol.01410.2006.-A recent bout of high-intensity exercise can alter the balance of aerobic and anaerobic energy provision during subsequent exercise above the lactate threshold ( L). However, it remains uncertain whether such "priming" influences the tolerable duration of subsequent exercise through changes in the parameters of aerobic function [e.g., L, maximum oxygen uptake (V O2max)] and/or the hyperbolic power-duration (P-t) relationship [critical power (CP) and the curvature constant (WЈ)]. We therefore studied six men performing cycle ergometry to the limit of tolerance; gas exchange was measured breath-by-breath and arterialized capillary blood [lactate] was measured at designated intervals. On different days, each subject completed 1) an incremental test (15 W/min) for estimation of L and measurement of the functional gain (⌬V O2/ ⌬WR) and V O2peak and 2) four constant-load tests at different work rates (WR) for estimation of CP, WЈ, and V O2max. All tests were subsequently repeated with a preceding 6-min supra-CP priming bout and an intervening 2-min 20-W recovery. The hyperbolicity of the P-t relationship was retained postpriming, with no significant difference in CP (241 Ϯ 39 vs. 242 Ϯ 36 W, post-vs. prepriming), V O2max (3.97 Ϯ 0.34 vs. 3.93 Ϯ 0.38 l/min), ⌬V O2/⌬WR (10.7 Ϯ 0.3 vs. 11.1 Ϯ 0.4 ml ⅐ min Ϫ1 ⅐ W Ϫ1 ), or the fundamental V O2 time constant (25.6 Ϯ 3.5 vs. 28.3 Ϯ 5.4 s). WЈ (10.61 Ϯ 2.07 vs. 16.13 Ϯ 2.33 kJ) and the tolerable duration of supra-CP exercise (Ϫ33 Ϯ 11%) were each significantly reduced, despite a less-prominent V O2 slow component. These results suggest that, following supra-CP priming, there is either a reduced depletable energy resource or a residual fatiguemetabolite level that leads to the tolerable limit before this resource is fully depleted. power-duration relationship; WЈ; oxygen uptake kinetics; slow component; lactate threshold THE TOLERABLE DURATION of muscular exercise, such as cycling or running, is dependent on both the limit (i.e., V O 2max ) and the contour (i.e., V O 2 kinetics) of the oxygen uptake (V O 2 ) response profile. The phase 2 (or fundamental) V O 2 kinetics during constant-load cycle ergometer exercise have been shown to reflect those of muscle O 2 consumption [following a short, transit delay, i.e., phase 1 (3, 20)], with V O 2 attaining a steady state with first-order exponential kinetics. Moderateintensity work rates [i.e., below the lactate threshold ( L )] are highly sustainable, there being no sustained arterial lactate concentration ([L Ϫ ]a) increase (reviewed in Refs. 24, 55). For heavy-intensity work rates that lie between L and critical power [CP; i.e., the power asymptote of the power-duration (P-t) relationship], the emerg...