Effects of prior very-heavy intensity exercise on indices of aerobic function and high-intensity exercise tolerance

A recent bout of high-intensity exercise can alter the balance of aerobic and anaerobic energy provision during subsequent exercise above the lactate threshold (θL). However, it remains uncertain whether such “priming” influences the tolerable duration of subsequent exercise through changes in the parameters of aerobic function [e.g., θL, maximum oxygen uptake (V̇o2max)] and/or the hyperbolic power-duration (P-t) relationship [critical power (CP) and the curvature constant (W′)]. 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 θL and measurement of the functional gain (ΔV̇o2/ΔWR) and V̇o2peak and 2) four constant-load tests at different work rates (WR) for estimation of CP, W′, and V̇o2max. 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 ± 39 vs. 242 ± 36 W, post- vs. prepriming), V̇o2max (3.97 ± 0.34 vs. 3.93 ± 0.38 l/min), ΔV̇o2/ΔWR (10.7 ± 0.3 vs. 11.1 ± 0.4 ml·min−1·W−1), or the fundamental V̇o2 time constant (25.6 ± 3.5 vs. 28.3 ± 5.4 s). W′ (10.61 ± 2.07 vs. 16.13 ± 2.33 kJ) and the tolerable duration of supra-CP exercise (−33 ± 11%) were each significantly reduced, despite a less-prominent V̇o2 slow component. These results suggest that, following supra-CP priming, there is either a reduced depletable energy resource or a residual fatigue-metabolite level that leads to the tolerable limit before this resource is fully depleted.