Time required for the restoration of normal heavy exercise V̇o2 kinetics following prior heavy exercise

Abstract

Prior heavy exercise markedly alters the O₂ uptake (V̇o₂) response to subsequent heavy exercise. However, the time required for V̇o₂ to return to its normal profile following prior heavy exercise is not known. Therefore, we examined the V̇o₂ responses to repeated bouts of heavy exercise separated by five different recovery durations. On separate occasions, nine male subjects completed two 6-min bouts of heavy cycle exercise separated by 10, 20, 30, 45, or 60 min of passive recovery. The second-by-second V̇o₂ responses were modeled using nonlinear regression. Prior heavy exercise had no effect on the primary V̇o₂ time constant (from 25.9 ± 4.7 s to 23.9 ± 8.8 s after 10 min of recovery; P = 0.338), but it increased the primary V̇o₂ amplitude (from 2.42 ± 0.39 to 2.53 ± 0.41 l/min after 10 min of recovery; P = 0.001) and reduced the V̇o₂ slow component (from 0.44 ± 0.13 to 0.21 ± 0.12 l/min after 10 min of recovery; P < 0.001). The increased primary amplitude was also evident after 20–45 min, but not after 60 min, of recovery. The increase in the primary V̇o₂ amplitude was accompanied by an increased baseline blood lactate concentration (to 5.1 ± 1.0 mM after 10 min of recovery; P < 0.001). Baseline blood lactate concentration was still elevated after 20–60 min of recovery. The priming effect of prior heavy exercise on the V̇o₂ response persists for at least 45 min, although the mechanism underpinning the effect remains obscure.