Effects of priming exercise intensity on the dynamic linearity of the pulmonary VO(2) response during heavy exercise

Prior heavy-intensity exercise facilitates the pulmonary oxygen uptake ( VO(2)) response during subsequent exercise, such that its kinetics returns towards first-order. To better understand this "priming" phenomenon, we investigated the effect of priming exercise, over a range of intensities, on the VO(2) response to heavy-intensity cycle ergometry at a work rate of Delta50% [halfway between lactate threshold (LT) and VO(2max)]. Eight subjects performed two consecutive 6-min bouts separated by 6 min at 20 W. The first bout was each of: no warm-up control (CON), sub-lactate threshold (LT) at 80% of LT, and three supra-LT conditions (Delta20%, Delta40%, and Delta60%). The VO(2) response during the subsequent bout was evaluated using the "effective" time constant (tau'), and the VO(2) difference between minutes 3 and 6 (Delta VO(2(6-3))). The goodness-of-fit, indicative of "first-order" kinetics, was determined by the residual profile, and the mean square of errors (MSEr). The heart rate and blood lactate concentration ([La]r) just prior to the second bout were also measured. Compared with CON, tau' and Delta VO(2(6-3)) were significantly reduced following all supra-LT priming bouts, while the goodness-of-fit was significantly improved following Delta40% exercise. Delta VO(2(6-3)) and [La]r were negatively correlated ( P<0.05), unlike HR. In conclusion, prior exercise just above, but not below, LT facilitated the VO(2) response in a threshold-like manner. Supra-LT priming exercise influenced the VO(2) response allowing it to return to within as little as 12% from first-order (compared to approximately 50% in CON). The associated increases in circulating lactate and/or related factors seem to be centrally involved in this phenomenon.