Rate of decline in blood lactate after cycling exercise in endurance-trained and -untrained subjects

The purpose of this study was to compare the rate of decline in blood lactate (La) levels in nine trained men [maximal O₂ consumption (V̇O(2 max)) 65.5 ± 3.3 ml · kg^-1 · min^-1] and eight untrained men (V̇O(2 max) 42.2 ± 2.8 ml · kg^-1 · min^-1) during passive recovery from a 3-min exercise bout. Trained and untrained subjects cycled at 85 and 80% V̇O(2 max), respectively, to produce similar peak blood La concentrations. Twenty samples of arterialized venous blood were drawn from a heated hand vein during 60 min of recovery and analyzed in an automated La analyzer. The data were then fitted to a biexponential function, which closely described the observed data (r = 0.97-0.98). There was no difference in the coefficient expressing the rate of decline in blood La for trained and untrained groups (0.0587 ± 0.0111 vs. 0.0579 ± 0.0100, respectively). However, trained subjects demonstrated a faster time-to-peak La (P = 0.01), indicative of a faster efflux of La from muscle to blood. Thus the rate of decline in blood La after exercise does not appear to be affected by training. The faster decline previously reported for trained subjects may be due to the use of a linear rather than a biexponential curve fit.