Effects of training on lactate kinetics parameters and their influence on short high-intensity exercise performance

The purpose of the present study was to relate the training-induced alterations in lactate kinetics parameters to the concomitant changes in time to exhaustion (T-lim) at a work rate corresponding to maximal oxygen uptake (Pa-peak). Eight subjects performed before and after training i) an incremental exercise up to exhaustion to determine Pa-peak, ii) a 5-min 90% Pa-peak exercise followed by a 90-min passive recovery to determine an individual blood lactate recovery curve fitted to the bi-exponential time function: La(t) = La(0) + A(1)(1-e(-gamma 1-t)) + A(2) (1-e(-gamma 2.t)), and iii) a time to exhaustion at Pa-peak to determine Tlim. A biopsy of the vastus lateralis muscle was made before and after training. The training programme consisted in pedalling on a cycle ergometer 2 h a day, 6 days a week, for 4 weeks. Training-induced increases (p < 0.05) in Pa-peak, muscle capillary density, citrate synthase activity, gamma(2) that denotes the lactate removal ability (from 0.0547 +/- 0.0038 to 0.0822 +/- 0.0071 min(-1)) and T-lim (from 299 +/- 23 to 486 +/- 63 s), decreases (p < 0.05) in activities of lactate dehydrogenase (LDH) and muscle type of LDH, the phosphofructokinase/citrate synthase activities ratio and the estimated net amount of lactate released (NALR) during exercise recovery (from 66.5 +/- 8.6 to 47.2 +/- 11.1 mmol) were also observed. The improvement of Tlim with training was related to the increase in 72 (r = 0.74, p = 0.0367) and to the decrease in NALR (r = 0.77, p = 0.0250). These results suggest that the post-training greater ability to remove lactate from the organism and reduced muscle lactate accumulation during exercise account for the concomitant improvement of the time to exhaustion during high-intensity exercise performed at the same relative work rate.