INCREASED CLEARANCE OF LACTATE AFTER SHORT-TERM TRAINING IN MEN

A short-term training model previously shown to result in a tighter me tabolic control in working muscle in the absence of an increase in mit ochondrial potential was used to examine changes in lactate turnover. Lactate flux was studied before and after 10 days of cycle training [2 h/day at 59% maximal oxygen consumption (Vover dotO(2max))] in untrai ned men [Vover dotO(2max) = max 45.5 +/- 2.4 (SE) ml . kg(-1). min(-1) ). A primed constant infusion of L-[1-C-13]lactate was used to examine lactate kinetics during a prolonged exercise protocol (90 min at 59% Vover dotO(2max)). Rate of appearance of lactate increased with exerci se (P < 0.01), both pretraining (rest = 30.3 +/- 4.9 ml . kg(-1). min( -1), exercise = 115 +/- 14 ml . kg(-1). min(-1)) and posttraining (res t 28.4 +/- 4.7 ml . kg(-1). min(-1), exercise = 112 +/- 13 ml . kg(-1) . min(-1)). Despite a lower blood lactate concentration (P < 0.05) dur ing exercise after training, there was no difference in the rate of ap pearance of lactate. Training increased (P < 0.05) the metabolic clear ance rate of lactate during exercise from 36.8 +/- 4.8 to 51.4 +/- 6.8 ml . kg(-1). min(-1). These findings indicate that at least part of t he lower exercising blood lactate observed after training is due to an increase in metabolic clearance rate. In addition, the lower intramus cular lactate levels suggest a decreased recruitment of glycolysis par ticularly early in exercise.