Effects of high-intensity training on muscle lactate transporters and postexercise recovery of muscle lactate and hydrogen ions in women

Bishop D, Edge J, Thomas C, Mercier J. Effects of high-intensity training on muscle lactate transporters and postexercise recovery of muscle lactate and hydrogen ions in women. Am J Physiol Regul Integr Comp Physiol 295: R1991-R1998, 2008. First published October 1, 2008; doi:10.1152/ajpregu.00863.2007. -The purpose of this study was to investigate the effects of high-intensity interval training ( 3 days/wk for 5 wk), provoking large changes in muscle lactate and pH, on changes in intracellular buffer capacity (beta m(in) (vitro)), monocarboxylate transporters (MCTs), and the decrease in muscle lactate and hydrogen ions (H+) after exercise in women. Before and after training, biopsies of the vastus lateralis were obtained at rest and immediately after and 60 s after 45 s of exercise at 190% of maximal O-2 uptake. Muscle samples were analyzed for ATP, phosphocreatine (PCr), lactate, and H+; MCT1 and MCT4 relative abundance and beta m(in) (vitro) were also determined in resting muscle only. Training provoked a large decrease in postexercise muscle pH ( pH 6.81). After training, there was a significant decrease in beta m(in) (vitro) (-11%) and no significant change in relative abundance of MCT1 ( 96 +/- 12%) or MCT4 (120 +/- 21%). During the 60-s recovery after exercise, training was associated with no change in the decrease in muscle lactate, a significantly smaller decrease in muscle H+, and increased PCr resynthesis. These results suggest that increases in beta m(in) (vitro) and MCT relative abundance are not linked to the degree of muscle lactate and H+ accumulation during training. Furthermore, training that is very intense may actually lead to decreases in beta m(in) (vitro). The smaller postexercise decrease in muscle H after training is a further novel finding and suggests that training that results in a decrease in H+ accumulation and an increase in PCr resynthesis can actually reduce the decrease in muscle H+ during the recovery from supramaximal exercise.