Increases in muscle MCT are associated with reductions in muscle lactate after a single exercise session in humans

To investigate the effects of a single session of prolonged cycle exercise [60% peak O2 uptake (V˙o 2 peak) for 5–6 h] on metabolic adaptations in working vastus lateralis muscle, nine untrained males (peak O2 uptake = 47.2 ± 1.1 ml · kg−1 · min−1, means ± SE) were examined before (Pre) and at 2 (Post-2), 4 (Post-4), and 6 (Post-6) days after the training session. On the basis of 15 min of cycle exercise at 59% V˙o 2 peak, it was found that training reduced (P < 0.05) exercise muscle lactate (mM) at Post-2 (6.65 ± 0.69), Post-4 (7.74 ± 0.63), and Post-6 (7.78 ± 1.2) compared with Pre (10.9 ± 1.3). No effect of training was observed on exercise ATP, phosphocreatine, and glycogen levels. After the single session of training, plasma volumes were elevated (P < 0.05) at Post-2 (6.7 ± 1.7%), Post-4 (5.86 ± 1.9), and Post-6 (5.13 ± 2.5). The single exercise session also resulted in elevations (P< 0.05) in the monocarboxylate transporters MCT1 and MCT4 throughout the 6 days after exercise. Although epinephrine an...