Lactate transport studied in sarcolemmal giant vesicles from human muscle biopsies: relation to training status.

The present study examined sarcolemmal lactate transport capacity in humans of widely different training status. Muscle biopsies were obtained from m. vastus lateralis in 39 subjects divided into untrained (n = 13), trained (n = 7), and athlete [sprint runners (n = 2), endurance runners (n = 5), triathletes (n = 3), and road (n = 6) and track (n = 3) bicyclists] groups. From the biopsy sample giant vesicles were produced with collagenase treatment to determine the sarcolemmal lactate transport capacity, and histochemical analyses were made. The athletes had a higher capacity to transport lactate than the untrained and trained subjects (P < 0.01). Within the group of athletes, the bicyclists had a higher lactate transport capacity than the runners (P < 0.05), whereas there was no difference among trained subjects, runners, and triathletes. The lactate transport capacity was related to the occurrence of type I muscle fibers (r = 0.48, P < 0.01). The present results suggest that the capacity to transport lactate is higher in athletes than in untrained and less trained subjects. It might indicate that lactate transport capacity in human skeletal muscle can be changed by a high volume of training including frequent high-intensity sessions. In addition, sarcolemmal lactate transport capacity appears to be related to the fiber type distribution of a muscle.