Divergent response of metabolite transport proteins in human skeletal muscle after sprint interval training and detraining.
Burgomaster KA, Cermak NM, Phillips SM, Benton CR, Bonen A, Gibala MJ.
Skeletal muscle primarily relies on carbohydrate (CHO) for energy provision during high-intensity exercise. We hypothesized that sprint interval training (SIT), or repeated sessions of high-intensity exercise, would induce rapid changes in transport proteins associated with CHO metabolism, whereas changes in skeletal muscle fatty acid transporters would occur more slowly. Eight active men (22 +/- 1 yr; peak oxygen uptake = 50 +/- 2 ml.kg(-1).min(-1)) performed 4-6 x 30 s all-out cycling efforts with 4-min recovery, 3 days/wk for 6 wk. Needle muscle biopsy samples (vastus lateralis) were obtained before training (Pre), after 1 and 6 wk of SIT, and after 1 and 6 wk of detraining. Muscle oxidative capacity, as reflected by the protein content of cytochrome c oxidase subunit 4 (COX4), increased by approximately 35% after 1 wk of SIT and remained higher compared with Pre, even after 6 wk of detraining (P < 0.05). Muscle GLUT4 content increased after 1 wk of SIT and remained approximately 20% higher compared with baseline during detraining (P < 0.05). The monocarboxylate tranporter (MCT) 4 was higher after 1 and 6 wk of SIT compared with Pre, whereas MCT1 increased after 6 wk of training and remained higher after 1 wk of detraining (P < 0.05). There was no effect of training or detraining on the muscle content of fatty acid translocase (FAT/CD36) or plasma membrane associated fatty acid binding protein (FABPpm) (P > 0.05). We conclude that short-term SIT induces rapid increases in skeletal muscle oxidative capacity but has divergent effects on proteins associated with glucose, lactate, and fatty acid transport.