Divergent response of metabolite transport proteins in human skeletal muscle after sprint interval training and detraining

1 Exercise Metabolism Research Group, Department of Kinesiology, McMaster University, Hamilton, Ontario; 2 Department of Kinesiology, University of Waterloo, Waterloo, Ontario; and 3 Department of Human Health & Nutritional Sciences, University of Guelph, Guelph, Ontario, Canada Submitted 17 July 2006 ; accepted in final form 12 February 2007 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 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 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. GLUT4; monocarboxylate transporters; fatty acid translocase; plasma membrane fatty acid binding protein Address for reprint requests and other correspondence: M. J. Gibala, Dept. of Kinesiology, McMaster Univ., Hamilton, Ontario L8S 4K1 Canada (e-mail: gibalam{at}mcmaster.ca )