Physical training in man. Skeletal muscle metabolism in relation to muscle morphology and running ability.
The metabolic and morphologic adaptation to physical training in skeletal muscle tissue of eleven middle-aged, physically untrained men was studied. Muscle biopsies were taken from the vastus lateralis before, after 8 weeks and after 6 months of physical training for analysis of metabolic and morphologic variables. Glucose tolerance test indicated increased insulin sensitivity after 6 months of physical training. The activities of glycogen phosphorylase, hexokinase and glucose-6-P-dehydrogenase were increased but other enzymes involved in glycogen turnover and glycolysis were unchanged after 6 months of physical traning. The activities of citrate synthase and cytochrome-c-oxidase, representing the oxidative capacity were significantly increased already after 8 weeks of physical training. The incorporation rate of palmitate-carbon into CO2 and triglycerides increased, and the incorporation rate of leucine-carbon into CO2 decreased with 6 months of physical training. The fiber diameter of both Type 1- and Type 2-fibers increased, while the mitochondrial volume increased predominantly in Type 2-fibers. Significant correlations were found between metabolic, physiologic and morphologic variables before and after physical training. The results indicate an increased oxidative capacity, mainly located to Type 2-fibers, and an increased utilization of fatty acids in response to this type of physical training.
D002331:Carnitine / Q000378:metabolism; D002950:Citrate (si)-Synthase / Q000378:metabolism; D005227:Fatty Acids / Q000378:metabolism; D005951:Glucose Tolerance Test; D006003:Glycogen / Q000378:metabolism; D006019:Glycolysis; D006801:Humans; D050356:Lipid Metabolism; D008297:Male; D008854:Microscopy, Electron; D008875:Middle Aged; D008931:Mitochondria, Muscle / Q000648:ultrastructure; D009124:Muscle Proteins / Q000378:metabolism; D009132:Muscles / Q000378:metabolism* / Q000648:ultrastructure; D010084:Oxidation-Reduction; D010806:Physical Education and Training; D010809:Physical Fitness
D005227:Fatty Acids; D009124:Muscle Proteins; D006003:Glycogen; D002950:Citrate (si)-Synthase; D002331:Carnitine