The adaptations of skeletal muscle with exercise training involve:
Increased amounts of enzymes involved in beta oxidation, Krebs cycle metabolism and the electron transport chain;
Improved fatty acid transport through the sarcolemma, the plasma membrane of the muscle fibre;
Improved transport of fatty acids within the muscle cell by the action of carnitine and carnitine transferase;
Proliferation of capillaries, represented by an increase in numbers and in their density.
Effects of endurance training
Improved ability to obtain ATP from oxidative phosphorylation;
Increased size and number of mitochondria;
Less lactic acid produced per given amount of exercise;
Increased myoglobin content;
Increased intramuscular triglyceride content;
Increased lipoprotein lipase;
Increased proportion of energy derived from fat, less from carbohydrate; Lower rate of glycogen depletion during exercise; Improved efficiency in extracting oxygen from blood; Decreased number of type lib fibres; increased number of type Ila fibres.
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