Endurance Exercise

Endurance exercise increases the ability of skeletal muscle and fat oxidation due to that it increases the mitochondrial density, oxygen delivery to muscle and the activities of the enzymes involved in oxidation (Melanson et al., 2009). The skeletal muscle type I (slow/oxidative) and type II (fast/glycolytic) display differences on the contraction of metabolism and fatigue. Type I muscle fibres have a tremendous capacity for oxidative metabolism, resulting from the significant number of capillaries and Krebs cycle enzymes, which are involved in fatty acid oxidation (Taylor and Bachman, 1999). Type IIa fibres hold the intermediate level of oxidative capacity, which usually overlaps with type I fibres. Type IIb fibres are the almost exclusive reliance on fuel and sugar, glucose and glycogen (Taylor and Bachman, 1999). Specifically, intramyocellular triacylglycerol, lipoprotein-derived triacylglycerol and plasma free fatty acids are proposed to be the source of fat oxidized by type I fibres (Wang et al., 2004). In other words, type I muscle fibres distribution contribute significantly to lipid oxidation during low-intensity exercise. …show more content…
Maximal fat oxidation is high in female compared to male due to the dissimilarities in levels of circulating catecholamine and hormones, or more oxidative muscle fiber type distribution (Turpeinen et al., 2006). The subjects who have a high amount of type I muscle fibres showed a tendency toward more active lipid oxidation at basal state and during endurance exercise in comparison to the subjects who have a low number of type I muscle fibers (Melanson et al., 2009). Especially, some research has indicated that obese subjects have less type I muscle fibers than lean subjects. Also, obesity has a tendency to reduce capacity for fat oxidation due to the inactive mitochondrial enzymes. (Wade et al.,