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Journal of Exercise Nutrition & Biochemistry 2001;5(2):33-56.
Review : Effect of exercise and drug on prevention and treatment of osteoporosis
Abstract
Though skeletal muscle protein makes up more than 60% of whole body protein and protein metabolism in skeletal muscle, which accounts for more than 25% of the whole body protein turnover, it has received relatively little attention in comparison to carbohydrate and fat metabolism in the exercise science field. Among amino acids, the branched-chain amino acids(BCAA) taken up by the muscle, rather than the liver, to contribute to oxidative metabolism during endurance exercise. Moreover, since the oxidation of BCAA in muscles may exceed the catabolic capacity to increase BCAA availability, plasma BCAA levels may decline during endurance exercise. And also, an increase in FFA availability during endurance exercise alter the plasma ratio of free tryptophan to BCAA. It has been hypothesized that and increase in the plasma ratio of free tryptophan to BCAA concentration during endurance exercise is cause of central fatigue due to increased uptake of tryptophan in the brain and increased synthesis of serotonin. Based on these hypothesis, it has been suggested that supplementation of BCAA before endurance exercise may inhibite an increase in the plasma ratio of free tryptophan to BCAA concentration and improve endurance exercise performance. And also, another way to manipulate the plasma concentration of free tryptophan is carbohydrate feedings. However considerable controversy surround the relationship of the supplementation of BCAA and(or) carbohydrate to endurance exercise performance. Future study, therefore, is obviously required to verify the effects of hormones and secondary metabolites on central fatigue and endurance performance after BCAA supplementation. For objective study, more research must be conducted to investigate the effects of amount and time of BCAA supplementation, moreover exercise intensity and duration.


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