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Fig. 1 | Journal of the International Society of Sports Nutrition

Fig. 1

From: Branched-chain amino acids and muscle protein synthesis in humans: myth or reality?

Fig. 1

Schematic representation of the recycling of essential amino acids (EAAs) from muscle protein breakdown into muscle protein synthesis in the post-absorptive state. Arbitrary units are used for simplicity and are based on measured rates of each pathway in post-absorptive human subjects [10]. a Normal circumstance in the post-absorptive state. Approximately 70% of EAAs from muscle protein breakdown are recycled into protein synthesis [10]. There is a net efflux of approximately 85% of EAAs released from protein breakdown, which can either be taken up and incorporated into protein in other tissues or oxidize. About 15% of EAAs from protein breakdown are partially oxidized in muscle and unavailable for protein synthesis. The figures for outward flux and intracellular oxidation of EAAs are averages, since some EAAs, such as phenylalanine, are not oxidized at all in muscle. b Representation of a 50% increase in efficiency of recycling of EAAs from muscle protein breakdown into protein synthesis. In this example there would be an increase in synthesis from 70 to 80 units, or 20%. Protein synthesis can never exceed protein breakdown in the post-absorptive state, since protein breakdown is the only source of EAAs

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