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Fractional Synthesis Rate

Meaning

Fractional Synthesis Rate (FSR) is a quantitative physiological metric used to determine the proportion of a specific protein pool, such as muscle protein or collagen, that is newly synthesized over a defined period. Expressed as a percentage per day, FSR provides a dynamic measure of tissue turnover and anabolism. It is a precise indicator of the body’s capacity for tissue repair and growth, a critical aspect of hormonal health and longevity.