The Muscle Protein Synthetic Response to Meal Ingestion Following Resistance-Type Exercise
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The Muscle Protein Synthetic Response to Meal Ingestion Following Resistance‑Type Exercise Jorn Trommelen1 · Milan W. Betz1 · Luc J. C. van Loon1
© The Author(s) 2019
Abstract Protein ingestion following resistance-type exercise stimulates muscle protein synthesis rates and consequently enhances the skeletal muscle adaptive response to prolonged training. Ingestion of ~ 20 g of quickly digestible protein isolate optimizes muscle protein synthesis rates during the first few hours of post-exercise recovery. However, the majority of daily protein intake is consumed as slower digestible, nutrient-rich, whole-food protein sources as part of mixed meals. Therefore, the muscle protein synthetic response to the ingestion of protein supplements and typical foods or mixed meals may differ substantially. In addition, the muscle protein synthetic response to feeding is not only determined by acute nutrient intake but is also likely modulated by habitual energy and nutrient intake and nondietary factors such as habitual physical activity, body composition, age, and/or sex. Therefore, nutritional recommendations to maximize the muscle protein synthetic response to exercise depend on the type of meal (e.g., protein supplements vs. mixed meals) and the time until the next feeding opportunity (e.g., feeding before overnight sleep) and, therefore, need to be personalized to the individual athlete.
Key Points
1 Introduction
Ingestion of 20 g of isolated, quickly digestible protein results in a near-maximal muscle protein synthetic response at rest and post-exercise, with a 10–20% further increase when the ingested amount is doubled to 40 g.
While muscle mass is remarkably constant in healthy adults, it is a highly adaptive organ capable of changing in size and/or function. Even when muscle mass is constant, muscle tissue is constantly turning over, i.e., the rates at which muscle proteins are synthesized and broken down are in balance. This turnover allows muscle tissue to remodel, e.g., replacing damaged proteins with new proteins or changing the composition of muscle proteins to adapt to challenges such as exercise. An imbalance between protein synthesis and protein breakdown rates in skeletal muscle results in either a net gain (synthesis > breakdown) or net loss (breakdown > synthesis) in muscle mass. A single session of exercise stimulates muscle protein synthesis (MPS) rates and, to a lesser extent, muscle protein breakdown rates [1, 2]. However, muscle protein net balance will remain negative in the absence of food intake [2]. Protein ingestion stimulates MPS and inhibits muscle protein breakdown rates, resulting in net muscle protein accretion during the acute stages of post-exercise recovery [3]. Therefore, post-exercise protein ingestion is widely applied as a strategy to augment post-exercise MPS rates and, as such, to facilitate the skeletal muscle adaptive response to prolonged exercise training.
The ingestion of ≥ 40 g of slow digestible protein is recommended to maximize muscle protein synthesis
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