Muscle protein synthesis is the process by which the body builds new muscle protein from amino acids. It is in constant interplay with the breakdown of muscle protein, known as protein breakdown. If synthesis outweighs breakdown over a longer period, this can show up in the long term as a gain in muscle mass, although many factors such as training, nutrition and recovery work together. Sufficient sleep and recovery between training sessions are also considered important conditions for this process.
Muscle protein synthesis is triggered, among other things, by strength training and by protein intake, in particular by the essential amino acid leucine. In sports science, values of around 1.2 to 2.0 g of protein per kilogram of body weight per day, spread across several meals, are often cited for strength training, as a guide and not as a fixed recommendation from this site. Without a regular training stimulus, the effect of a higher protein intake on muscle protein synthesis remains limited.
How individual portions of protein can be sensibly spread across the day is described in the entry Protein distribution across the day, and more on the role of leucine is explained in the entry Leucine. An overview of building muscle is offered by the guide Protein for muscle building.
