Muscle protein synthesisMPS

Muscle protein synthesis (MPS) is the process by which the body builds new muscle protein. Muscle is in constant turnover between synthesis and breakdown; net growth happens when synthesis outpaces breakdown over time.

It matters because resistance training and eating protein both raise MPS, and the balance of synthesis over breakdown across days and weeks is what determines whether you gain muscle.

In practice, spreading adequate protein across the day and training each muscle regularly keeps MPS elevated and supports growth.