Last updated: 3 October 2026
Reviewed by Jordan Morley, FA Level 2 Football Coach
Muscle protein synthesis (MPS) is the anabolic process that repairs and grows muscle fibres after resistance training. MPS is stimulated by two primary factors: mechanical loading from exercise (particularly resistance training) and amino acid availability (particularly leucine). Protein intake of 20-40g per meal maximally stimulates MPS; spreading protein evenly across 3-4 meals per day produces greater total MPS than eating the same total in 1-2 meals. MPS remains elevated for 24-48 hours after resistance exercise. Anabolic window research shows meal timing is less critical than once believed — total daily protein matters most.
- Stimulated by resistance training + protein
- Leucine is the key trigger amino acid
- 20-40g per meal maximally stimulates MPS
- Elevated for 24-48h after resistance training
In practice
Muscle protein synthesis — the process of building new muscle protein structures — is stimulated by both resistance training and adequate protein (particularly leucine-rich) intake, and the two work together: training alone without sufficient protein limits the amount of actual muscle growth achievable, while protein intake without resistance training provides little stimulus for the body to use that protein for muscle building specifically.
FAQ
What triggers muscle protein synthesis?
Resistance training (mechanical tension on muscle fibres) and adequate protein intake (particularly amino acids like leucine) both stimulate muscle protein synthesis, and the two work synergistically together.
Does protein synthesis stay elevated for a long time after training?
Muscle protein synthesis is typically elevated for roughly 24-48 hours following a resistance training session, which is part of why spreading protein intake across the day (not just immediately post-workout) supports ongoing muscle building.