Muscle Protein Synthesis
Muscle protein synthesis (MPS) is the process by which the body builds new muscle protein, stimulated mainly by resistance training and protein intake.
Published by Repit Fitness · Last updated
Key facts
- The driver of muscle repair and growth.
- Triggered by training and dietary protein, especially leucine.
- Stays elevated for roughly 24–48 hours after training.
- Muscle grows when MPS outpaces muscle breakdown over time.
Your muscles are constantly being built up and broken down. Muscle protein synthesis is the 'building up' side, and muscle grows only when synthesis exceeds breakdown over the long run. Resistance training and eating protein are the two strongest levers for raising MPS.
Protein — and the amino acid leucine in particular — flips the switch that starts the process, while training amplifies and prolongs it for up to a day or two. This is why combining regular lifting with adequate, well-distributed protein is the foundation of building muscle.
Frequently asked questions
What stimulates muscle protein synthesis?
Resistance training and dietary protein are the main triggers. The amino acid leucine plays an outsized role in switching the process on.
How long is MPS elevated after training?
For trained individuals it stays elevated for roughly 24–48 hours, which is part of why training each muscle 2–3 times per week is effective.
This article is general information, not medical advice. Talk to a doctor or registered dietitian before making changes if you have a health condition, are pregnant or take medication.
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