Muscle Protein Synthesis: The 3g Leucine Trigger & MPS Timing
By Strength & Exercise Physiology Review Board•
Physiology & Training Takeaway
Maximizing anabolic signaling: reaching the 2.7–3.5g leucine threshold per meal, overcoming the muscle-full effect, and optimizing 4-meal daily protein distribution.
Muscle Protein Synthesis (MPS) operates as a binary switch. Reaching the threshold concentration of intracellular leucine activates the Sestrin2-GATOR2 nutrient sensing complex.
1. The Leucine Anabolic Threshold
The 3g Leucine Trigger: To maximize mTORC1 stimulation, each meal must supply roughly 3 grams of intact L-leucine (~25–40g of high-quality dairy, meat, or egg protein).
The Muscle-Full Effect: MPS remains elevated for 2.5 to 3 hours post-ingestion before returning to baseline, requiring spaced feedings every 3.5–5 hours.
Daily Target: Consuming 1.6 to 2.2 grams of total protein per kilogram of body weight (0.8–1.0g/lb) maximizes fractional synthetic rate in drug-free lifters.
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Strength & Exercise Physiology Review Board
Our editorial team includes CSCS certified strength and conditioning specialists, sports nutritionists, and biomechanists reviewing muscle protein synthesis trials, mTORC1 signaling pathways, and lifting torque mechanics.
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