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Muscle Protein Synthesis

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Muscle Protein Synthesis (MPS)

The biological process by which the body repairs and builds muscle fibers after training, using dietary protein as the raw material, the core process behind muscle growth.

Definition

Muscle protein synthesis is the biological process by which your body uses amino acids from dietary protein to repair and build new muscle fibers, primarily in response to resistance training. It's the direct mechanism behind muscle growth, training creates the mechanical stimulus, and adequate protein intake supplies the raw material the repair process actually requires.

Without sufficient protein, the body can't fully capitalize on the training stimulus, no matter how effectively progressive overload is applied. The Protein Calculator estimates how much daily protein supports this process based on body weight and training level.

Formula

There's no single formula, but a commonly used daily protein target for muscle building is:

Daily Protein Target = Body Weight (kg) × 1.6 to 2.2 grams

Worked Example

A 75 kg individual training with resistance exercise regularly:

  • Lower end target: 75 × 1.6 = 120 grams/day
  • Upper end target: 75 × 2.2 = 165 grams/day

Spreading this across 3-4 meals, roughly 30-40 grams per meal, tends to support a more consistent muscle protein synthesis response than concentrating it all into one large meal.

Key Things to Know

  • There's a per-meal ceiling to how much protein triggers synthesis. Consuming 100 grams in one sitting doesn't produce a proportionally larger response than 40 grams, spreading intake across the day is generally more effective.
  • Resistance training is what elevates the synthesis response above baseline. Protein alone, without a training stimulus, mostly supports maintenance rather than driving new muscle growth.
  • The "anabolic window" is wider than once believed. Total daily protein intake matters more than eating within a narrow post-workout timeframe, though having protein within a few hours of training still helps.
  • Older adults often need more protein per meal to get the same effect. Anabolic resistance means aging muscles respond less efficiently to a given protein dose, requiring a higher intake to trigger a comparable synthesis response.
  • Protein quality affects the response, not just quantity. Complete proteins containing all essential amino acids, especially leucine, trigger synthesis more effectively than incomplete protein sources eaten alone.

Related Calculators

Protein Calculator →Calculate your daily protein target in grams from body weight and goal, using evidence-based g/kg ranges for muscle building, fat loss, and general fitness.

Related Terms

Progressive OverloadProgressive Overload

Frequently Asked Questions

How much protein do I actually need to maximize muscle protein synthesis?
Research generally supports around 1.6-2.2 grams of protein per kilogram of body weight daily for people strength training, higher than the general population's needs. The [Protein Calculator](/protein-calculator/) can estimate a target based on your weight and activity level.
Does eating more protein than needed build muscle faster?
No, muscle protein synthesis has a practical ceiling per meal and per day, excess protein beyond what your body can use for repair and growth gets used for energy or stored, not converted into additional muscle.
Is protein timing around workouts actually important?
It matters less than total daily intake, but isn't irrelevant, consuming protein within a few hours of training helps keep the synthesis response elevated, though the old idea of a narrow 30-minute 'anabolic window' has been largely debunked.
Can muscle protein synthesis happen without exercise?
Yes, at a low baseline level, protein synthesis occurs continuously for normal tissue maintenance, but resistance training significantly amplifies the response specifically in the muscles that were trained.
Why do older adults need more protein for the same muscle-building effect?
Aging is associated with anabolic resistance, a reduced sensitivity to protein's muscle-building signal, meaning older adults often need higher protein intake per meal to trigger the same level of synthesis response as a younger person.