Workout Completed — Breakdown Outpaces Synthesis
Training briefly tips the balance toward muscle protein breakdown.
- +15%: MPB vs MPS shift (breakdown over synthesis)
- 0.0 h: Elapsed time (immediately post-set)
- 2-3×: Cortisol spike (transient rise)
- ~40%: Glycogen depleted (type II fibers)
Why breakdown rises
Mechanical stress briefly raises muscle protein breakdown.
Not actual muscle loss
This shift is normal turnover, not tissue damage.
Where the myth begins
This moment is the origin of the "anabolic window" idea.
Traditional "Anabolic Window" Belief
Bodybuilding lore demanded protein within a narrow post-workout minute count.
- 30-60 min: Believed window (popular claim)
- 1990s-2000s: Origin era (early sports nutrition)
- Heavy: Supplement marketing (shake timing urgency)
- Few: Strict-window studies (mostly small, flawed)
Where the myth started
Early studies used fasted, glycogen-depleted subjects.
Marketing amplified it
Supplement brands sold urgency around shake timing.
Evidence did not scale
Later meta-analyses found a much smaller effect.
Extended Sensitivity Period — Hours, Not Minutes
Muscle remains receptive to protein for several hours after training.
- 4-6 h: Real sensitivity window (elevated MPS response)
- up to 24 h: Detectable elevation (some MPS studies)
- Extends it: Pre-workout meal effect (amino acids already circulating)
- ~3 h: Sensitivity half-life (gradual decay, not a cliff)
Sensitivity decays gradually
Muscle protein sensitivity fades slowly, not sharply.
Pre-workout meals matter
A meal beforehand extends the effective window further.
No sharp cutoff exists
No study shows synthesis collapsing at minute 61.
Daily Total Intake Accumulates
Every meal across the day adds to cumulative muscle protein synthesis.
- 3-5: Meals per day (typical) (protein-containing meals)
- ~0.4 g/kg: Per-meal MPS ceiling (roughly, per dose)
- 1.6-2.2 g/kg: Daily need (trained) (bodyweight)
- Small: Distribution effect size (vs total intake effect)
Meals stack synthesis
Each protein meal triggers its own MPS pulse.
Distribution has minor effect
Even spacing helps slightly, not dramatically.
Total sets the ceiling
Cumulative daily grams cap how much muscle can grow.
Total Protein Dominates Over Timing
Research consistently ranks total daily protein above timing precision.
- Small: Timing effect size (confounded by total intake)
- Large: Total intake effect size (primary, robust driver)
- Hit daily total: Practical takeaway (timing is secondary)
- Total > timing: ISSN 2017 position stand (expert consensus)
Meta-analysis finding
Controlling for total protein erased the timing effect.
ISSN position stand
Total daily protein ranked as the primary driver.
Practical guidance
Hit your daily target; exact timing stays flexible.