Randomized Trialmoderate evidence
Progesterone does not modulate myofibrillar protein synthesis at rest or following acute resistance exercise in premenopausal females.
The Journal of physiology·October 23, 2026·PMID 42924924
Why it mattersMenstrual cycle phase-based training and nutrition advice often assumes progesterone is catabolic to muscle, but direct mechanistic evidence in premenopausal females has been lacking. This study directly tests that assumption and finds no effect of acute progesterone elevation on muscle protein synthesis, challenging the rationale for cycle-synced training protocols.
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