Does resistance exercise increase muscle protein remodeling and make delayed protein intake postpone amino-acid-supported muscle gain?

Resistance exercise promotes muscle-protein turnover, a relevant adaptation for preserving or increasing muscle mass in older adults. In a 74-year-old woman, the acute response is influenced by training dose, fasting status, and the amount and quality of protein subsequently consumed.

Clinical and physiological evidence

• Human tracer studies in healthy older women show higher myofibrillar muscle-protein synthesis (MPS) in an exercised than rested leg. With post-exercise feeding, MPS rose 71% with a leucine-matched milk-protein supplement and 47% with whey; integrated MPS over six days was 9% higher in the exercised limb.
• Exercise-induced remodeling includes both synthesis and breakdown. During fasted exercise, protein breakdown may also rise, so higher MPS alone does not ensure positive net muscle-protein balance.
• After overnight fasting in postmenopausal women, exercise alone increased MPS during 0–2 hours, whereas post-exercise whey increased MPS during the later 2–4-hour period. Thus, delaying protein-containing food delays the point at which dietary amino acids can contribute to net gain.

Mechanism and practical meaning

• Protein must be consumed, digested, and absorbed before circulating amino acids can support post-exercise accretion. Resistance exercise also sensitizes muscle to protein feeding for many hours, rather than only immediately after the session.
• Accordingly, a delay prolongs the acute interval before food-derived amino acids support net muscle gain—especially after fasted training—but does not demonstrate that missing an immediate post-exercise meal compromises long-term hypertrophy, strength, or function.
• Protein dose and quality remain important. Older adults may need roughly 20–40 g of high-quality protein per serving, with higher amounts sometimes needed to maximize MPS.

Bottom line

• The claim is supported: resistance exercise increases muscle-protein remodeling, and postponing protein intake postpones acute amino-acid-supported net muscle gain. This is not evidence for a narrow mandatory “anabolic window”; adequate protein across the day and the surrounding meals remain central.