Reference
Resistance Training
**Resistance training** is physical exercise in which skeletal muscle contracts against an external load — free weights, machines, resistance bands, or body weight — to produce mechanical tension that, over repeated sessions, increases muscle size and strength.
How it stimulates muscle
Resistance training and dietary protein intake are the two primary non-genetic factors that stimulate muscle protein synthesis (MPS). A single bout of resistance exercise triggers intracellular signaling through the mTOR pathway: acute exercise produces rapid phosphorylation of downstream proteins such as p70S6K and 4E-BP1, measurable within roughly an hour of the working set. A key step following an anabolic stimulus is the translocation of mTORC1 to the lysosome and to peripheral regions of the muscle fiber.
These responses are not fixed. Chronic resistance training alters the mTOR signaling response to a single exercise bout, indicating that repeated training adaptations modulate the pathway’s acute sensitivity (Journal of Applied Physiology, 2013, PMID:23372143).
Why protein matters alongside it
Resistance training and protein feeding act synergistically; protein consumed without the mechanical stimulus does not, on its own, produce muscle growth. In a randomized controlled trial, 30 g of whey protein after resistance exercise significantly raised myofibrillar protein synthesis versus placebo (0.041 vs 0.032 %·h⁻¹), an effect tied to the postprandial rise in plasma leucine and essential amino acids (Med Sci Sports Exerc, 2023, PMID:37202878).
Protein quality and source both influence the size of that response. Potato protein isolate has been shown to stimulate muscle protein synthesis at rest and with resistance exercise in young women (Nutrients, 2020, PMID:32349353), indicating anabolic properties comparable to those of well-studied animal proteins. Practical intake targets are covered in our guide to protein for athletes.
Aging and sarcopenia
Resistance training is a central countermeasure to sarcopenia, the progressive loss of muscle mass and function with age. Aging is characterized by a blunted MPS response to protein intake, a condition termed anabolic resistance (PubMed PMID:23558692). The synergistic effect of resistance exercise and protein ingestion on muscle anabolism is also delayed in older adults compared with the young, with the peak synthetic response occurring later after combined exercise and amino acid ingestion (Journal of Applied Physiology, 2008, PMID:18323467).
Because of this reduced sensitivity, older adults generally require higher protein intakes — on the order of 1.0–1.5 g/kg/day — alongside regular resistance training to maintain muscle. The exercise stimulus and adequate protein work together; neither fully substitutes for the other.
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