About 19% of older adults who don't gain muscle from resistance training still don't gain muscle even when they do more sets, suggesting their bodies may have biological limits that training volume...
Mechanism
Synthesis from 1 study
When older adults do more sets of resistance training, the extra tension usually turns on a muscle-building switch called mTOR-p70S6K, helping most people grow muscle — but about 1 in 5 still don’t grow, even with more sets, suggesting their muscles have a biological limit in how well this switch...
Most probable mechanism
When older adults do more sets of resistance training, the increased tension on their muscles turns on a molecular switch called mTOR, which then activates p70S6K to help build more muscle proteins — this is why most nonresponders start growing muscle with higher volume, but some still don't, possibly because their muscles can't turn on this switch well enough even with more training (10.1152/japplphysiol.00670.2023).
Mechanical tension from increased resistance training volume activates mechanosensors in skeletal muscle fibers, initiating intracellular signaling (10.1152/japplphysiol.00670.2023)
Mechanotransduction signals converge on the mTORC1 complex, promoting its activation in response to higher training volume (10.1152/japplphysiol.00670.2023)
Activated mTORC1 phosphorylates p70S6K, enhancing its activity and driving ribosomal biogenesis and translation initiation (10.1152/japplphysiol.00670.2023)
Increased translational capacity elevates myofibrillar protein synthesis rates, enabling net muscle protein accretion over time (10.1152/japplphysiol.00670.2023)
Persistent failure to activate this pathway in approximately 19% of older adults despite increased volume suggests intrinsic limitations in mechanotransduction or mTOR signaling efficiency, preventing hypertrophy regardless of training dose (10.1152/japplphysiol.00670.2023)
Evidence from Studies
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Contradicting (1)
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Higher resistance training volume offsets muscle hypertrophy non-responsiveness in older individuals.
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