Among older adults who do resistance training, some people gain strength even if their muscles don't get bigger, and this pattern occurs in about 38% of cases, showing that improvements in muscle...
Mechanism
Synthesis from 1 study
When older adults lift heavier or do more sets, some grow bigger muscles because their bodies turn on a protein-building switch (mTOR-p70S6K), but others get stronger without growing bigger because their nerves learn to activate muscles more efficiently — this is shown in...
Most probable mechanism
When older adults do more sets of resistance training, the extra tension on their muscles turns on a molecular switch (mTOR-p70S6K) that helps build more muscle proteins — but not everyone’s muscles respond the same way to this signal. Some people’s muscles grow bigger with more sets, while others get stronger without much muscle growth, because strength can improve through better nerve signaling even when muscle size doesn’t change much. This is shown in the study 10.1152/japplphysiol.00670.2023, where people who didn’t gain muscle from light training still got stronger when they did more sets.
Higher resistance training volume increases mechanical tension on skeletal muscle fibers, activating mechanosensitive pathways that converge on the mTORC1 complex, as inferred from volume-dependent increases in p70S6K phosphorylation and myofibrillar protein synthesis in older adults.
Activated mTORC1 triggers phosphorylation of p70S6K, enhancing ribosomal biogenesis and translation initiation to increase myofibrillar protein synthesis, a process directly linked to resistance training volume in older adults.
Net myofibrillar protein synthesis over time leads to muscle fiber hypertrophy and increased cross-sectional area, which occurs in some older individuals only when training volume is increased, indicating anabolic resistance in others.
Strength gains independent of hypertrophy occur through neural adaptations — such as improved motor unit recruitment and firing frequency — that are not dependent on mTOR-p70S6K-driven protein synthesis, allowing individuals to become stronger without measurable muscle growth.
Evidence from Studies
Supporting (1)
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Higher resistance training volume offsets muscle hypertrophy non-responsiveness in older individuals.
Contradicting (0)
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