Computational modeling suggests that muscle growth takes weeks to become visible because ribosomes, which are needed to build muscle proteins, accumulate slowly due to physical obstruction by...
Mechanism
Synthesis from 1 study
Muscles don’t grow right away after lifting weights because it takes time for the cell to make enough protein-building machines. The pulling from exercise turns on a signal that starts making more machines, but they get stuck in the crowded muscle fibers—so it takes weeks for enough to pile up...
Most probable mechanism
When you lift weights, the stretching of muscle fibers pulls on a special protein called titin, which acts like a molecular switch. This switch turns on a signal that tells the cell to make more protein-making machines called ribosomes. But these machines can't move easily through the crowded space inside muscle fibers, so it takes weeks for enough of them to build up before the muscle can start growing visibly.
Mechanical tension during resistance exercise stretches titin, applying force to its kinase domain at the sarcomere M-band
Force induces a conformational change in titin kinase, transitioning it from a closed to an open state, enabling ATP-dependent phosphorylation
Phosphorylated titin kinase recruits nbr1 to form a signaling complex that activates SRF transcription factor
SRF activation increases transcriptional programs that drive ribosome biogenesis
Newly synthesized ribosomes diffuse slowly through the dense myofilament lattice due to steric hindrance
Ribosome density increases over weeks until sufficient to sustain elevated myofibrillar protein synthesis
Increased protein synthesis of sarcomeric components leads to gradual increase in myofibrillar cross-sectional area
Evidence from Studies
Supporting (1)
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Why exercise builds muscles: titin mechanosensing controls skeletal muscle growth under load
Contradicting (0)
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