After six weeks of intense weight training, the proportions of two key muscle proteins—myosin heavy chain and actin—remain unchanged in the thigh muscles of trained young men.
Mechanism
Synthesis from 1 study
When trained people lift light weights for many reps, their muscles grow by adding more of the non-pulling stuff inside them—like energy tools and fluids—not by changing how much of the actual pulling proteins are there. That’s why the muscle gets bigger but the mix of key contractile proteins...
Most probable mechanism
When someone does lots of repetitions with lighter weights, their muscle cells make more of the non-contracting parts inside them, like energy-making tools and fluids, but they don't change how much of the actual pulling proteins (myosin and actin) are there. So the muscle gets bigger, but the ratio of these key contractile proteins stays the same.
High-volume resistance training increases intracellular calcium flux during repeated muscle contractions
Elevated intracellular calcium transiently activates MAPK signaling pathways
Activated MAPK signaling preferentially upregulates translation of non-myofibrillar proteins (e.g., metabolic and sarcoplasmic enzymes)
Accumulation of non-myofibrillar proteins increases muscle volume without changing the relative abundance of myosin heavy chain or actin
Evidence from Studies
Supporting (1)
Community contributions welcome
Effects of High-Volume Versus High-Load Resistance Training on Skeletal Muscle Growth and Molecular Adaptations
Contradicting (0)
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