After six weeks of resistance training with the same total workload, the thigh muscle (vastus lateralis) showed a small increase in size, while the upper arm muscle (triceps brachii) did not change,...
Mechanism
Synthesis from 1 study
When you lift until you slow down, some muscles get much more tired than others, and that extra fatigue makes certain fibers work harder and grow slightly bigger — but only if the muscle is built to fatigue that way during that movement. The front thigh muscle does this during squats, but the back...
Most probable mechanism
When someone lifts weights until their movement slows down a lot, some muscles get more tired than others, which causes certain muscle fibers to work harder and build up more protein, making them slightly bigger — but this only happens in muscles that naturally fatigue more during those movements, like the front thigh, not the back of the upper arm.
Higher velocity loss during resistance exercise indicates greater neuromuscular fatigue, leading to increased recruitment of high-threshold motor units.
Recruitment of high-threshold Type II muscle fibers elevates mechanical tension and metabolic stress within the muscle, particularly in muscles with a higher proportion of these fibers and greater fatigue sensitivity during dynamic contractions.
Metabolic stress, including lactate accumulation, intracellular acidosis, and cell swelling, activates signaling pathways such as mTORC1, CaMKII, and sarcolipin-related cascades that promote muscle protein synthesis.
Sustained protein synthesis exceeds degradation, resulting in net accretion of myofibrillar proteins and increased muscle thickness, but only in muscles where the combination of movement mechanics and fiber type allows sufficient metabolic stress to accumulate under velocity loss conditions.
Evidence from Studies
Supporting (1)
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Effects of Low- Versus High-Velocity-Loss Thresholds With Similar Training Volume on Maximal Strength and Hypertrophy in Highly Trained Individuals.
Contradicting (0)
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