When the total mechanical workload is the same, training muscles while they are stretched does not consistently lead to more muscle growth than training them while they are shortened.
Mechanism
Synthesis from 2 studies
Muscles grow when they're worked hard, no matter if they're stretched or shortened, as long as the total effort is the same. This is because the body uses two different ways to signal growth — one from chemical buildup and one from physical force — but both end up turning on the same...
Most probable mechanism
When muscles are worked under load, whether stretched or shortened, the body responds by activating pathways that tell muscle fibers to build more protein. This happens through either the buildup of metabolic byproducts like lactic acid and swelling, or through the physical force of tension on the fibers — both of which trigger the same molecular signals to increase protein production. Since both pathways lead to the same outcome, muscle growth ends up being similar no matter how stretched or shortened the muscle is during exercise, as long as the total effort is the same.
Resistance exercise under load, regardless of muscle length, induces intramuscular metabolite accumulation and/or mechanical tension on myofibers
Metabolite accumulation (e.g., lactate, H+, inorganic phosphate) and/or mechanical tension activate intracellular sensors that stimulate mTORC1 and MAPK signaling pathways
Activated mTORC1 signaling increases ribosomal biogenesis and translation initiation, elevating the rate of myofibrillar protein synthesis
Satellite cells are recruited and fuse with existing muscle fibers to provide additional nuclei, supporting sustained protein synthesis and structural growth
Net protein accretion occurs across muscle regions, resulting in hypertrophy that is not preferentially enhanced by longer muscle lengths under matched total mechanical load
Evidence from Studies
Supporting (2)
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The effects of shoulder extension angle on elbow flexor hypertrophy in the cable curl exercise
Similar Regional Hypertrophy of the Elbow Flexor Muscles in Response to Low-Load Training With Vascular Occlusion at Short Versus Long Muscle Lengths
Contradicting (0)
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