In people who regularly lift weights, training the side shoulder muscle with dumbbells or cables for 8 weeks results in the same small to moderate increase in muscle thickness, regardless of whether...
Mechanism
Synthesis from 1 study
The side shoulder muscle grows the same amount whether the weight feels heavier at the start or the end of the movement, because the full stretch and pull over the same motion is enough to make the muscle build more protein. The total tension matters more than when it peaks.
Most probable mechanism
When the side shoulder muscle is stretched and contracted through the same range of motion, the force applied to the muscle fibers activates signals that tell the muscle to build more protein, leading to thicker fibers. This happens whether the resistance is heavier at the start or at the end of the movement, because the total amount of stretch and tension over the full motion is enough to trigger growth.
The lateral deltoid muscle is stretched to a length where it enters the descending limb of the length-tension relationship during shoulder abduction.
Mechanical tension applied to the muscle fibers during contraction activates intracellular signaling pathways, including mTOR and MAPK, which increase the rate of muscle protein synthesis.
Muscle protein synthesis exceeds proteolytic breakdown, resulting in net accumulation of myofibrillar proteins within muscle fibers.
The accumulation of myofibrillar proteins increases muscle fiber cross-sectional area, which is measured as increased muscle thickness.
Evidence from Studies
Supporting (1)
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Dumbbell versus cable lateral raises for lateral deltoid hypertrophy: an experimental study
Contradicting (0)
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