In young adults doing arm exercises for eight weeks, using momentum to lift weights does not lead to more or less muscle growth in the biceps and triceps than lifting with strict form, even though...
Mechanism
Synthesis from 1 study
Muscle growth happens when the muscle is pulled hard enough, not when it moves more weight. Swinging the weight doesn’t make the muscle work harder than lifting it slowly and controlled — so even though more total weight is moved, the muscle doesn’t grow any bigger.
Most probable mechanism
When lifting weights, muscle growth happens when the muscle fibers are stretched and pulled hard enough to trigger repair and thickening. Even when people swing the weight to lift more total weight, the actual force on the muscle fibers doesn’t go beyond a certain point — so adding extra movement doesn’t make the muscle grow more.
Muscle fibers experience mechanical tension during concentric and eccentric phases of contraction, activating mechanosensitive pathways that initiate signaling for protein synthesis and muscle remodeling.
External momentum increases total volume load but does not increase peak or time-under-tension mechanical tension beyond the threshold required to maximally stimulate hypertrophic signaling in single-joint movements.
Muscle growth reaches a plateau when mechanical tension exceeds a minimal effective dose, and additional load from ancillary movement does not further activate mTOR or other downstream anabolic pathways.
Evidence from Studies
Supporting (1)
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Do Cheaters Prosper? Effect of Externally Supplied Momentum During Resistance Training on Measures of Upper Body Muscle Hypertrophy
Contradicting (0)
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Gold Standard Evidence Needed
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