For untrained young men, adding isolated arm exercises like bicep curls to a workout routine that already includes compound movements like bench presses and rows does not lead to bigger arm muscles...
Mechanism
Synthesis from 1 study
In untrained men, compound exercises like push-ups and pull-downs already push the arm muscles hard enough to trigger their full potential for growth and strength; adding arm curls doesn’t make them work any harder, so there’s no extra benefit (10.1139/apnm-2012-0176).
Most probable mechanism
When untrained men do compound exercises like push-ups and pull-downs, their arm muscles get stretched and pulled hard enough to trigger all the growth and strength signals they can handle; adding isolated arm curls doesn’t push those signals any higher, so the arms don’t get bigger or stronger than they already did from the compound moves alone (10.1139/apnm-2012-0176).
Multi-joint exercises generate sufficient mechanical tension and muscle fiber recruitment in the elbow flexors to maximally activate mTOR signaling and protein synthesis pathways, which drive hypertrophy and strength gains.
Adding single-joint exercises does not increase total mechanical load, muscle activation, or metabolic stress beyond the level achieved by multi-joint exercises alone, resulting in no further stimulation of muscle growth or neural adaptation.
Evidence from Studies
Supporting (1)
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Effect of adding single-joint exercises to a multi-joint exercise resistance-training program on strength and hypertrophy in untrained subjects.
Contradicting (0)
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