Adding more than one isolation exercise for the arm muscles, after doing compound exercises, does not lead to significantly more muscle growth.
Mechanism
Synthesis from 1 study
Your arm muscles only need so much work to grow as big as they can. Doing one good compound exercise already pushes them to their growth limit — adding more isolation moves doesn’t push them any further, because they can’t respond to more stimulus than that.
Most probable mechanism
When you do a compound exercise like a row or pull-up, your arm muscles are already being worked hard enough to trigger all the growth signals they can respond to. Adding extra isolation exercises doesn’t push them beyond that limit — it’s like turning up a faucet that’s already at max flow; more water won’t make the bucket fill faster.
Compound exercises generate sufficient mechanical tension and metabolic stress to maximally activate mTOR signaling pathways in muscle fibers.
Additional isolation exercises do not increase total mechanical load or time-under-tension beyond the threshold required to sustain maximal protein synthesis rates.
Muscle protein synthesis reaches a ceiling response after a certain volume of effective stimulation, beyond which no further hypertrophy occurs.
Evidence from Studies
Supporting (1)
Community contributions welcome
Small muscle mass exercise enhances muscular adaptations? Effects of unilateral and bilateral biceps curl on maximum strength and muscle size changes.
Contradicting (0)
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