In untrained young women, resistance training that focuses on the beginning part of the movement causes more muscle growth in the lower part of the biceps compared to training that focuses on the end part of the movement.

We analyzed the available evidence and found that training the biceps in the initial range of motion may lead to more muscle growth in the lower part of the muscle compared to training in the final range. This conclusion is based on one assertion involving untrained young women, which reported greater hypertrophy in the distal region of the biceps when the training emphasized the beginning of the movement [1]. No studies or assertions in our review contradicted this finding. The evidence we’ve reviewed so far is limited to a single group — untrained women — and does not include men, trained individuals, or other muscle groups. We also don’t have data on how long the training lasted, what loads were used, or whether the results apply to other parts of the biceps. Because of this, we can’t say whether this pattern holds for everyone or if it’s specific to beginners or women. What we’ve found so far suggests that where you focus your effort during a movement might influence where the muscle grows, at least in some people under certain conditions. But without more studies, we don’t know how strong or consistent this effect is. If you’re new to lifting and want to target the lower part of your biceps, focusing on the first half of curls — like the stretch or early lift — might be worth trying. But don’t assume it’s the only way to grow the muscle. More research is needed to understand how this applies across different people and training styles.