For women who work out regularly, both preacher curls and inclined curls build arm muscle just about the same way — no matter where you look along the upper arm.

For women who work out regularly, doing preacher curls that stretch the biceps a lot might help build more muscle in the lower part of the upper arm—about an 8.8% increase—compared to other curl types.

For women who work out regularly, doing preacher curls or incline bicep curls doesn't seem to change where their biceps grow — both exercises lead to similar growth patterns after 9 weeks.

If young women do bicep curls on an incline bench, they’ll likely grow the upper part of their biceps more, but if they use a preacher curl bench, they’ll grow the lower part more — the way you curl matters for where your muscle grows.

Doing a specific type of bicep curl on an incline with changing resistance doesn't seem to make certain parts of the upper arm muscles grow more in women who work out regularly — even after doing it consistently for 9 weeks.

For beginners, lifting weights with one arm or both arms at the same time results in similar biceps growth, indicating that the total amount of weight lifted and number of repetitions matter more than whether one or two arms are used.