Stretched-position curls for a fuller bicep.
Keep your upper arms back and still. The stretch at the bottom is the whole point.
Leaning back on the incline lets your arms hang behind your body, putting the biceps under stretch at the very start of every rep, a position standing curls never visit. Curling from that lengthened state loads the muscle where it is weakest and most responsive, which is why this variation has a reputation for building fuller arms. It earns its place as the stretch curl in a dumbbell rotation, the counterpart to squeeze-focused movements like preacher or concentration curls.
Around 45 degrees is the sweet spot for most people. Lower angles increase the stretch but get harsh on the shoulder, more upright angles drift back toward a standard curl. Start at 45 and adjust to what your shoulders tolerate.
Because the stretch position removes all your usual help. There is no torso lean, no momentum, and the biceps start from their weakest length. Lighter dumbbells here are not a downgrade, they are proof the biceps are actually doing the work.
A mild stretch sensation there is normal since the biceps cross the shoulder. Sharp discomfort means the angle is too low or you are letting the shoulders roll forward. Raise the bench a notch and pin your upper arms back and still.
