The dumbbell preacher curl emphasizes bicep isolation, using a preacher bench to maintain strict form. This exercise targets the lower biceps, promoting muscle growth and definition.

1. Sit on a preacher bench with a dumbbell in one hand.
2. Rest your arm on the pad and curl the dumbbell towards your shoulder.
3. Squeeze your bicep at the top of the movement.
4. Slowly lower the dumbbell back to the starting position.