The dumbbell hammerpreachercurl is a good exercise for isolating the biceps, working the forearms, and making the muscles work independently. Adjust the height of the seat on the preacher bench so that when you sit on it, the back of your upper arms sitcomfortably flat on the padding.

Grab a set of dumbbells and sit on the preacher bench.

Your arms should be resting on the padding and be around shoulder width apart.

You willbe using a neutral grip (palms facing each other).

Allow the weight to drop and arms to fully extend. This is the starting position for the exercise.

Slowly curl the dumbbells up as far as possible, squeezing the biceps at the top of the movement.

Lower the weight back until your arms are fully extended, and then repeat for desired reps.