STARTING POSITION:
Select the appropriate weight of the dumbbell. Sit on a bench. Grab the dumbbell from the end with your right hand and place your forearm on your leg. Use a neutral grip.
MOVEMENT:
Slowly pronate your forearm, let the dumbbell go down as much as you can. Return to the starting position. Repeat the movement for the specified amount of repetitions, then switch sides and repeat the exercise.
TIPS: The exercise key is quality over quantity. The trick is to perform the exercise using proper form.