STARTING POSITION:
Select the appropriate weight of the dumbbells. Grab the dumbbell with a neutral grip and lie on a mat on the floor. Fully extend the arm so that it's perpendicular to the floor. Contract your pelvic floor and core.
MOVEMENT:
Start lowering the dumbbell only moving the forearm until the dumbbell almost touches your forehead while you inhale. Return to the starting position in a strong movement by extending your arm while you exhale. Repeat the movement for the specified amount of repetitions and then switch sides and repeat with the other arm.
TIPS: While your are doing the exercise, move only the elbows joint, make sure you don't move any other part of your body.