STARTING POSITION:
Select the appropriate weight of the dumbbell. Lie back on a fitball moving your right arm to hold the dumbbell with a neutral grip just above you with your elbow slightly bent. Your trunk should be parallel to the floor. Retract your shoulder blades rising your chest up.
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 arms while you exhale. Repeat the movement for the specified amount of repetitions and then 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. Make sure your shoulder blades are always retracted.