STARTING POSITION:
Select the appropriate resistance in the weight stack. Place the pulley in the lowest position and a bench in front of it. Lie back on the bench placing the feet away from the pulley. There should be a cable bar that is attached to the pulley. Grab it using a prone grip and place it above your head with your arms straight. The arms should be perpendicular to the floor. Contract your pelvic floor and core.
MOVEMENT:
Start lowering the bar only moving the forearms until the bar almost touches your forehead while you inhale. Return to the starting position in a strong movement by extending your arms while you exhale.
TIPS: While your are doing the exercise, move only the elbows joint, make sure you don't move any other part of your body.