STARTING POSITION:
Grab the pull up bar with your hands slightly wider than shoulder width apart and with your palms facing forward. Your elbows should be fully extended and your shoulders relaxed.
MOVEMENT:
Retract your shoulder blades rising your chest up. Contracting your back muscles, pull your upper body up until your chin is above the bar while you exhale. Return to the starting position in a smooth movement while you inhale. Raise your upper body up again, but now the bar should touch the back of your neck.
TIPS: The exercise key is quality over quantity. The trick is to perform the exercise using proper form. Make sure your shoulders are far from the ears when you perform the ascent to the bar.