Muscle Group: 

Attach a straight bar to the pulley on the floor.

Stand with your feet shoulder width apart, your abs drawn in and your back straight.

Grasp the bar with an overhand grasp (your palms facing downwards) and pull it up towards your waist, this is the starting position.

Raise the bar up to in line with your shoulders.

Pause at the top and rotate your shoulder blades together.

Lower the bar in a controlled motion to the starting position.