This is a great exercise for the back.  Muscles Involved:  Primary back with a secondary emphasis on the shoulders and biceps.

Body Alignment:
o Sit on the seat of a pulldown machine.
o  Position your body so that your thighs fit under the leg pads.
o  Your feet should be flat on the floor.
o  Brace the transverse abdominals.

Movement:
o  Reach up and take a shoulder-width grip of the bar with your palms facing you
o  Stretch upward in this position and then pull the bar down toward your upper chest while keeping your elbows in close to your body.
o  Slowly let the weight back up
o  Repeat

Training Tip:

Keep your head and neck in a straight line and do not arch your back to help with the weight of the bar.