Set-up: Find the pull-down apparatus and a wide grip bar. Attach the bar and adjust the knee rests. Grip the bar near the ends, establish a tight midsection and a neutral spine.
Lift: Pull the bar down until it lightly grazes your chest. Return the weight back to the starting position under control. As you pull, cue yourself to push your elbows down, which will increase involvement from the lats.
Emphasis: Do not swing - your back should move very little from the starting position.
Benefits: The primary target of the pulldown is the latissimus dorsi. While the middle back is also involved to a lesser degree in the exercise, the vertical nature of the pull tends to take the muscles of the mid back out of the movement.