This exercise is used to isolate the lat muscles but will also slightly work your chest muscles.
Begin by attaching a straight bar attachment to a high pulley on the cable machine. Next, stand in front of the cable machine about 2 feet away from it and face the machine. Now, reach up and grab the bar with palms down grip and your hands should be slightly wider than your shoulders. Lean slightly forward at your waist and keep a slight bend in your elbows; move your arms so that they are extended directly in front of you. Now, tighten your lats and pull the bar down until your hands are by your sides; keep your arms extended throughout the entire movement. Continue to keep your arms straight as you slowly return the bar back to the starting position. Repeat this movement until you have completed your set.
If your arms are not fully extended throughout the movement, you should take a step back from the machine.
This movement can also be done with a barbell while lying on a flat bench.