Stand facing a cable stack with a v-bar attached to a high pulley. Take an overhand grip on the V-bar bend your knees slightly and lean forward at your waist 10 degrees or so. Begin with your elbows bent just less than 90 degrees and in tight at your sides. Keeping your elbows in a fixed position (not flaring out or moving forward or backward) press the bar down by straightening your arms as you exhale. When your elbows reach full extension squeeze the contraction for a count. Slowly return to the starting position (your elbows just less than 90 degrees) and repeat for reps. For added intensity try drop sets then lighten the weight and go to failure with that and drop it again one or two more times. Pressdowns are ideal for drop sets because lightening the load is as easy as pulling out the pin.