Pushdowns are great for isolating your triceps. You can utilize the Reverse Grip Pushdown as a starting exercise to warm up your elbows or to finish off your triceps with a great pump. Here we work the triceps through a full range of motion. The reverse grip version of the pushdown keeps your form more strict.
Attach a short bar to an overhead pulley cable, stand in front of the bar and grab it with an underhand grip, hands a little less than a foot apart.
Make sure that your elbows are in close to your body and stay fixed during this movement. Try and keep your whole body as still as possible. Don’t lean on the weight with your body, it takes the workload off of your triceps. Now, press the bar down locking out your arms and feeling a peak contraction in the triceps. Release and let the bar come up as far as possible without moving your elbows.
To shock your muscles, you can vary your grip change the kind of bar you use, how close you stand to the cable machine, or how wide your place your hands; or you can do a three-quarter movement, going from all the way up to three-quarters of the way down in order to work the lower triceps more directly.
In the video below the great Rob Riches demonstrates how to perform both the overhand and reverse grip variation of the tricep pushdown.