Triceps pushdowns strengthen the three muscles on the backs of your upper arms responsible for extending, or straightening, your arm. In addition to your triceps, triceps pushdowns also work your shoulders, abdominal muscles and upper back. When performed as part of your regular strength-training routine, pushdowns will help you build stronger, more toned triceps. The triceps pushdown exercise involves resisting against force to straighten your arms and strengthen your triceps. This exercise is typically performed on a cable machine, which features a moveable, adjustable weight platform connected by a cable to handles or a long bar.