This exercise provided courtesy of Mike Clausen, founder and co-owner of DIAKADI Body training gym, voted best personal training gym in San Francisco by CitySearch in 2006.
Skull crushers are a deceptively simple triceps exercise. You work the triceps by moving the lower arm—but you also have to stabilize your upper arm, making the exercise more of a challenge. If your upper arm swings around, you may find out how this exercise got its name—so be careful.
Lie on your back on a flat bench with your head near one end and a dumbbell in each hand. Extend your arms toward the ceiling, but at a 45-degree angle behind the vertical, such that even in the starting position you can feel tension in your triceps. Your palms should be facing each other. Cross your feet at the ankle and lift your legs up off the bench so that your upper legs are perpendicular to the bench, your knees are bent at a 90-degree angle, and your lower legs are parallel to the floor (see Photo 1).
- From the starting position, keep your upper arms immobile as you bend your elbows and lower your forearms toward your head. Do not hit yourself in the head with the weights—instead, keep your hands at shoulder width throughout. Keep your shoulders back and your elbows high as you do these (see Photo 2 and 3).
- At the bottom of the movement, reverse direction and bring your hands back to the starting position, again without changing the position of your upper arm, to complete one repetition; your tightest flexion will be at the top of the movement, so be careful to control the upward movement as much as the down. If you begin to struggle before the end of the set, bring your upper arms closer to vertical to lessen the intensity (see Photos 4 and 5).