At least that's how it's supposed to work, but, very often, it gets easy to cheat on the move and to cheat yourself out of the tight ab positioning that helps make the skullcrusher really work. But you can't do any of that cheating in this skullcrusher variation from Men's Health fitness director Ebenezer Samuel, C.S.C.S. , which includes a pair of simple tweaks that drive your triceps to work in near-complete isolation.
"We're forcing you to own every aspect of the skullcrusher," says Samuel. "The triceps drives elbow extension, and here, you get to do that with no assistance elsewhere. Then on top of that, you have to own the elbow extension."
It starts with the hollow body position. "Very often, people arch their backs slightly during skullcrushers," says Samuel. You can't do that in the hollow body position, he says, because the position inherently forces you to operate with abs tight, closing your ribcage.
"You're also working at a precise arm angle," says Samuel, "one that makes the straight-arm position of the skullcrusher a position of work." It gives your core a workout too, by virtue of the hollow body position. And because of the pattern of reps you're doing, your abs must constantly adjust and flex in different ways to maintain the hollow body position.
"There's some anti-rotational effect when you do each single-arm rep," says Samuel. "But then that's offset with the two-arm reps."
All you'll need to do the mixed-style hollow body skullcrusher is a pair of dumbbells, so you can do this one anywhere, even at home. Don't have a pair of dumbbells? Check out this pair from Bowflex.
- Lie with your back on the ground, legs straight, two dumbbells held directly over your shoulders. Tighten your abs, pressing your lower back into the ground. Raise your legs an inch off the ground. Raise your shoulder blades off the ground. Keeping your arms straight, shift your upper arms back slightly. "You want your upper arms to not be perpendicular to the ground," says Samuel. "Aim for a 91- or 92-degree angle relative to torso." This is your starting position.
- Bending only at the elbows, lower the weights until they nearly touch your shoulders, keeping the rest of your body tight in the starting position. Press back up, straightening only at the elbows.
- Hold that straight-arm position with your right arm, then do a skullcrusher rep with your left arm, bending only at the elbow. Straighten.
- Repeat that pattern on the other side: Do a rep with both arms, followed by a rep only with your left arm. Do 10 to 12 total pairs of reps.
Use this skullcrusher variation as a workout finisher that slams both triceps and abs. It fits well after a bench press routine, or as the last move in a triceps routine.