Doing “skull crushers” might not sound particularly good for you, but if you’re looking to add size and strength to your arms, this triceps-intensive exercise is a great option.
“The skull crusher is an effective way to work all three heads of your triceps,” says Trevor Thieme, C.S.C.S., Openfit’s senior manager of fitness and nutrition content. “Especially if you use dumbbells, which work each arm independently, increasing the instability of the exercise and, thus, muscle recruitment in your arms, shoulders, and core.”
Plus, change up your grip and/or the angle of your bench, and you can emphasize different heads with the skull crusher exercise to build balanced, strong triceps that turn heads.
How to Do the Dumbbell Skull Crusher with Perfect Form
- Lie down on a bench or the floor holding a pair of dumbbells directly above your chest with your palms facing each other. Your feet should be flat on the floor.
- Without moving your upper arms, bend your elbows and slowly lower the weights toward the sides of your head. Avoid flaring your elbows.
- Reverse the move to return to the starting position.
How to Make the Skull Crusher Easier
Besides using lighter weights, you can do EZ bar or barbell skull crushers. The bar transfers the work of stabilizing the weight across both arms, allowing you to lift slightly more.
How to Make the Skull Crusher Harder
Increasing the amount of weight is the simplest way to intensify skull crushers, but slowing down the pace of movement will also make the move more challenging.
Bonus Tips for Doing the Skull Crusher
Your upper arms should remain vertical to the floor for the duration of each set. The only parts of your body that should move are your forearms. Also, speed is not your friend with this exercise. It’s not a power-building move. Lower and lift the weights slowly and under control. Not only will that increase your triceps’ time under tension — a key muscle growth stimulus — but it will also reduce your risk of injury.
Variations on the Skull Crusher
Effective variations on the move include changing your grip (e.g., from neutral to overhand), and changing the angle of the bench (e.g., from flat to incline or decline). Switching up how you perform the exercise can change which head of the triceps is emphasized, enhancing overall muscle development and strength gains.
Benefits of the Skull Crusher
In addition to being a highly effective triceps builder, the skull crusher can be performed with a variety of equipment. Whether you do a dumbbell skull crusher, barbell skull crusher, or use an EZ bar, go as heavy as you safely can, and you’ll see results.
What Muscles Does the Skull Crusher Work?
Two thirds of your upper-arm musculature is occupied by your triceps, and the skull crusher is one of the most effective ways to build them. All three heads of the triceps (lateral, medial, and long) fuse together and attach to the top of your forearm, with the lateral and medial heads originating at the humerus (upper arm bone) near the shoulder, and the long head originating at the scapula (shoulder blade).
The lateral and long heads are the most visible ones, forming the classic “horseshoe” shape associated with well-developed triceps (long on the inside, lateral on the outside). The medial head lies under the other two, and while it doesn’t contribute much to the shape of the muscle, it adds substantially to its overall mass.