Skull Crushers Won’t Actually Crush Your Skull. Here’s What Muscles They Work, And Why They’re a Must for Sculpted Arms

Sure, there are tons of ways to train your upper body. But if you truly want to target your triceps—and, BTW, you totally should (more on why later)—start doing skull crushers. Also known as nose breakers, skull crushers work a couple of muscles and involve lying on your back and lowering weight to your forehead. And they sound, well, pretty intimidating. But don’t let the name scare you off: As long as you practice good form, these lying triceps extensions are super safe.

Skull crushers are also extremely effective at building bigger, stronger triceps. Plus, they’re also pretty easy on your elbows (compared to other overhead triceps extension exercises) and boost your bench press prowess, too.

Got your interest? Read on to learn how to do skull crushers correctly, exactly which muscles the move works, and all the plusses it has to offer.

How to do skull crushers with perfect form every time

You can do skull crushers in a bunch of different ways: holding onto dumbbells, a barbell, EZ bars, weight plates, and even resistance bands; you can lie on the floor or a bench. Each variation will work your triceps.

Whichever way you choose, follow these general steps to get the proper form with skull crushers.

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1. Lie on a bench or the floor, holding a dumbbell in each hand.
2. Extend your arms above your head, so they’re directly above your shoulders.
3. Bend your elbows, slowing lowering the dumbbells toward your forehead with control, then press back up.

Muscles worked when doing skull crushers

Skull crushers focus on strengthening your triceps, the muscles located on the back of your upper arm, says Kyle Sanchez, PT, DPT, CSCS, physical therapist and certified strength and conditioning specialist at Bespoke Physical Therapy in New York City. While training the triceps often gets overlooked (many gymgoers spend all their time building bigger biceps), this muscle is massively important for arm function.

“Broadly, the triceps muscle extends the arm at the elbow joint and assists in keeping the humerus stable within the socket,” says Karina Wait, a personal trainer at Life Time Edina in Minnesota. Both things are essential for everyday activities (think: brushing your teeth, combing your hair, reaching for something on a high shelf). Really, any time you bend or straighten your arms, your triceps are at work.

The triceps is capable of all this because it’s a three-headed muscle (this is also where the tri in triceps comes from). “The triceps consist of three separate heads that converge into a single tendon at the elbow,” Sanchez says.

• The long head (stabilizes the shoulder joint, extends your arm at the shoulder, and helps move your arm across the body)
• The medial head (plays a vital role in extending the forearm at the elbow)
• The lateral head (the strongest of all three heads, also helps with elbow extension)

“Skull crushers work all three heads of the triceps,” Wait says. “However, the medial head is the star of the show.” Compared to the other two heads, it’s active in all forms of triceps extension (including the sphinx push-up).

While the triceps is the main muscle targeted in skull crushers, there are other muscles that support the movement. Additional muscles worked during skull crushers, according to Wait:

• Deltoids: stabilize the shoulder joint during the skull crusher
• Upper back and lats: stabilize the entire body on the bench
• Forearm muscles: stabilize the weight during the movement

5 benefits of skull crushers that’ll convince you to add them to your workouts

If they’re not already, skull crushers should be a staple in your weekly workouts. Here are just a few reasons why.

1. They isolate and build the triceps

Whenever you bend or extend your arm, your triceps are be involved, making strong, healthy triceps a top priority.

To train your triceps properly, you have to isolate the muscle. And skull crushers do just that: “Because they target all three heads of the triceps, it’s a great bang for your buck exercise,” Wait says.

Plus, the position of the movement (lying on your back) takes momentum out the equation. With standing exercises, we can use momentum to lift the load (especially after a few reps, when it’s starting to feel heavy). The problem with that is you don’t get the full benefit of the move. Skull crushers don’t give us any room to cheat ourselves.

2. They support shoulder health

The long head of the triceps attaches to the scapula, your shoulder blade. “More specifically, the long head contributes to extension and adduction at the shoulder joint,” Wait says. It also plays a pivotal part assisting with shoulder joint stability, she says.

So skull crushers,