What muscles do skull crushers work?

The triceps, all three heads, with the long head working in a stretched position because the arms point slightly back over your head.

Are skull crushers bad for your elbows?

Not for most people with a sensible weight and controlled reps. If they hurt, lower the bar behind your head instead of to your forehead, try an EZ bar or dumbbells, or switch to a cable version.

Should I lower the bar to my forehead or behind my head?

Either works. Behind the head keeps a little more tension on the triceps at the top and often feels better on the elbows; to the forehead is the classic version.

Skull crushers or overhead extensions?

Both stretch the long head of the triceps. Skull crushers are done lying down and are easy to load with an EZ bar; overhead extensions work it in an even longer position. Many programmes use one of each, or alternate them.

Skull Crusher: Muscles Worked and How to Do It

Skull crusher: muscles worked and how to do it

The skull crusher trains your triceps, the muscle on the back of your upper arm. It is an isolation exercise: you lie on a bench and only your elbows bend and straighten, so the triceps does all the lifting. Because your arms point up and slightly back, the long head of the triceps works in a stretched position.

You lower an EZ bar or a pair of dumbbells towards your forehead (or just behind your head) by bending your elbows, then press it back up. The name is a warning as much as a description: control the weight, and pick one you can stop at any point.

At a glance

Main muscles: Triceps
Movement: Straighten the elbow
Equipment: Barbell, Dumbbells, Flat bench
Type: Isolation (one joint)

Front

Back

How to do a skull crusher

Lie on a flat bench with your feet on the floor and hold an EZ bar above your chest with straight arms, hands about shoulder-width apart.
Tilt your arms back slightly, so the bar sits above your eyes rather than your chest.
Keeping your upper arms still, bend your elbows and lower the bar slowly towards your forehead or just behind the top of your head.
Stop when your forearms are about level with the bench or you feel a good stretch in the triceps.
Straighten your elbows to press the bar back to the start, without letting your elbows flare out.

Cues that help

"Elbows point at the ceiling": your upper arms stay put and only the forearms move.
"Elbows in": keep them about shoulder-width, not flaring out to the sides.
"Slow down, fast up": take two to three seconds to lower the bar.
"Behind the head" if your elbows complain: lowering a little further back often feels better than aiming at the forehead.

Safety first

The bar travels over your face. Use a weight you can stop and hold at any point of the rep, and finish each set a rep or two short of failure.
Ask a training partner to hand you the bar and take it back on heavy sets, or start with the bar on the floor and pull it over.
If your elbows ache, switch to dumbbells or a cable version, which let your wrists and elbows find their own path.

Common mistakes

Moving the upper arms. When the elbows swing forward and back, it turns into a pullover and a press, and the triceps does less.
Elbows flaring out, which puts strain on the elbows and shortens the range.
Dropping the bar too fast. The lowering is where control, and safety, come from.
Going too heavy. Skull crushers are an accessory; moderate weights with clean reps work better than grinding heavy ones.

Sets, reps and weight

For muscle: 3 to 4 sets of 8 to 15 reps.
Rest about 1.5 to 2 minutes between sets.
An EZ bar is usually kinder to the wrists than a straight bar.
Progress with reps first, then with small jumps in weight.

Variations and alternatives

Dumbbell skull crusher: a dumbbell in each hand, palms facing each other.
Incline skull crusher: on an incline bench, which keeps the triceps under tension at the top.
Cable skull crusher: lying with a rope or bar on a low pulley.
Overhead tricep extension: the same stretch on the long head, standing or seated.
Tricep pushdown: a simpler cable option for higher reps.

Tracking your skull crushers

PushBeyond logs the weight and reps of each set and charts the history of the exercise. Its muscle map counts the skull crusher for your triceps.