Skull Crusher: What It Does, How to Do It, and Who It's Worth It For

How the skull crusher loads the long head of your triceps, step-by-step technique, sets and reps that work, and what to do when your elbow hurts.

The skull crusher is a triceps isolation exercise done lying on a bench, lowering a bar or dumbbells toward your forehead or behind your head. The name is worse than the movement — in practice it's one of the few exercises that properly loads the long head of the triceps, the part close-grip pressing mostly skips. Here's what it actually does, how to do it without picking a fight with your elbows, and when it's worth a slot in your program.

What the skull crusher does that presses don't

The triceps has three heads: long, lateral and medial. The lateral and medial heads originate on the upper arm and work in every pushing movement — close-grip bench, dips, push-ups, overhead press. The long head originates on the shoulder blade and is the only one that crosses the shoulder joint, so it reaches full stretch only when the upper arm is raised overhead or pushed behind the line of the torso.

That's where the skull crusher earns its place. If you lower the bar behind your head rather than strictly to your forehead, the upper arm travels back and the long head works under load in a stretched position. The practical math is simple: if you train some form of pressing 3 times a week, the lateral and medial heads already get plenty. What's missing is a movement with the arms overhead — a skull crusher or an overhead triceps extension.

Technique, step by step

Lie on a flat bench, feet planted, shoulder blades pulled together. Take an EZ bar with hands 20–30 cm apart. A straight bar loads the wrists more, so EZ bar or dumbbells suit most people better.
Extend your arms, but not straight vertical. Tilt the bar 15–20 degrees toward your head so the triceps is already under tension at the start. With fully vertical arms your skeleton holds the weight, not the muscle.
Keep your elbows in place and pointing forward. Letting them flare out sideways is the clearest sign the weight is too heavy.
Lower under control over 2–3 seconds, past your ears, until the bar is behind your head roughly 5–10 cm above the bench.
Pause half a second at the bottom. No bouncing, no swing.
Press back up in about 1 second, stopping just short of full lockout. No resting at the top.
Inhale before lowering, exhale on the way up. A set of 12 reps done this way takes 45–55 seconds.

Forehead, chin or behind the head?

All three versions work the triceps, but they're not equal. Lowering strictly to the forehead gives a shorter range and more pressure on the point of the elbow. Lowering behind the head gives the biggest long-head stretch and, for most people, less elbow discomfort because the load is spread over a longer path. Start with the behind-the-head version and only change it if your shoulder objects.

Variations and when to pick each

EZ bar — the standard. Friendlier wrist angle, easy to add weight in 1 to 2.5 kg jumps.
Dumbbells, neutral grip — each arm works alone, so a weaker side shows up immediately. Good if a bar bothers your wrists.
Low-pulley cable, lying on a bench — tension stays even through the whole range, including the top. The easiest version on the elbows.
Seated overhead dumbbell extension — not a skull crusher, but it fills the same role when no bench is free.

The common mistakes

Too much weight, so the elbows drift forward and the lift turns into a close-grip press.
Locking out and resting at the top — the triceps is off the hook in that position.
Cutting the range short, stopping halfway down to the forehead.
Heavy sets of 4–6 reps. The triceps tendon in this position doesn't handle very heavy low-rep work well.
Putting the exercise first in the session, leaving nothing for the presses that carry more weight.

Sets, reps and load

For muscle growth: 3–4 sets of 8–15 reps, 60–90 seconds rest, twice a week. A total of 6–10 direct triceps sets per week is plenty if you're already pressing. Finish each set with 1–2 reps left in reserve; take only the last set close to failure.

Progression: once you hit the top of the range (say 4×12) two sessions in a row, add 1–2.5 kg and go back to the bottom of the rep range. An empty EZ bar weighs 7–10 kg and is a perfectly reasonable starting point if this is new to you. Placement: at the end of an upper-body session, in the last 10–15 minutes.

If you have to throw your elbows around to finish a rep in the third set, the weight is 5 kg too heavy, not 2.5.

Elbows: what's normal and what isn't

A stretching sensation in the triceps and mild tightness around the elbow the next day are common, especially in the first 2–3 weeks. What isn't normal is a sharp, pinpoint jab at the tip of the elbow on every single rep.

If discomfort shows up: drop the weight by 20–30%, switch to cables or dumbbells, shorten the range to avoid the painful spot, and stay there for 2 weeks. If it improves over that time, build back gradually. If it doesn't, stop pushing through it.

When to see a doctor

Pain lasting more than 2–3 weeks despite reduced load.
Visible swelling, redness or warmth around the elbow.
Tingling or numbness in the little and ring fingers, or grip strength dropping off.
Pain that wakes you at night or interferes with everyday movements.
A sudden pop during a set with immediate loss of strength — same day, don't wait.

This is general training information, not a substitute for an examination.

Who it's worth it for — and who it isn't

It's worth it if you've been training at least 6 months, do two or three upper-body sessions a week, and want thicker arms or a stronger lockout on the bench press. It's also worth it if your shoulder doesn't get along with dips — the skull crusher gives a similar effect with far less shoulder load.

It isn't worth it in your first 8–12 weeks in the gym; close-grip bench and push-ups will give you more for the same time. And it isn't worth it if you train twice a week with six full-body exercises — there's simply no room for isolation work.

The short version

The skull crusher is one of the few movements that loads the long head of the triceps in a stretched position.
Lower behind your head, keep the elbows still, 2–3 seconds down, no lockout at the top.
3–4 sets of 8–15 reps, 60–90 seconds rest, twice a week, at the end of the session.
Use an EZ bar or cables instead of a straight bar if your wrists or elbows complain.
Elbow pain past 2–3 weeks, swelling, or tingling fingers — get it checked.