The skullcrusher is a classic triceps builder — a lying extension where you lower the weight toward your forehead and press it back up. Here's how to do it with good form, the muscles it works, the mistakes to avoid, and how to program it.
The skullcrusher is a triceps isolation exercise — a lying triceps extension that works all three heads of the triceps brachii, with extra stretch on the long head. You lie on a bench holding an EZ-bar or dumbbells, keep the upper arms fixed, and bend only at the elbows to lower the weight toward your forehead before extending back to lockout. It's one of the most effective ways to add triceps size, and the stretched position at the bottom makes it a strong complement to pressing work.
The skullcrusher is an isolation lift for the triceps. Because the upper arms are angled back over the head, all three heads work — with extra emphasis on the long head that runs up to the shoulder blade.
| Role | Muscles | What they do in the lift |
|---|---|---|
| Primary mover | Triceps brachii | Extends the elbow to press the weight back to lockout |
| Emphasis | Triceps long head | Stretched at the bottom because the upper arms angle back |
| Assisting | Lateral & medial heads | Drive the elbow extension alongside the long head |
| Stabilizers | Forearms, shoulders | Keep the grip steady and the upper arms fixed in place |
Step-by-step form for the lying skullcrusher with an EZ-bar or dumbbells. Start light — form and elbow position matter more than load here.
If you want to train the same pattern with a different emphasis or equipment, these are the common swaps:
The skullcrusher fits on any push, upper-body or arm day, usually after your main pressing. General starting points:
| Goal | Sets × reps | Notes |
|---|---|---|
| Triceps size | 2–4 × 8–12 | Moderate load, controlled lowering, train close to failure on the last set |
| Stretch emphasis | 3 × 10–15 | Lighter, pause at the stretched bottom, keep elbows tucked |
| Frequency | 1–2× / week | Progress by adding a rep or small increment when you hit the top of the range |
Skullcrushers pair well with a joint-friendly tricep pushdown and a compound dip for full triceps coverage. Read up on RPE to gauge how hard each set should feel.
Log every skullcrusher set — weight, reps, and an RPE value — in LiftHero, and it charts your progressive overload and flags personal records so you can watch your arms grow over the weeks. You can add warm-up sets, supersets and rest-timer holds, then drop the movement into a saved routine so it's ready the next time you train. LiftHero records what you log; it doesn't diagnose your form.
It's a triceps isolation exercise. It works all three heads of the triceps brachii, with extra stretch on the long head because the upper arms are angled back. The forearms and shoulders stabilize the weight.
The name comes from lowering the weight toward your forehead or skull. Despite the name, you stop the bar short of your head and control the descent — you never actually let it touch.
Both work. The EZ-bar's angled grip is easier on the wrists and lets you load more; dumbbells train each arm independently and let you rotate the wrists for comfort. Pick whichever feels better on your elbows.
They can bother the elbows if you go too heavy or lock out aggressively. Use a controlled tempo, an EZ-bar or a slight angle, and stop a set if you feel sharp elbow pain.
For triceps size, about 8–12 reps across 2–4 working sets. Keep the elbows from flaring, control the lowering phase, and train close to failure rather than chasing maximal weight.
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This guide is educational and not medical advice. Consult a qualified coach or medical professional before starting or changing a training program.
By Meitar Lazimi, founder of LiftHero · Last updated July 9, 2026.