RIRLift app icon RIRLift

Exercises

Skull crushers: how to do them, what they work, and what to swap them for

Published October 17, 2026

Skull crushers, also called lying triceps extensions, are a triceps isolation exercise: you lie on a bench and bend only at the elbows to lower a bar or dumbbells toward your head, then straighten your arms. They train all three heads of the triceps, with the long head working hard because your arms point up and slightly back. What makes them work is keeping your upper arms still, so the elbows do all the moving.

Your last ez-bar skullcrusher set

How to do the ez-bar skullcrusher

The skull crusher loads your triceps through a long range with your arms angled back, so the long head gets a deep stretch at the bottom of every rep. A bar, EZ or straight, lets you hold heavier weight than dumbbells allow, and adding a small plate each week is easy to track.

Steps

  1. Sit on the end of a flat bench with an EZ bar or straight bar resting on your thighs, then lie back and press it straight up over your chest.
  2. Grip the bar overhand with your hands a little narrower than your shoulders, and plant your feet flat on the floor.
  3. Let your arms drift back slightly so the bar sits over your eyes rather than your chest; this is your start position.
  4. Bend only at the elbows and lower the bar in about two seconds until it is just above your forehead or just behind the top of your head.
  5. Straighten your elbows to drive the bar back to the start, keeping your upper arms at the same angle the whole time.

Cues

  • Upper arms stay still
  • Elbows point at the ceiling
  • Two seconds down, then press

Common mistakes

  • Turning it into a press: if your elbows swing forward as the bar comes up, the chest takes over; drop the weight until your upper arms stay put.
  • Elbows flaring out to the sides: keep them about shoulder width and pointing up so the triceps, not the shoulders, move the bar.
  • Stopping halfway: lower the bar until your forearms pass horizontal; the bottom of the rep is where the long head is stretched most.
  • Starting with the bar over your chest: tilt your arms back a little so the triceps stay loaded at the top instead of resting.

Swap for: Dumbbell Skullcrusher, Overhead Cable Triceps Extension, Machine Triceps Extension

Muscles the ez-bar skullcrusher works

Skull crushers train the triceps brachii, all three heads, with the long head working hardest because it crosses the shoulder and your arms are angled back. The load is heaviest at the bottom, with your elbows deeply bent and the triceps stretched.

Sets, reps and reps in reserve for the ez-bar skullcrusher

GoalSets × repsRIRRest
Build muscle 3 × 10–15 2 90 s
This matches the session builder; add weight when every set reaches 15 reps at 2 reps in reserve.
Heavier work 3–4 × 6–10 1–2 2 min
Use it as your first triceps exercise when you want to push the load, and keep the two-second lowering on every rep.
At the end of a session 2–3 × 12–20 0–1 90 s
Lighter sets taken close to failure fit after presses, when your triceps are already tired.
Beginners 2–3 × 10–15 2–3 90 s
Start with an empty EZ bar or straight bar or light dumbbells and learn to keep your upper arms still before you add weight.

Ez-bar skullcrusher variations

  • Dumbbell Skullcrusher start position

    Dumbbell Skullcrusher

    Use dumbbells when you have no bar or want to turn your palms to face each other; each arm also has to do its own share.

    Build a session with it
  • Kettlebell Skullcrusher start position

    Kettlebell Skullcrusher

    Pick this when a kettlebell is your heaviest single weight; hold it by the horns with both hands.

    Build a session with it
  • Kettlebell Decline Skullcrusher start position

    Kettlebell Decline Skullcrusher

    Choose the decline version when a flat bench lets your elbows drift; the head-down angle keeps the triceps loaded at the top.

    Build a session with it
  • Landmine Lying Triceps Extension start position

    Landmine Lying Triceps Extension

    Use the landmine when you want a fixed bar path and an easy way to load plates without a spotter.

    Build a session with it
  • JM Press start position

    JM Press

    A heavier mix of a skull crusher and a close-grip press; pick it when you want to move more weight with the triceps doing most of the work.

    Build a session with it

Ez-bar skullcrusher alternatives

Overhead stretch

  • Seated Dumbbell Overhead Triceps Extension start position

    Seated Dumbbell Overhead Triceps Extension

    The closest swap: one dumbbell overhead stretches the long head even further than a skull crusher.

    Build a session with it
  • Overhead Cable Triceps Extension start position

    Overhead Cable Triceps Extension

    Use the rope overhead when you want steady tension and your wrists free to turn; a good pick if the bar feels awkward.

    Build a session with it

Machine or cable

  • Machine Triceps Extension start position

    Machine Triceps Extension

    Same elbow-only movement with no bench to set up, handy when the benches are taken or you want quick weight changes.

    Build a session with it
  • Cable Triceps Pressdown start position

    Cable Triceps Pressdown

    Use pressdowns for higher-rep sets with your arms at your sides; easy to push close to failure.

    Build a session with it

Heavy pressing

  • Close-Grip Bench Press start position

    Close-Grip Bench Press

    Pick this when you want much heavier than any extension, with the chest and shoulders helping.

    Build a session with it
  • Machine Triceps Dip start position

    Machine Triceps Dip

    A loaded dip on a machine for heavy sets without balancing your bodyweight.

    Build a session with it

Bodyweight

  • Close-Grip Push-Up start position

    Close-Grip Push-Up

    Hands under your shoulders and elbows tucked turn a push-up into a triceps exercise you can do anywhere.

    Build a session with it
  • Bench Dip start position

    Bench Dip

    Hands on a bench or chair behind you; straighten your legs to make it harder.

    Build a session with it

EZ bar vs dumbbell skull crushers

A bar, EZ or straight, lets you hold more weight and add it in small steps, so it is the better default when your goal is to load the triceps heavier each week. Dumbbells let your wrists turn to a palms-facing grip and make each arm work on its own, which suits lifters who find the bar awkward or have one arm that lags.

A straight barbell works too; take a grip a little narrower than your shoulders. If it feels awkward, use the EZ bar or dumbbells instead.

Questions

What do skull crushers work?

Skull crushers train the triceps, all three heads. The long head works especially hard because your arms are angled back and it gets stretched at the bottom of each rep.

Which skull crushers are better, EZ bar or dumbbells?

Use the EZ bar when you want to lift the most weight and add it in small jumps. Use dumbbells when you prefer a palms-facing grip or want each arm to work on its own. Both train the same muscle.

Can you do skull crushers with a regular barbell?

Yes. Take an overhand grip a little narrower than your shoulders and follow the same steps. If the straight bar feels awkward, switch to an EZ bar or dumbbells.

What exercise can I substitute for skull crushers?

A seated dumbbell overhead triceps extension or an overhead cable extension is the closest swap, since both stretch the long head. A triceps extension machine copies the movement without a bench. Close-grip bench press and close-grip push-ups work the triceps with heavier or no equipment.

Should skull crushers go to your forehead or behind your head?

Lower the bar to just above your forehead or just behind the top of your head, whichever lets your upper arms stay still. Tilting your arms slightly back and lowering behind your head gives the triceps a longer stretch.

How many sets and reps of skull crushers should I do?

Three sets of 10 to 15 reps, stopping about two reps short of failure, is a good default. Count them toward 10 to 20 hard sets per week.

How do you do skull crushers with a dumbbell standing?

Standing turns it into an overhead triceps extension: hold one dumbbell with both hands behind your head, keep your elbows pointing up, and straighten your arms. Sitting on a bench with back support makes it easier to keep your torso still.