How to Do It
- Lie on a flat bench holding a barbell, EZ-bar, or dumbbells with arms extended straight above your shoulders.
- Keep your upper arms fixed and vertical, only bending at the elbows for the entire movement.
- Lower the weight by bending your elbows until it reaches just above or behind your forehead.
- Keep your elbows pointed at the ceiling throughout the descent rather than letting them flare outward.
- Extend your elbows to press the weight back to the starting position, stopping just short of a hard lockout to keep tension on the triceps.
Common Mistakes
- Letting the elbows drift forward or backward instead of staying fixed in one vertical position throughout the set.
- Lowering the weight too far past the head, which puts unnecessary strain on the elbow joint.
- Using shoulder movement to help lower and raise the weight instead of isolating the motion at the elbow.
- Going too heavy, which is the main cause of the elbow flare that turns this into an unsafe, joint-stressing lift.
The skull crusher, more formally a lying triceps extension, stretches the long head of the triceps under load more directly than pushdowns or close-grip pressing, since the upper arm stays overhead throughout the movement.[1][2]
An EZ-bar is the most forearm-friendly option for most lifters, since the angled grip reduces wrist strain compared to a straight barbell. Dumbbells work well too and allow a slightly more natural wrist path.
Combine it with tricep pushdowns in a superset on arm day to train the long head and lateral/medial heads in the same session.
Muscles Worked by the Skull Crusher
The skull crusher isolates the triceps almost entirely, with the long head taking on more of the load than in most other triceps exercises because it stays under stretch throughout the movement.[1][2]
- Primary: triceps brachii, particularly the long head
- Secondary: forearm flexors, which stabilize the grip on the bar or dumbbells
- Stabilizers: anterior deltoids and shoulder stabilizers, which keep the upper arm fixed and vertical instead of drifting
Because the upper arm stays overhead throughout, the long head of the triceps stretches under load in a way that pushdowns, which keep the arm at your side, do not replicate.[1][2]
Skull Crusher vs Tricep Extension
Both isolate the triceps with the arm overhead, but the joint that moves and the equipment used set them apart.[1][2]
The skull crusher, done lying on a bench, bends only at the elbow with the upper arm fixed vertically, letting you use a straight bar, EZ-bar, or dumbbells. The seated or standing overhead tricep extension moves through a similar elbow path but from a vertical torso position, usually with a single dumbbell or cable, and tends to allow a slightly greater stretch at the bottom.
| Skull Crusher | Overhead Tricep Extension | |
|---|---|---|
| Body position | Lying on a bench | Seated or standing |
| Equipment | Barbell, EZ-bar, dumbbells | Dumbbell or cable, usually single |
| Stretch at bottom | Moderate | Slightly greater |
| Elbow stress | Lower, supported by the bench | Higher without back support |
Rotate between the two if one starts to irritate your elbows, since the joint stress profile differs slightly even though the target muscle is the same.
Skull Crusher Alternatives
- Tricep pushdown: trades the overhead stretch for constant cable tension, easier on the elbows for lifters who find skull crushers uncomfortable.
- Overhead tricep extension: a seated or standing variation with a similar stretch, using a single dumbbell or cable instead of a bar.
- Close-grip bench press: shifts from isolation to a compound press, adding triceps volume alongside chest and shoulder work.
- Dumbbell shoulder press: not a direct substitute, but a useful compound pairing on the same push day for total triceps volume.
If elbow discomfort persists across all variations, dropping the load and tightening the elbow path usually resolves it before an equipment swap does.[1][2]
References
- Anaerobic and Muscle Endurance Development: Lifting Guidelines. National Strength and Conditioning Association (2017)Back to claim
- American College of Sports Medicine Position Stand. Resistance Training Prescription for Muscle Function, Hypertrophy, and Physical Performance in Healthy Adults: An Overview of Reviews. Medicine & Science in Sports & Exercise (2026)Back to claim
- Updating ACSM's Recommendations for Exercise Preparticipation Health Screening. Medicine & Science in Sports & Exercise (2015)
See our exercise methodology for how this evidence is applied and its limits.
Frequently Asked Questions
- Should a skull crusher go behind the head?
- No, a skull crusher should lower the weight toward or just behind your forehead, not all the way behind your head. Keep your upper arms fixed and vertical throughout, bending only at the elbows, and stop the descent once the weight reaches just above or slightly behind your forehead to avoid unnecessary strain on the elbow joint.
- How do you know if you're doing skull crushers correctly?
- You are doing skull crushers correctly if your upper arms stay fixed and vertical throughout the set, your elbows point at the ceiling instead of flaring outward, and the weight lowers to just above your forehead before pressing back up. If your shoulders move to help lift the weight, the load is too heavy for strict form.
- What are skull crushers good for?
- Skull crushers are good for building triceps size and strength, particularly the long head, since keeping the upper arm overhead throughout the movement stretches that portion of the muscle under load more directly than pushdowns or close-grip pressing. They are a reliable isolation accessory for arm day or after a pressing session.
- Are skull crushers actually effective?
- Yes, skull crushers are an effective triceps isolation exercise, particularly for the long head, which stays under stretch throughout the movement in a way many other triceps exercises do not. Using an EZ-bar or dumbbells rather than a straight barbell reduces wrist strain while keeping the same training benefit.
- How to correctly do skull crushers?
- To do skull crushers correctly, lie on a flat bench with your arms extended straight above your shoulders, then bend only at the elbows to lower the weight toward your forehead while keeping your upper arms fixed and vertical. Press back up without letting your elbows flare outward, and stop just short of a hard lockout to keep tension on the triceps.
- How to EZ bar skullcrusher?
- To do an EZ-bar skull crusher, grip the angled bends of the bar with a shoulder-width, semi-supinated grip, which is easier on the wrists than a straight bar. Follow the same form as the standard version: upper arms fixed and vertical, elbows lowering the bar toward your forehead, then pressing back to a near-lockout.