The triceps extension machine seats you with the upper arms fixed and pushes the weight through elbow extension alone, so nothing leaks into the shoulders or the trunk. Its real advantage is that the fixed path lets you go to failure and beyond without a bar wandering anywhere near your face, which is more than a skull crusher can say.
How to do it
- Set the seat so your elbows sit on the pad without shrugging.
- Full extension every rep, then control the return.
Common mistakes
- Half reps at a heavier setting instead of full reps at a lighter one.
What it trains
- Triceps
- extend the elbow against the pad — the only muscle doing anything here
- Forearms
- hold the handles and keep the wrists neutral
Variations and alternatives
Common questions
Is a machine extension as good as a skull crusher?
For building the triceps, close enough that it is not worth agonising over. The machine wins on safety and on how hard you can push a final set; the skull crusher wins on loading the long head through a stretch if the machine keeps your arms at your sides. Which one a given machine matches depends on its arm position.
How do I know the seat is set right?
Your elbows should line up with the machine's pivot, and your upper arms should rest flat with the shoulders down. If your elbows sit in front of or behind the pivot, the machine fights you through part of the range and the load feels lumpy.
What rep range should I use?
Ten to fifteen. The triceps respond well to higher reps on isolation work, and the machine is stable enough that the last few grinding reps are still clean ones rather than a form collapse.
In StackUp. Logged as weight and reps per set, and your heaviest working set decides whether the weight goes up next time. Get the app.
Arms
