Muscles worked
Your triceps straighten the elbow and do almost all of the work. With your arms overhead, the long head, the part of the triceps attached to your shoulder blade, is put on a stretch at the bottom. Doing it seated on a bench with a backrest spares your trunk the job of keeping you steady, and often lets you handle a little more weight.
Common mistakes
- An insecure grip on the dumbbell. Holding only the handle lets the dumbbell twist and slip. Turn it upright, press your palms flat against the inside of the top end and let the handle hang down between your hands.
- Pushing your chin forward. To make room for the dumbbell, many people poke their head forward and strain the neck. Keep your head straight, eyes forward, and let your arms move around it.
- Using momentum out of the bottom. It is tempting to let the dumbbell drop behind your head and rebound. Lower slowly, change direction without momentum and press up with your triceps.
Variations and alternatives
- The overhead cable extension gives more even resistance and smaller weight steps in the gym.
- The single arm overhead extension works one arm at a time, useful if your arms differ in strength.
- The skull crusher is done lying down, an option if your shoulders dislike having your arms straight overhead.
- The backpack overhead extension does the same movement at home when you have no dumbbells.
Sets and reps
For muscle, 8 to 12 reps over 2 to 4 sets works well, with 12 to 20 for endurance. Going really heavy is rarely worth it, as a heavy dumbbell is hard to get overhead and to control behind your neck. Which ranges suit which goal is set out in the guide to sets and reps.
Gym dumbbells often go up by 2 kg or more, a big jump for the triceps alone. Add one rep at a time with the same dumbbell until you reach the top of your range on every set, and only then move up. That is progressive overload. If your elbow or shoulder hurts, rather than just feeling heavy, stop and have a doctor or physiotherapist look at it.