Skull crushers: Want bigger

Want bigger, stronger triceps? Find out how to do skull crushers safely, the muscles worked, pro tips, common mistakes, and the best exercise variations. Learn how to do skull crushers with proper form and try variations for different fitness levels. Follow our step-by-step instructions and tips. Skull crushers are a tricep-focused upper body push exercise that works all three heads of the tricep, but the long head is the primary muscle worked. Skull crushers can be done using dumbbells, barbells, and resistance bands. The dumbbell skull crusher exercise (or the Triceps Extension) is a tried-and-true triceps exercise intended to develop that horseshoe-shaped muscle on the back of the arm.