Lie supine on a bench with a barbell or EZ curl bar pressed up above you. Bend the elbows and allow them to move back slightly to bring the bar past the top of the head. Keeping the upper arms slightly behind vertical to maintain tension through the entire range of motion, extend the elbows into full lockout, avoiding flaring them out to the sides, then lower again under control.
 
Purpose
The skull crusher trains the triceps and can be loaded heavily.
 
Programming
Generally sets of 6-15 reps are appropriate.
 
Variations
Skull crushers can be done with a barbell, EZ curl bar, dumbbells, kettlebells, or low cable. They can also be done on an incline bench, or with a supinated grip.