Lie flat on the bench, take the barbell directly above your chest with arms extended. Keeping the upper arms straight up, hinge only at the elbows, bringing the weight down towards your head (hence the name). Keeping control the whole time, extend slowly up, and squeeze at the top. Make sure your elbows stay in the same position throughout the exercise. You can use a straight bar, or an EZ bar to work a different angle of the tricep.