Standing Towel Triceps Extension

Trains the Long Head.

How to do it

Hold one end of a towel in both hands overhead, letting the rest hang down behind your back.
Have a partner hold the hanging end behind you and provide resistance, or hold it yourself with the free hand behind the back.
Set the upper arms beside the ears with the elbows bent and pointing up.
Straighten the arms overhead against the resistance until the elbows are locked.
Lower the forearms behind the head under control while the resistance stays on.
Keep the resistance steady rather than yanking; it should feel like a slow weight.

Uneven resistance. A partner who pulls harder on some repetitions than others makes the movement jerky; the pull is steady on both the way up and the way down.
Letting the elbows flare. They point up and stay close together; elbows that drift out let the shoulders join the press.
Arching the back against the pull. The pull comes from behind, and the stomach braces against it rather than the spine bending.
Skipping the lowering. The way down is half of the work, and the resistance stays on while the forearms fold back behind the head.