We all know it must have sucked to be nailed to a cross. Now to add to injury, imagine you really had to pee but still had some sense of vanity in that hopeless situation. That's what this exercise is like, but somehow your legs have managed to escape the nails and are able to swing from side to side while your upper body stays put and arms stretched to each side. It's hard! Once you've mastered it, try doing it with straight legs!
No one, not even superheroes will help you.
Other people call this exercise the pendulum. What do they know.