Here's one to try at home - but make sure you have some soft carpet to land on. It's the very difficult movement of exercise ball push-ups with feet elevated.
I can do one or two before I buckle. Core strength, balance, patience and upper chest and arm power are necessary to keep your body stable.
I attempt to crank out a few fast reps, but fast won't work. It's about slow, methodical movement while maintaining perfect balance. Every muscle in your body goes taut with the effort.
So, tonight I might have a Heineken and give it another try. Take a shot at this and let me know how you do.