Here is all kind of core and edurance training in pushup position.
IF you can do this for four minutes you the man. I would guess most people would not be able to do a minute.

http://www.youtube.com/watch?v=39YH5DU7oZE

This dude crazy lol.. definately great stuff here... Ima do most of these every night

I tried all of them. 4 minutes, yeah right. Forget about core strength, you nee strong shoulders and whole lot of cardio to do this. Very good conditioning. Much more difficult that it looked at first.

I'ma start trying that to see how well I do.