[@Drifting Pollen]
I left that part open ended because he really does have flat out total control of his body, and can pretty much do anything that is physically humanly possible, least of all in theory only. To list all of the little odds and ends would take a long time, and they are already pretty obvious. Things like high flexibility, muscular control, perfect balance, and other obvious incidental stuff that accompanies someone stated to be "the supreme master of his own body..." that "can control its functions at will." 

Yes, that includes deciding when he can poop down to the last second.