What is the most physically demanding sport?

Here is the answer according to ESPN.

You can get as many answers as the number of people you ask.The 400 meter hurdles was once called the man killer. The marathon and the triathalon including the decathalon have to be considered.Certainly professional boxers and olympic freestyle wrestlers would ply their cases for their respective sports, professional bodybuilders have to be on 24 7 as well.Mma fighters are no slouches in the training and demanding area.Anyone who can survive a kickoff in an amatuer or pro football game has a clue as to how demanding football is.As a former world champion any sport where one achieves a level of extrordinary excellence knows first had the sacrifice,discipline, and consistence necessary to do so, even if its chess. You train the mind not the body. The body is just along for the ride.Confused?Getting up tomorrow is demanding, the extent and level is arbitrary. Effort is the only truth because only you know how hard you try. Train on brothers and sisters, train on.

Hockey is without a doubt the most physical.  Hard hitting and high flying on a thin blade of ice with little protection.

You might try rodeo events such as "bull riding", all you have to do is hold on for 8 seconds, don't sound to hard however?