Assumption of the risk hypothetical

Take a look at the first 5 seconds of the video below (the rest of it is the same scene repeated way too many times). Assume the runner in the video had signed a waiver that says "the participant waives all rights to sue the marathon organizer or its sponsors for damages suffered during, or in any way related to, his or her participation in the race." Assume that the mat on which he slips was placed there by the marathon organizer and that experts will argue it was too slippery. Also assume the runner suffered an injury to the back of his head from hitting the ground, that he is a professional runner who makes a lot of money running marathons around the world and that he won't be able to compete again for some time. Should the court dismiss the claim based on the affirmative defense of express assumption of the risk?