No, but the challenge crew knew it was raining, they knew the rain would drastically change the conditions of the course from when they tested it, and it's my opinion that they were more interested in getting the challenge done than in going through the course to see if any new hazards had presented themselves. And after having other contestants during the challenge bashing their heads against the posts and stuff, the crew could've temorarily stopped the challenge or chosen to postpone it until the conditions were safer to run.

Yes, physical injury and illness is always a risk, and Survivor challenges have been physical before. But there's a big difference between the risk of injury and endangering your contestants. They screwed the pooch on this one and more than one contestant paid the price for it.