But even well-conditioned athletes can run into problems.

About a year earlier, 30-year-old Tony Weathers of Dallas drowned while swimming across the Trinity River in the Original Mud Run in Fort Worth.

His aunt, Zenill Traylor, who primarily raised Weathers, said the University of Texas at Dallas graduate lived for fitness. He could run a mile at a fast pace, bench-press up to 400 pounds and had been swimming since childhood, she said.

Weathers was the only who didn't make it out of the river; his body was found the next morning, according to Traylor and media reports.

"We're still confounded because we just can't see how someone with his ability drowned," said Traylor, who has filed a lawsuit against the Original Mud Run.

Her lawsuit alleges that organizers failed to provide safety devices for participants to cross the river, did not have enough lifeguards and did not stop the race when notified that Weathers was missing. The company, the lawsuit says, acted with "utter indifference for the consequences."

Paul Courtaway, president of the Original Mud Run, declined to comment, citing the litigation. A response to the lawsuit denies that organizers were "in any way negligent" and says any alleged problems were a result of "third parties" over whom the company had no control.

Traylor is concerned about the oversight for such events. "Anyone who can dig a mud hole is having a race and people are getting injured. There has to be some kind of regulation, there has to be oversight."

She said obstacle course organizers must improve safety and more fully explain the risks to participants.

"They're going to have to do better," she said. "I know the hurt, and I know the sorrow. It leaves a hole in your heart that can never be filled."