People who sign up to participate in those increasingly popular high-intensity adventure runs or obstacle races — which frequently involve getting covered in mud — might have something more to worry about than than crawling under live electrical wires or jumping into a huge vat of icy water.

According to a new report from the Centers for Disease Control and Prevention, race participants could very well find themselves wanting to remain in close proximity to a toilet for a while afterward, as at least one race has been associated with gastrointestinal infections that were linked to animal feces in the mud.

A competitor crawls through mud during Toughmudder at Phillip Island Grand Prix Circuit on March 23, 2014 in Phillip Island, Australia. (Quinn Rooney/Getty Images)

A competitor crawls through mud during Toughmudder at Phillip Island Grand Prix Circuit on March 23, 2014 in Phillip Island, Australia. (Quinn Rooney/Getty Images)

The report described 22 cases — only four of which were officially diagnosed — where participants of such an adventure run experienced fever, vomiting and bloody diarrhea. The event was in Beatty, Nevada, in October 2012 and participants frequently fell face-first into the water.

The confirmed cases were medically diagnosed as a Campylobacter coli infection, one of the most common diarrheal illness in the United States, according to the report.

The CDC’s study evaluated the nearly two dozen reported cases of gastrointestinal issues seen in both active military and civilian race participants and found a statistically significant association between ”inadvertent swallowing of muddy water while competing” and Campylobacter infection.

In light of their findings, the CDC thinks race organizers should more specifically warn participants about the hazards that could be in muddy water. (Quinn Rooney/Getty Images)

In light of their findings, the CDC thinks race organizers should more specifically warn participants about the hazards that could be in muddy water. (Getty Images/Quinn Rooney)

Now, when you sign up for one of these races, you sign a waiver that seems to cover all the bases of injury and illness, including death. Here’s an example from the Tough Mudder’s waiver (emphasis added):

I further understand and acknowledge that any of these risks and others, not specifically named, may cause injury or injuries that may be [categorized] as minor, serious, or catastrophic. Minor injuries are common and include, but are not limited to: scrapes, bruises, sprains, nausea, and cuts. Serious injuries are less common, but do sometimes occur. They include, but are not limited to: property loss or damage, broken bones, fractures, torn or strained ligaments and tendons, concussions, exposure, dehydration, heat exhaustion and other heat-related illnesses, mental stress or exhaustion, infection, vomiting, dislocations, hyperthermia, hypothermia, anemia, electrolyte imbalance, loss of consciousness, syncope, dizziness, fainting, seizures, electric shock and/or injury, and neurological disorders/pain. Catastrophic injuries are rare; however, we feel that our participants should be aware of the possibility. These injuries can include but are not limited to, permanent disabilities, stroke, single or multiple organ failure or dysfunction, physical damage to organs, spinal injuries, paralysis, heart attack, heart failure, blood cell disorder, brain swelling, and even death.

Even with the waiver though, the CDC suggests that health agencies and race organizers should further warn participants of the consequences of accidentally swallowing water they might come in contact with on the course.

“Warning participants in outdoor sporting events who might be exposed to fecally contaminated water or slurry that potentially serious diarrheal disease can result if ingested, even inadvertently, could reduce exposures to these pathogens. Event organizers should consider including the risk for waterborne outbreaks in their participant waivers and advise participants to avoid drinking or swallowing unsafe water,” the CDC’s report said.

If you think you can make it through such a race without inadvertently ingesting some of the water, you’re probably kidding yourself.

“I can confirm that it’s very difficult to do even a 5K without getting water or mud on your face, if not in your mouth,” Lenny Berstein,who has participated in one of these adventure runs, wrote for the Washington Post.

(H/T: Gawker)