Leaping off a 15-foot-plank into a pond stopped some cold. So did sloshing through a pit filled with ice and muddy water.
But the real thorn in this curse-inducing course came in the form of 400 dangling wires pulsing with electric current. For every person who managed to run through the crackling curtain unscathed, half a dozen dropped to their muddy knees, wincing with each zap of voltage.
Think triathlons are for wimps? Meet the Tough Mudder.
A sort of obstacle course on steroids dreamed up by a 30-year-old Brit who worked in counterterrorism, the event is modeled after the most rigorous military test. Thousands converged at CrossCreek Cycle Park on Saturday to attempt it.
"Running 10 miles is not really a challenge — getting electrocuted, burned, crawling through barbed wire, carrying a log half a mile on your shoulder u2026 that is," event creator Will Deans said.
Participants shelled out up to $160 each. All they got for completing 17 obstacles on the 10-mile course was a T-shirt, an orange headband, beer — and, if they wanted it, a free mohawk haircut.
They also raised money for the Wounded Warrior Project, which supports the needs of severely injured service members.
In all, about 5,000 athletes registered for the event, which will be repeated today with new participants. Spectators can watch the chest-beating action for $15.
Some challenges required teamwork; others demanded aerobic fitness. A few, including those electrified wires, racheted up the fear factor. However, a burn ban forced organizers to drop the run through 4-foot flames.
"Is that what it's like to be Tased?" asked a mud- and mascara-spattered Megan Parsons, 30, a trainer at CrossFit Central in Austin. "That popping noise made it even worse."
Dean said he wants his event to show people what goes into training for special forces units. "Part of that is getting people outside their comfort zone mentally and physically."
Organizers seem to be proud of the event's 22 percent noncompletion rate. Participants must sign a death waiver, and signs posted on the course remind them they did.
"The tougher we make it, the more people enjoy it," Dean said.
The event is not designed to appeal to the same crowd that's drawn to traditional triathlon, the three-part sport of swim, cycle and run.
"People who want to wax their legs and practice changing socks quickly are just not going to enjoy this," Dean said.
Tough Mudders are 80 percent male and mostly in their early 30s. The average finishing time is about two and a half hours.
"I thought it was great," moaned Andrew McCullough, 42, an investor from Houston. "But I don't think I'll do it again. I'm too old for this kind of stuff."
"We need to incorporate this training into our physical fitness plan," said Sgt. Apolonio Gomez, 27, an Army infantryman stationed at Fort Hood.
The Tough Mudder series has grown from three events in 2010 to 16 this year. It's one in a spate of amped-up fitness challenges even more extreme than the adventure races that have soared in popularity in Central Texas in the past decade.
The newer events pack their agendas with Rambo-esque tasks.
In November, racers in the Warrior Dash clambered over junked cars and belly-crawled through mud. In March, participants in the Spartan Sprint Race will throw spears and tackle climbing walls. About 1 percent of the Sprint Race's competitors will qualify for the annual Spartan Death Race in Vermont. They might wish they hadn't.
"Traditional physical challenges will make giving birth look like a walk in the park," that event's website says. "Please only consider this event if you have lived a full life to date."
At the Tough Mudder finish line party Saturday, athletes sipped beer, picked up U.S. Marines brochures and rubbed sore muscles.
And, perhaps in at least a few cases, reconsidered their idea of what's fun.