KNIGHTSTOWN, Ind.—Daniel Smith had run over hills, scrambled through streams and climbed over walls on a recent hot Saturday here, when he came face-to-face with his greatest obstacle yet: a field full of zombies.
He dodged through about 20 groaning, glassy-eyed antagonists with oozing facial wounds and streaks of red splattered across their clothes. "I felt like it was just nonstop sprinting for my life," said the 18-year-old from nearby Yorktown.
Mr. Smith, who runs high school track and cross-country, paid $87 for the privilege, while the zombies chasing him paid $25—and got a free makeup job and, for those over 21, a complimentary beer at the end of the race.
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Obstacle-course races and zombie-themed events—from proms to marches to film festivals—have been spreading across the country like a flesh-eating bacteria. Now, a series of races called "Run For Your Lives" are bringing the two together.
Runners wade through pools of fake blood, duck under electrified wires and try to avoid letting zombies steal their "health flags" worn on a belt around the waist. A runner with no flags left is ruled dead—or is it undead?—and isn't eligible for awards at the end of the five-kilometer race. Crossing the finish line alive is no small feat: Only about 20% of racers make it with at least one of their three flags left.
Mr. Smith had managed to hold on to his flags through several close encounters with zombies when he suddenly found his path blocked by a pair of female twins in checkered blue-and-white dresses, their faces bruised and heads cocked to one side. "They looked sort of demented," he said.
He dodged to the side and into a shin-deep creek to pass them, but lost his first flag to a grasping hand.
Zombies come up with their own outfits, but organizers do their makeup, including pale skin, sunken eyes and fake blood—a mix of corn syrup, cornstarch and food coloring—splashed on their clothes. Adhesive plastic molds and red goo give some zombies gaping wounds.
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Zombies preparing for the race here lined up to stand in front of a hanging white sheet and have a makeup artist throw handfuls of blood on their backs and chests before they set out to populate a 70-acre course rigged with water pits, log barriers and monkey bars.
"That felt really good because it was hot out," said Michael Packer, who drove 45 minutes from Indianapolis with his girlfriend and two other friends—all wearing surgical gear. "It soaked through pretty well and it stayed wet for a long time."
Reed Street Productions, a company based in White Marsh, Md., and formed by two friends in their 20s, is making a killing on the races. It held its first race just last year near Baltimore and unexpectedly drew 12,000 people, the company said. It will hold a total of 13 similar events in cities from Boston to Los Angeles this year. Next year, it hopes to double that. The company said it expects revenue of $18.8 million this year, but declined to disclose its profits. Between 3,000 and 10,000 people participate in the races, with about 5,000 at the event here.
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"Why a zombie race?" asked Derrick Smith, co-founder of the Run For Your Lives races and no relation to Daniel Smith. "We came up with the name, and we said, 'Well, what do people run from?' We figured zombies was going to be a pretty popular idea," he said.
Indeed, zombies seem to be everywhere these days, including on television. AMC Networks Inc.'s apocalyptic zombie drama "The Walking Dead" has drawn millions of television viewers.
Zombies in the Run For Your Lives races are split into two groups. "Chasers" run after racers to grab their flags, while "stumblers" are supposed to "crawl, shuffle, drag, or perform any other type of slow movement in order to horrify runners and take their flags," according to instructions for zombies on the race website.
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Mr. Packer, a 41-year-old software designer, was a chaser. He was resting in the shade when two men dressed as Elvis emerged on the path up ahead and began jogging toward him.
He looked around as if sensing the presence of the Elvises, then reached out with his clawed hands and lurched toward them and two other runners, his back stiffly bent.
"I went for the wide-eyed, slobbering, drooling zombie growl," said Mr. Packer. His startled targets leaped into a sprint down the path to escape.
Runners Kate Christensen, a 30-year-old microbiologist from Oconomowoc, Wis., and Cindy Rasmussen, a 30-year-old biochemist from Whitewater, Wis., wore plastic hula skirts with hanging green strips that made it harder for zombies to grab their flags. And when Ms. Rasmussen lost her third flag, she started running interference for Ms. Christensen.
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"We worked together as a team and tried to use other people as bait," Ms. Christensen said.
But the zombies worked together too. Daniel Smith, the high-school runner, lost a second flag when a large group of zombies forced him to one side of a path, allowing a chaser zombie to catch up to him. He later dove into a mud hole to protect his remaining flag.
Mr. Smith continued on to a maze, where he narrowly escaped a different chaser, and climbed over a cargo net. With the finish line in sight, the race had one more surprise for him—a low, electrified fence to crawl under. Mr. Smith dropped to his elbows and started pulling himself forward.
"I looked up to look at the finish line and got zapped in the head," he said. "It stung pretty good." (Organizers later turned off the electricity when a combination of exhaustion and dehydration caused adverse reactions in some runners.)
Mr. Smith learned after he went home that he had finished with the fastest time among living finishers. His prize, which he has yet to claim, was a set of zombie paraphernalia including a keychain, a Run For Your Lives T-shirt and drawstring bag. Asked whether the prizes were worth the ordeal, he hesitated and then said: "Not that much."