LAGUNA PROVINCE, Philippines - Natural and man-made obstacles studded the course of a Philippine race, but the real danger to the thousands of runners came from the hordes of "zombies".
About five thousand people dashed along the five km (three mile) course of the survival-themed race in Laguna Province, about 38 km south of Manila, dodging an assortment of the walking undead in the contest based on a popular US race.
Two hundred actors dressed as post-apocalyptic zombies hid behind trees, bushes and rocky uphill climbs along the five km (three mile) course to surprise the unsuspecting runners and symbolically feast on their brains by stealing flags attached to the runners' waists.
Once all three flags were stolen, runners were "dead." But they could gain additional flags by carrying out optional tasks that often involved zombies guarding the various prizes.
Organizers said the races helped both amateur and professional runners stay focused without the boredom that can kill some runs.
"We like watching zombie shows and it really tickles our imagination," said Angelo Cruz, organizer of Outbreak Manila, which seeks to promote fitness through the races and plans to hold similar events in the coming months.
"Right now, to have it in reality, it's making everyone's summer - I hope."
There were two different routes available, trading difficulty with length to the finish according to the runner's skills and preference.
To keep both runners and zombies safe from injuries, organizers imposed a rule that forbade the zombies from any physical contact with the runners aside from taking their flags and scaring them witless.
Not all of the zombies, many well known from popular television shows, movies or music videos, used crude fright techniques.
One, from Michael Jackson's "Thriller" video, danced to trick runners into letting down their guard, at which point it snatched their flags.
At the end, runners were awarded prizes for their struggle and tried to express their feelings about surviving a global zombie takeover and what might be needed.
"The well-trained surely have higher endurance," said Rodson Santos, a university student who wore a robot costume as his way of surviving the zombie hordes.
"If you can outrun the zombies, then you'll probably survive. But if you're just a regular person without any exercise, chances are you will be easily caught."
Others drew even harsher lessons from the experience.
"In a zombie apocalypse, I guess it's all about thinking about yourself and your survival," said runner Carlos Cang.
"I mean, even if you're with friends, it's all about you. Because, you know, once you die it's all over."