Calgary runners are proof you don't have to hibernate when temperatures plummet. Hundreds of people bundled up Sunday to take part in the annual Hypothermic Half Marathon.

Race Director, Jacqui Allison, says just the name of the race makes most people want to stay indoors.

"We run at minus 40, so there isn't a time when we don't run. But it doesn't freeze your lungs and if you dress and cover your ears - you should always run with a buddy when it's really cold, just in case of frostbite. They can check for frostbite."

It's probably not how most would imagine spending a frigid Sunday morning, but for 4-hundred people this was a day to do what they love - walk or run 21.1 kilometres, no matter what old man winter dishes out,

Marc Morin, one of the participants in Sunday's run, says, "You do crazy things but you do what you enjoy."

The Hypothermic Half sells out every year.

Lindsay Holden explains why she takes part.

"I just wanted to be busy during the wintertime and not sit on my couch the whole winter and have something to look forward to training and everything."

But make no mistake, Allison says the race isn't easy, and it's not for everyone.

"They are very motivated and positive people and winter is embraced and not to be shut away and they don't stay in front of the TV."

Some participants could be out for up to three hours or more - a long time in frigid temperatures. But the runners claim cold weather running is not dangerous and that layering clothes is key to survival.

Bruce Covernton says if it's done properly, those layers wick away perspiration while trapping warm air near the body.

"Polar fleece tights and I've got another set of tights on, and then some pants and three shirts, a North Face jacket, toque, and wool mitts."

Medical personnel are on hand to watch for frostbite. Dehydration is a big issue too - runners don't drink as much water in the winter, even though they need it.

Still, the grueling conditions keep die-hards like Marc Morin coming back.

"This is one of the things I love, so it doesn't matter what time of day, what the weather's like, I'll do it."

And it could always be worse. Last year it was minus 38.

The Hypothermic Half is held in 16 Canadian cities. Funds raised from the Calgary run go towards the Inn from the Cold.