DENVER - Below zero temperatures did not keep a group of runners from braving the chill and risking frostbite.
The Runners Roost run club meets on Wednesday nights. With temperatures around five below zero during their 6 p.m. run, a group of about one dozen runners still met up for the weekly run.
"My hands, I think, will probably be pretty cold," said runner Sean Wetstine.
To find out just how quickly your body loses heat, 7NEWS used a thermal imaging camera to record Wetstine's body heat inside before his run, then again during his run and once more when he finished.
Before he went outside, we tested the temperature of his face, fingers and toes.
TEMPERATURE BEFORE GOING OUTSIDE:
-Face: 84 degrees
-Fingers: 81 degrees
-Toes: 60 degrees
As soon as Wetstine walked outside to prepare for his five-mile run, we checked his temperatures again.
TEMPERATURE IMMEDIATELY AFTER STEPPING OUTSIDE:
-Face: 77 degrees
-Fingers: 65 degrees
-Toes: 30 degrees
The temperature of the toe-area on his shoes dropped from 60 degrees to 30 degrees.
After about 15 minutes of running, we caught up to him to check his temperatures once more.
TEMPERATURE AFTER RUNNING 15 MINUTES:
-Face: 60 degrees
-Fingers: 45 degrees
-Toes: -19 degrees
"OK, that explains why my toes feel cold," said Wetstine. "That's crazy. I had no idea that they were that cold."
However, by the time he finished running after 43 minutes, his body actually started to heat up.
TEMPERATURE AFTER RUNNING 43 MINUTES:
-Face: 73 degrees
-Fingers: 60 degrees
-Toes: -5 degrees
"My hands actually feel pretty good too, they're slightly cold, but…," said Wetstine.
His jacket measured a temperature of 18 degrees, but when he unzipped it, the thermal imaging camera revealed his shirt underneath measuring 50 degrees.
Other runners didn't need the thermal imaging camera to reveal how cold they were. Wetstine's wife, Laura, ran in with frosted eyelashes.
"I knew they were frozen. I could see them; they were white butterflies flashing around. Luckily your eyelashes don't feel cold," said Laura.
A few of the men finished with frosted beards.
"I couldn't feel my lower jaw. I couldn't really feel my upper lip. I just knew that it was freezing up," said runner Douglas Tisdale, Jr.
When asked why he would run in below zero weather, Tisdale summed it up like a runner.
"Why wouldn't I? It's a perfect night for running, are you kidding me?" said Tisdale.