Understanding Windchill

The equation used to calculate the effect of wind on the human body during cold weather, or wind chill, looks like this. So to get a less complicated look at the physiological effects of wind chill, we enlisted Josh Garcia from our brainstorm team to be a guinea pig and step inside our custom lab, an ice truck. To monitor respiratory and heart rate. we've equipped josh with a high tech bioharness and an ingestible thermometer that will track his core body temperature. Alright Josh this is going to measure your core temperature. Yes It's an internal thermometer. I'm going to have you drink this water. Down it goes. For a baseline test, the truck is chilled to an ambient windless temperature of 20 degrees. At this rate frostbite could occur in as little as 30 minutes. Alright, we are about 10 minutes in and my core body temperature has actually dipped about half a degree which may not seem like a lot but it feels like a lot. Our infrared thermometer shows Josh's surface temperature is just 41 degrees. And after 20 minutes, Josh's heart rate slowly increases to above 90 beats per minute. Now, to simulate a 20 degree wind chill, We raised the ambient temperature to 31 degrees but add a 15 mile per hour wind. Josh, how are you doing up there? I've had better days, Nick. In normal conditions, the human body radiates heat which forms a layer of warm air that shields the ambient temperature from the skin, but wind blows that away making your skin more vulnerable to the cold. So although the ambient temperature was more than 10 degrees higher, the wind chill made his core body temperature fall by half a degree while areas of his skin acually dropped to below 40 degrees. But one major difference from the first test was Josh's heart rate. In an effort to maintain a safe core body temperature in cold weather, glucose stores are processed up to five times faster. This increases the body's ability to burn fat and gives the skeletal muscles fuel to shiver, both of which generate heat energy. And during the final 90 seconds of this demonstration, this causes Josh's heart rate to spike at 171 beats per minute or about 90 percent of his max. My heart is beating out of my chest. It's close to my max. This increased heart rate is what effectively keeps Josh safe while enduring the wind. I'm freezing! I really can't say I've endured temperatures this cold before in my entire life. And that process of thermoregulation, the body's effort to regulate its temperature, is a lot of work. The wind chill triggered a spike in Josh's heart rate about 25 percent higher than a cyclist during the Tour de France.