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 rates, we've equipped Josh with a high-tech bio harness and an ingestible thermometer that will track his core body temperature.

All right, Josh this is going to measure your core temperature. It is an internal thermometer. I'm gonna have you drink this water and 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 his little in 30 minutes. We're about 10 minutes in and my core body temperature is actually dipped about a half a degree, which may not seem like a lot but it feels like lots. 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 raise the ambient temperature to 31 degrees, but add a 15 miles-per-hour wind.

Josh, how are ya doing up there? I’ve had better days, Nick.

In normal conditions the human body radiates heat, which force 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 actually dropped to below 40 degrees. The 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 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 ninety percent of his max.

My heart is beating out of my chest. It is 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 have endured temperatures this cold before in my entire life.

In that process of thermal regulation, 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 twenty five percent higher than a cyclists during the Tour de France.