Science Says We’re Built to Run in Extreme Conditions

It might not be what you want to hear, especially as temperatures begin to drop and sleeping in and staying warm become more tempting. But it’s true: Humans are uniquely built for running in high and low temperatures. We turned to science to help us understand a little bit more about how (and why) our bodies can push the limits when it comes to running in cold weather and running in the heat.

Some Like It Hot

While we are generally considered weaker runners than many animals, anthropological studies suggest that, during our hunter-gatherer days, humans adapted to be able to endure high-heat running in order to wear down faster prey. (This doesn’t apply just to men. Recent studies reveal that in some ancient cultures, women were also hunters.)

Lewis Halsey, from the University of Roehampton, and Caleb Bryce, from the Botswana Predator Conservation Trust, tested this theory in modern time by pitting human race data against horse race data. They analyzed results from the UK’s Man vs. Horse Marathon, the Tevis Cup 100 and Western States Endurance Run, and the Old Dominion 100. Looking at 260 humans and 350 horses, they found that hotter temperatures affected the speed of both groups, but it affected horses far more than it did humans, even with horses’ superior cardiovascular system.

Several studies examining endurance runners (conducted in a lab setting) suggest that female runners are even less affected by heat than men.

Runners who tackle the hottest races in the world where temperatures get up to 120°F (races like Marathon des Sables in Morocco, or The Speed Project and The Badwater Ultra which both cross through Death Valley) have all sorts of tricks up their sleeves to get it done. Some have been known to train in actual saunas to prepare, while others utilize gear hacks like freezing their clothing beforehand.

Bring On the Cold

On the other end of the spectrum, our ability to run can keep our core warm enough in cold-weather conditions to offset heat loss, according to a study conducted in the U.K. in 1997. As warm-blooded creatures, our body has the ability to reduce blood flow and retain heat when we need it through a process called vasoconstriction. This enables our torso to stay warm during runs in cold weather. “Because exercise generates heat as a by-product, the cold isn’t deleterious to doing exercise,” says Halsey. “Indeed, it can be a help because heat is lost from the body more quickly.”

And with the snowy, icy terrain, she had to be prepared to run in the cold for a longer time period. “Running was so different because you’re on ice covered with snow. So, you take a stride forward and sometimes slip a stride back.” She ended up as the second female finisher at 5:30:32. The current women’s record for that race is 4:20:02, set by UK runner, Fiona Oakes.

“I won’t complain about 40 degrees for the Chicago Marathon anymore,” Larson says.

Even though we have evolution and genetics to thank for the way we can adapt to harsh conditions (and proof from fellow runners that it’s indeed possible), it doesn’t mean it’s safe to go out and run in just any condition. In heat, it’s important to know about hydrating, sun protection, and the signs of hyperthermia. Likewise, cold winter weather brings its own precautions. Make sure you’ve done your research before stepping out into a potentially dangerous situation.

Larson’s winter weather advice: “Don’t stop if it’s too cold. Run inside on a treadmill, but get outside as much as possible.”