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Last month was the hottest June on record ever globally. This month, it is still scorching in many parts of the U.S. And as climate change makes extreme heat waves more common, NPR's Pien Huang asks whether we can train our bodies to be more comfortable in the heat.
PIEN HUANG, BYLINE: It's been so hot in Washington, D.C. The temperature has gotten over 100 degrees three days in a row this week, and it's hottest in the mid-afternoon.
AKIL DUNN: Boiling hot. I'm barely holding on, but we're making it work.
HUANG: Akil Dunn is just leaving the skate park. It's 2:30 p.m. He's shirtless, sweaty, and clutching a skateboard.
DUNN: You know, trying to still get in my exercise, enjoying skateboarding, but it is hot, so I only got like an hour max. And that's all I got in me.
HUANG: Dunn's been skateboarding pretty regularly this summer. He's exercising in hot, humid conditions, causing changes in his body that help him deal with the heat - sort of.
DUNN: I'm not dying, but on the inside, I'm fighting demons, so...
HUANG: That process is called acclimatization, also known as heat training. Eugene Livar is the chief heat officer for the notoriously hot state of Arizona, and he says some studies suggest there could be health benefits to getting used to heat.
EUGENE LIVAR: We see increased sweating efficiency. You see the ability to perform work with a lower core temperature and heart rate, increased skin blood flow at a given core temperature.
HUANG: Most of those studies focused on athletes and military members under controlled conditions, but it stands to reason that those health benefits could translate to people who are gradually increasing their dose to summer heat. And a big disclaimer here - Livar says that being out in super-hot weather is not for everyone. Heat-related illness is serious, sometimes deadly, and can come on quickly.
LIVAR: Everybody needs to be aware and self-evaluate and work with their health care provider, trainers and others to take in any personal considerations, right?
HUANG: That includes things like age, level of fitness and external factors like temperature and humidity, and whether they can easily go somewhere to cool down. And when people are working for long hours in the sun or otherwise exerting themselves a lot in the heat, that can also lead to heat stroke, which is a severe medical emergency when the body's core temperature gets above 103 degrees.
Still, for generally healthy people, there is a window between staying indoors and getting over exposed, where spending some time outside can actually help you stay healthy in the heat. Jason Lee is head of the Heat Resilience and Performance Center at the National University of Singapore. He says that most of the manuals on heat training focus on athletes, outdoor workers and people in the military.
JASON LEE: Yeah. The templates in the sports science literature, which I question whether is applicable to the public, it's actually continuous exposure every day, between one and two hours.
HUANG: He says that's probably too much for the general public. His advice is to take it slow and easy, with long rest breaks in between.
LEE: Exercise every other day progressively in a hot environment. So assuming Monday comes, first day of a hot season, go out for a 15-minute walk, rest on Tuesday, go for 30-minute walk...
HUANG: ...On Wednesday, rest on Thursday. You get the idea. And Lee says that gradual heat exposure will help you learn to stick to the shade, drink water when you're thirsty and slow down when you're hot. These are all things that help keep your core temperature down. But when is it too hot to go outside?
LEE: Almost everyone trying to find that magical number. Long story short, there is no magical number. I know because climatic heat is after all just one of the several factors that results in the hot human body.
HUANG: Key among those factors is how much you're sweating and whether that sweat can evaporate. So it matters what you're wearing and how humid it is. Back in D.C., Akil Dunn, the skateboarder, has reached his limit. He's headed back to some air conditioning and a smoothie, but he says he'll be back soon.
DUNN: Yeah, probably later today. Can't stay out of it that long. You know, cool down, then I got to get the second session in.
HUANG: Research shows it takes a few weeks of gradual exposure to get used to exercising in the heat and maybe just a week or so out of the heat to lose it. So while heat training might help some, it won't be a cure-all for the sudden extreme spikes in heat, which are getting more common with climate change.
Pien Huang, NPR News.
(SOUNDBITE OF NELLY SONG, "HOT IN HERRE") Transcript provided by NPR, Copyright NPR.
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