July 21, 2023: Richard Carter had spent the morning picketing outside the Walt Disney Studios in Burbank, CA, with other striking actors. Now, at noon, the temperature had reached 93 F, and a hot breeze was blowing. However, Carter, a supporting actor in his fifties who tells the television show We are between her credits, she was still light-hearted.
Some might call him an “iguana,” one of those people who, like reptiles that prefer 95-degree sun, don’t complain when temperatures soar. He notices, but doesn’t stop.
“I’m like, ‘Damn, it’s hot,’” he said, then quickly adds, “I’d rather say that than ‘Damn, it’s cold.’”
Relocated from Chicago, he can still describe in detail that minus-20 day long ago, with a wind chill he said made him feel like minus 60, while waiting for a 20-minute late bus. It was then that he and his wife decided to pack up and head west. “I didn’t feel too bad today,” he said of the 90+ F heat.
In Bend, Oregon, temperatures are also hot, reaching the mid-90s. However, the weather hasn’t stopped Patrick Fink, MD, 35, an emergency physician and natural medicine specialist with St. Charles Health System, from spending a couple of hours on his mountain bike regularly. “I don’t care, and I have no problem exercising in it,” he said. “I think it’s a matter of serial exposure.”
This summer, the heat is on and it’s been hard for most of us not to notice. As of July 20, more than 100 million Americans were under heat Alerts, according to the National Integrated Heat Health Information System, a collaboration of federal partners to provide information on extreme heat risks. Cities that are usually hot, like Phoenix, are setting records this summer, hitting 110 degrees F on July 20 for 21 straight days. The world ended the hottest week on record on July 10, according to the World Meteorological Association. And there’s more heat, much more, to come, experts warn.
With extreme heat in the forecast, learning to cope with the heat is the must-have new skill. “I think we all have to learn to live with that,” Fink said, “because it’s not going to change anytime soon.”
But is handling the heat a skill or is it all genetics? Some people can cope with the scorching temperatures, while others can’t? It’s debated among experts, with some saying that people tend to have a better or worse tolerance for heat.
Genetics or not?
heat tolerance it’s likely partly genetic, said Thomas E. Bernard, PhD, a professor of public health at the University of South Florida in Tampa who studies occupational health and heat stress. Just as some people have higher natural athletic abilities than others, some of us are more physically capable of withstanding high temperatures, he said. But just as sports training can help athletes of all abilities better compete in their sports, improving aerobic fitness can help improve heat tolerance, he said.
This is why. “Heat stress is not so much a hot environment as it is that you generate heat inside your body,” Bernard said, and in order for you to cool down, that heat has to come out. Someone who is aerobically fit also has good cardiovascular fitness and is better able to dissipate that heat to the environment, he said.
Genetics probably don’t play a big role in heat tolerance, said Graham M. Brant-Zawadzki, MD, assistant professor of emergency medicine and nature medicine specialist at the University of Utah Hospitals and Clinics in Salt Lake City. Many other things affect heat tolerance, he said.
Being overweight or obese, with the added layer of insulation, can make people less tolerant of heat. Diabetes can damage blood vessels and nerves, affecting sweat glands and the body’s ability to cool itself. Certain medications, including blood pressure medications, such as diuretics, antihistamines, and psychiatric medications, can affect heat tolerance. Age plays a role in heat tolerance, and infants, toddlers and older adults are more likely to have problems with heat, Brant-Zawadzki said.
But, he said, “we are all capable of becoming more heat tolerant relative to our own baseline.”
How to train and adapt
Being regularly active in the heat can be key to tolerating it, said Fink, the emergency medicine physician who practices mountain biking. “I think I’m acclimated to the heat because I do it regularly,” he said.
Training in the heat builds tolerance, Brant-Zawadzki agreed. Do it judiciously and with his doctor’s approval, he said.
“The idea is to stress yourself out for about 20 minutes at a time and then give yourself 10 minutes to cool down.”
Do that a few times a day. This, she said, triggers a response at the cellular level, with the body producing more of what experts call “heat shock” proteins. “Making more of these proteins helps drive some of the changes that help people better cope with heat,” Brant-Zawadzki said.
Those with higher levels of these proteins hyperventilate less, for example, he said.
The CDC and the National Institute for Occupational Safety and Health call heat acclimatization “the improvement in heat tolerance that comes from gradually increasing the intensity or duration of work performed in a hot environment.” For employers hoping to prevent workers from contracting heat-related illnesses, the agencies offer a schedule. Workers gradually increase the amount of time they work in the heat, working up to 100%.
“Exposure to heat and physical exertion need to occur at the same time,” Bernard said. As you acclimate, “you start sweating sooner, you sweat more, and you lose less salt.”
Simple strategy: turn down the air conditioning
“Something that we (also) can do is decrease the level of air conditioning that we use,” Brant-Zawadzki said. “It limits our ability to acclimatize.” It’s typical for people to go from a very hot 105 degrees outside to a restaurant that could be as cold as 65 degrees, he said. That will not help increase heat tolerance.
As a general goal, he suggests keeping the air conditioning in your home or office no more than 10 degrees cooler than outside. Of course, if it’s 100 degrees, keeping the air conditioner at 90 degrees won’t help. But try not to turn the air conditioner 20 or 30 degrees colder than outside, he said.
What about the supplements?
Researchers are looking at the role of the supplement betaine, also called trimethylglycine, in improving heat tolerance. So far, it seems to help in animal studies, said Brandon Willingham, PhD, a registered dietitian and assistant professor of kinesiology at Coastal Carolina University in Conway, South Carolina, who conducted the research while at Florida State University. It may act in a similar way to heat shock proteins, he said.
But there is no evidence yet that it works in people, although research continues. “Maybe in a year, we’ll have a different story to tell,” he said.
real life strategies
Conner Ohlau, 41, of Scottsdale, AZ, works as a project manager for a commercial construction company. “I’m a project manager who works with my hands,” he said, preferring outdoor work to days at a desk and computer. One day recently, he had worked outside from 10 to 5, with the temperature reaching 117 F. He said that people often cannot believe that he works day after day in the intense heat.
He has learned to handle the heat. “I stay out of the sun, that’s the key,” she said, wearing a hat and neck warmer when the sun gets intense. “When you’re outside, you have to be able to put something cool on your neck every 15 to 20 minutes.” She also changes her shirt frequently and drinks a couple gallons of water on the hottest days. He avoids alcohol, which can dehydrate him, during the work week.