Last year around this time, a man in his early 20s came into the clinic who was experiencing chest pain and a headache and was just overall feeling awful.
He’d been working on a roof. He’d done this kind of work for years with no problem. But at that time, in June, we had a heat wave. All of a sudden, instead of a daytime high in the mid-70s, the temperature was hitting the low 90s. This long-time outdoor laborer’s body simply hadn’t had time to acclimate.
For as long as I’ve practiced medicine, I’ve known that every summer, in those first few hot days, I’ll be treating some otherwise healthy people for heat-related problems. Fortunately, this man got out of the heat as soon as the symptoms hit. After drinking some water and cooling off, he was feeling fine in a few hours.
Probably, a few weeks later, he was working in the same temperature with no such symptoms. Why?
He was acclimated, or acclimatized.
No matter how many years you’ve been working or living in the heat, your body has to reacclimate to it each year. So with sudden changes, such as heat waves, everybody suffers.
Another sudden change could be the electricity going out—taking the air-conditioning with it. That’s a disaster in my book. Or maybe you take a vacation to a hot spot. Any sudden change of heat—say 10 degrees Fahrenheit or more—will require time for your body to adapt.
You can help it along by taking certain steps. To understand why these steps work, though, you need to know how your body acclimates to the heat in the first place.
Heat Acclimation: How Your Body Adapts
When the weather gets hotter, your body starts to acclimate in a few ways.
- Your body sweats more efficiently. Four main sweat-related changes take place:
- Your body begins to produce more sweat in response to heat.
- Your body starts sweating at a lower temperature.
- The sweat has a lower salt concentration, so you don’t lose as much sodium.
- This less-concentrated sweat evaporates faster, cooling the skin quicker.
- Your metabolism decreases a little. Metabolism produces heat. Your body reduces it by putting a little more fluid into your blood. This increases the blood’s volume so that with each heartbeat, more gets pumped out. Your heart rate slows down in response, which reduces your body’s workload, decreasing your metabolism a bit.
One thing to remember, though, is your body can’t accomplish these adaptions in a split second. In fact, it takes a day or so before it even starts trying and about two weeks for the acclimation to complete. During this time, it will only know to start working on these processes if it’s exposed to a minimum of about two hours of that extra heat every day.
4 Tips to Support Your Own Heat Acclimatization
In those first few days of hot weather, you can help your body both survive and acclimate.
- Gradually build up your workload. Your body produces heat of its own. (Remember that metabolism?) The more work, the more heat. So if you work outside:
- Take it easy those first few days, and take frequent breaks.
- Remember, it only takes a couple of hours a day of exposure for your body to know it needs to start acclimating. To help trigger it to start, it’s best to accumulate at least an hour of heat exposure at a time, but shade and rest are a good thing.
- Taking advantage of air-conditioning during your breaks is encouraged.
For we who stay inside most of the time, a walk or light yard work in the coolest part of the day might start the acclimation process—or just sitting in the shade for a spell. I’ve also seen recommendations to try to keep your indoor temperature no more than about 10 degrees lower than the outside. Maybe not too practical—not to mention dangerous—if it’s 105 outside, but perhaps you could gradually turn it up a bit, at least to the low to mid-70s?
- Go topless. You lose about two-thirds of your heat from the waist up. Maybe wear a loose, breathable shirt for modesty—and to prevent sunburn. The main thing here is the dilemma of using helmets. They may be essential for safety, but they also can hold in a lot of heat. So if you wear headgear, go even a little more slowly in the heat. And again, frequent breaks to take the helmet off, when your out of danger, can help a lot. Even with a hat, try one that breathes a little, or maybe just take it off and fan every once in a while.
- Drink fluids. In order for your body to utilize sweat and use your circulation effectively, it must have plenty of fluids. Drink more water in the heat. (Unless you’re really working hard, you should be able to get enough electrolytes, like sodium and potassium, from your food.) Dehydration can especially fool you in dry climates. The sweat can evaporate so fast you never know you’re sweating. Yet, given the same temperature, you probably lose even more fluid in a dry climate than you do through the heavy sweat you feel and see in the humidity. One of the ways your body adapts to heat is by making you feel thirstier, but I wouldn’t count on that too much. Thirsty or not, you need to need to replace lost fluids.
- Stay in shape. If you’re in good physical shape, that’s a big plus since your body doesn’t have to work as hard as one that’s not physically fit to do the same activity. And fat? Well, it’s a great insulator. It holds in heat really well. Not an ideal situation if your body is trying to cool down.
The Limits of Heat Acclimation
Anyone exposed to the heat can have a heat-related illness, but some of us just can’t acclimate as well. For babies, those of us in our 60s and older, and people who have a chronic disease or take certain medications, try as they may, our bodies may just not acclimate well. We’re at extra risk and need to take extra precautions to try to stay cool.
Have you ever been caught off-guard by the heat? How did it affect you?
A previous version of this article was published July 8, 2015.