When the weather finally warms up, there’s no better feeling than ditching your treadmill for the great outdoors. But once the summer heat reaches sweltering temps, taking your workout beyond the gym can pose some risks. About 618 people die from complications related to extreme heat each year in the United States, according to the Centers for Disease Control and Prevention (CDC), including heat exhaustion and heat stroke. The two are similar, but have some key differences. Heat exhaustion comes down to a couple of factors: exposure to uncomfortably high temperatures over several days and a lack of fluids. This can lead to lots of sweating, rapid breathing, and a fast but weak pulse, according to the U.S. National Library of Medicine. If left ignored and your symptoms get worse, heat exhaustion can actually develop into heat stroke, a potentially deadly illness that occurs when your body temperature soars very quickly, spurring a chain of even more unpleasant symptoms. Here’s everything you need to know about heat stroke, how to spot the symptoms, and precautions you can take to keep yourself safe this summer.
What is heat stroke, exactly?
There are two forms of heat stroke, explains Luke Pryor, PhD, ATC, CSCS, the director of elite athlete performance at the Central California Sports Sciences Institute, who researches the effects of heat on athlete safety and performance.
Traditional heat stroke
Traditional heat stroke generally comes on gradually and affects very young and elderly people who have trouble maintaining their core body temperature. People who don’t have a way of cooling down—say, folks who live in a building without air conditioning—are also at risk of traditional heat stroke. In these instances, the person may not realize they’ve become hot because their body temperature is steadily rising over many hours or days.
Exertional heat stroke
Exertional heat stroke is more sudden and occurs in people who are active in high temperatures. In fact, heat-related illness can come on within hours on particularly hot and humid days. It can affect anyone exercising in the heat, but those who are doing strenuous activity—such as endurance athletes (like runners and soccer players), football players (who sweat it out in stifling equipment), and laborers (like construction workers)—face the highest risk. “When we begin to exercise, we produce an incredible amount of heat,” Pryor explains. Typically our sweat cools us down, but with exertional heat stroke, that doesn’t happen. When your organs overheat (which can occur during outdoor workouts on sweltering days) your body’s temperature-control center can malfunction. So in turn, your internal temperature rises—and when it reaches 104 or 105 degrees Fahrenheit, that’s when things start to get really dangerous. When you get that hot, the cells inside of your intestines get damaged, which can leak toxic substances into your blood and cause multiple organs to fail, Pryor says.
Heat stroke symptoms
1. High body temperature
If your body temperature hits 103 degrees Fahrenheit or higher, you could be dealing with heat stroke, according to the CDC. If you take someone’s temperature and it’s lower than that—but they still exhibit other heat stroke symptoms or feel that something is wrong—you should still do what you can to cool them down and get medical help, says Pryor. That’s because thermometers aren’t always accurate. “Someone might have a body temperature of 106, but if you get an oral temperature, they might only be 100 degrees,” he warns. “You might think they’re just a little warm when, in fact, they’re dangerously hot.”
2. Muscle cramps
Also known as heat cramps, this is one of the earliest symptoms of heat-related illness during exercise. You may experience painful spasms—particularly in your legs, arms, or abdomen—when you sweat it out in high heat. While they likely aren’t caused by the heat alone, muscle cramps do become more common when your body hasn’t acclimated to higher temperatures. Overuse and dehydration are other common causes of cramping, but if you notice this type of pain alongside other heat stroke symptoms, don’t ignore it.
3. A lack of sweat—or an abundance of it
When you spend a long time in extreme heat, your body stops trying to maintain its core internal temperature. So during traditional heat stroke (remember, that’s the kind that comes on gradually), you may actually stop sweating. However, you’ll probably start sweating like crazy if you’re experiencing exertional heat stroke. “I’ll commonly hear people say, ‘I know it’s not heat stroke because they are still sweating and that’s not true,” Pryor explains. “With exertional heatstroke, many times we see the individual well before they’ve ‘cooked’ themselves and the body is still trying to thermoregulate [maintain its core internal temperature]. If anything, you’re actually going to see the individual sweating profusely.”
4. Confusion or trouble walking
Exertional heat stroke throws your central nervous system out of whack, so a lack of coordination, confusion, aggression, or the inability to walk are huge red flags, says Pryor. “It’s kind of like a concussion where the lights are on, but nobody’s home,” he says. “They can’t answer questions appropriately, and that’s the first [signal] that we see.”
5. A pounding headache
A throbbing headache is another common sign of heat stroke. This symptom is typically due to dehydration, or the overall impact heat stroke has on the central nervous system.
6. Dizziness, nausea, or vomiting
As you continue to sweat, your body will become increasingly dehydrated. The heat will start to affect various organs, all of which can exacerbate any of the heat stroke symptoms on this list and can lead to dizziness, fainting, nausea, or vomiting.
7. Skin redness
In instances of both traditional and exertional heat stroke, the body directs blood flow toward the skin as it tries to cool itself down, making it appear red. Your skin may also feel unusually clammy or exceptionally dry, depending on what type of heat stroke you’re experiencing.
8. Elevated heart rate or trouble breathing
Your heart is put under an immense amount of stress when you overheat. Why? It needs to pump harder and faster to make sure your body’s natural cooling systems are working to keep your temperature balanced. This could lead to trouble breathing or hyperventilating.
What should you do if you think someone has heat stroke?
🚨 If you think someone is dealing with heat stroke, call 911—the situation can be life-threatening. 🚨 The best thing you can do is rapidly and aggressively cool the person down while you wait for help to arrive. Here are a few measures Pryor says you can take:
Move the person to a cooler place. Get them out of the sun and into the shade or a cool room indoors.Fill a tub with ice water and have the person soak for 15 to 20 minutes.If a tub is not available, hose them down with cold water, pour a bottle of water over their body, or take them to a nearby lake, river, or anywhere with cool water.Get them to drink water or a sports drink. This might be difficult if the person is extremely light-headed, confused, and irritable, so you might need to wait until they cool down before they can tolerate fluids.
How to prevent heat stroke
There are steps you can take to minimize your risk of heat stroke. First, make sure you drink water to quench your thirst if you are exercising in the blistering temps. Current guidelines recommend that men get at least 2 to 3 liters of water per day, while women should aim for 1.6 to 2.2 liters per day. For most people, this should be enough, says Pryor.
However, if you’ll be doing high-intensity exercise as an athlete, you should drink to match your sweat loss. Here’s how to figure that out: Weigh yourself naked and then go exercise. Afterward, wipe down the sweat and weigh yourself naked again. That difference in body weight (as long as you didn’t eat anything or go to the bathroom) is primarily going to be due to the amount of fluid you lost from sweat, says Pryor.
Convert how many pounds you lost to ounces, and that’s how much water you should drink. So, if you lost one pound of water, next time you work out, make sure you drink at least 16 ounces of water.
Another tip: Start slow and let your body acclimate as the temperature rises outdoors. Even people who are in great shape need time to work up to sweating it out in the sun. Pryor recommends decreasing the duration and intensity of your workouts for a couple of weeks. As you continue to exercise outside in the hot weather, progressively work your way back up to your normal workout. This gives your body some time to adapt so you can enjoy the weather safely.
