"During exercise in hotter temperatures, our body does this great thing called thermoregulation. Thermoregulation is the body's ability to maintain our internal temperature within a safe range," says Milton. Thermoregulation causes sweating and increased blood flow. "The two combine to cause higher heart rates to perform the same amount of work as compared to a temperate environment." Plus, these mechanisms become less effective in high heat.
When you exercise and it's super hot out, you put yourself at risk for heat exhaustion and heatstroke. "Heat exhaustion occurs when the body is unable to maintain proper blood flow to all organs and the skin for thermoregulation at the same time," says Milton. "A common symptom is to collapse or extreme fatigue or inability to continue exercising. Core temperature would be between 98.6 °F to less than 105°F at this point." Once your internal body temperature hits 105°F, you're in heatstroke territory. "[Heatstroke] is even more serious and is paired with collapse and central nervous system dysfunction (confusion, dizziness, irrational behavior, etc.) This situation requires immediate cooling."
Milton says that those with high BMI and low fitness levels are more at risk for developing heat-related illnesses. "Also, those with sickle cell trait or sickle cell disease, a condition which causes the oxygen delivering red blood cells to sickle when dehydrated or in high heat, are at higher risk as well," she says. Katrina Pilkington, a NASM-certified personal trainer, adds that those with cardiovascular or respiratory issues may also experience heat-related issues.
To stay safe, follow these tips for exercising in hot weather.
7 tips for exercising in hot weather
1. Check the weather forecast
"Exercising in temperatures higher than 91.4°F can increase the risk of heat exhaustion," says Milton. And when it's humid, it's harder for your body to cool itself. When the sweat on your skin evaporates, it takes heat away with it. "This is why humidity feels hotter than dry heat," says Milton. "Less evaporation occurs when the air is already saturated with moisture."
Pilkington, who just moved to California from Nevada, says that when living in the desert there are just some times when working out outside isn't an option. "There are months there where you just literally can't workout outside, and that's okay."
2. Take it easy
"I'm a runner and I like to be outside. So, it's okay for me to go running in the heat but I need to take it easy on myself," says Pilkington. "Because if my body is trying to get rid of heat at the same time as I'm running, it's going to feel different than it would if I'm running in cooler temperatures. I try not to do any extreme like speedwork or high-intensity training. I try to keep it easy with a lot of grace to take breaks and hydrate."
As the temperatures rise, Milton says to acclimatize yourself to the heat. "Start off with lighter workouts for a shorter duration, and slowly work up over a period of 10 to14 days," she says. "Monitor your heart rate, as you may need to reduce your workload to maintain a healthy heart rate range."
3. Stay hydrated
"When exercising outside, be sure to hydrate well," says Milton. "For every pound of weight you lose due to sweat, replace it with at least a half of a liter of water. You may need to take in up to 20 percent more fluid than usual." If you're a high-salt sweater (have sweat that burns your eyes or leaves white marks on your body) or are exercising for more than an hour you should rehydrate with an electrolyte drink. And for after those long workouts, Milton says to be sure to also consume some carbohydrates.
4. Dress properly
Pilkington says this means more than donning shorts and a tank top—you want to pay attention to the materials. "Wearing cotton, or fleece of course, or anything super heavy makes it harder for the body to get rid of heat." Look clothes made from sweat-wicking or dry-fit materials.
5. Avoid midday heat
The worst time of day to exercise is in the afternoon when the sun is straight overhead, Pilkington says. For super hot days, try to exercise early in the morning or late in the evening to avoid the sun.
6. Find a shady spot
If the sun is out when you want to exercise, try to do it in the shade. This way, you're not directly exposed to the sun.
7. Wear sunscreen
Pilkington says that it's important to wear sunscreen during your workouts to protect your skin. Not only can sunburns increase your risk for skin cancer, but the Mayo Clinic explains that sunburn decreases your body's ability to cool itself.
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