As unprecedented heat waves become more common, exercisers must increasingly weigh the joys against the risks of outdoor training.

There is no simple answer to the question of how hot is too hot. A person’s ability to stay safe while exercising in the heat depends on many factors, such as age, usual exercise routine, training environment and intensity and whether that person is used to being active in the heat, said Stavros Kavouras, director of the Hydration Science Laboratory at Arizona State University.

Exercising in humid heat presents unique challenges, he said, but being active in dry heat can be just as risky. (If you’re exercising in humid heat, here’s a guide.)

Even when you’re at rest, your body produces heat – and the amount increases as your muscles burn fat and carbohydrates when you exercise. The more you work, the hotter your body gets.

If the temperature outside is greater than 90 degrees or if the sun is shining, your body will also be warmed by the environment, Dr. Kavouras said. (Although the body’s average internal temperature is 98.6, skin often hovers around 90, so temperatures higher than that will increase your risk of overheating.)

“As you add this huge external heat source, the body has to deal with that,” said Glen Kenny, a physiologist who studies the body’s stress response at the University of Ottawa.

Dr. Kavouras explained that the main way the body sheds heat is through the evaporation of sweat, which cools the surface of the skin. This happens more easily in dry heat than in humidity, but in dry heat, sweat can evaporate so quickly that you may not notice it.

“You don’t even see it and you don’t even know you’re getting that dehydrated,” Dr. Kavouras said.

During high-intensity exercise, most people lose one and a half to two liters of water per hour, although some people can. lose even more. As a person becomes dehydrated, sweat production slows down and it becomes harder to cool down. Some people are better at dissipating the heat than others. Those who exercise less regularly, who are not used to the heat, are awake, are sick or are older have more trouble keeping cool, which puts them at increased risk for heat illness, Dr. Kenny said.

People can, to a limited degree, acclimate to exercise in the heat, he added. In small study from 2019, Healthy men between 50 and 70 improved their ability to dissipate heat by 5 percent after a week of exercising daily in 104-degree temperatures. But it’s unclear how many people following a more relaxed regimen will acclimate, he said.

Try to exercise during the coolest time of day, which is often the early morning in dry, hot regions, said Dr. Jill Tirabassi, a physician with an expertise in sports medicine at the University at Buffalo. Seek shade and wear porous, light-colored clothing made of moisture-wicking material. The more bare skin the better.

Avoid cotton, which holds water rather than letting it evaporate, and backpacks, because you produce a lot of sweat around your spine that can get trapped, Dr. Kavouras said.

If you’re exercising and start to feel sick, stop, rest in the shade and remove excess clothing, Dr. Tirabassi said. “Warning signs can be subtle sometimes,” she said, but symptoms of heat illness can to include cognitive or mood changes, rapid pulse, headache, tunnel vision, dizziness, fainting, or nausea.

Feeling cold or developing goosebumps are clear signs of a medical emergency, Dr. Kavouras said. Cool down by drinking cold fluids, splashing yourself with water, covering yourself with a cold towel, or taking a cold shower. Work with a partner if either of you starts to feel sick.

Even if you don’t feel sweaty while you exercise, drink plenty of water, Dr. Kenny said. “Water is always the most important thing,” he said. The maximum you want to drink is about 1.5 liters of water an hour, which is the body’s absorption limit, Dr. Kavouras said. If you plan to do high-intensity exercise in the heat for more than an hour, consider a hydration drink with added electrolytes — minerals like sodium, potassium and magnesium that are released when you sweat — to replace what you lose, said Dr. Otherwise, you may experience cramps, dizziness and become prone to fainting, he said.

Sodium is especially important. “If you’re an athlete, especially if you’re exercising in a hot environment and you sweat profusely, you do need a lot,” he said. If nothing else, on days when you exercise at a high intensity for more than an hour, “it’s a good idea to salt your food a little more.”

If you’re exercising in high heat and your body isn’t used to it, be sure to give yourself plenty of time to rest between workouts as well. Consider not exercising every day.

“If you push your body day after day, there is a progressive impairment of your body’s ability to dissipate heat,” Dr. Kenny said. “Your body needs to heal.”

By admin

Leave a Reply

Your email address will not be published. Required fields are marked *