Hot temperatures make exercising outdoors a risk


In August, Drake Geiger, a 16-year-old high school football player in Omaha, Neb., collapsed and died while practicing with his team. The temperature was a scorching 91 degrees with the heat index (a blend of temperature and humidity) at 105 degrees.

According to the Centers for Disease Control and Prevention, approximately 702 heat-related deaths occur annually in the U.S. The CDC also reported an average of three student deaths a year from heatstroke.

“Coaches have to do a better job of recognizing when their players are in need of a break or water, or encourage their players to let them know when they’re not feeling well,” said Evan Williams, CSCS*D, sports performance specialist for UCLA Health Sports Performance Powered by Exos.

However, it’s not just competitive athletes that need to monitor their health while exerting themselves in the heat. Everyone who is physically active outdoors, especially when temperatures are high, needs to closely monitor how they’re feeling.

What are the risks of working out when temperatures are extremely hot?

“Heat makes your body work harder,” Williams explained. “Your body is already working hard during your exercise, but it’s also working harder to keep you cool. So, that means that your body is working double, as it is fighting against the heat to normalize your body temperature. That is normally why people feel so drained while working out on hot days.”

Dr. Brett Dolezal, PhD, director of the Airways & Exercise Physiology Research Laboratory at UCLA, explained what happens to us when we push ourselves physically in hot conditions.

“Our bodies dissipate heat through radiation and convection, which balances the excess heat produced by metabolic reactions that keep us alive. In very hot conditions, our core temperature increases, the blood vessels in our skin dilate and we begin to sweat.

“The water vapors to sweat, creating a cooling effect on the skin,” he continued. “The problem arises when it is so humid that sweat starts dripping off you instead of evaporating.”

Dr. Dolezal is referring to the sticky feeling we sometimes experience when sweat is unable to evaporate and instead stays on our skin. As a result, the body continues to produce sweat underneath that layer of sweat, leaving us uncomfortable and unable to cool down. Too much humidity can sometimes send the body into overdrive while trying to cool down, causing the body temperature to rise.

What symptoms might athletes experience from being out in the heat for too long?

It’s not just competitive athletes that feel the effects of the sun’s rays. Amateur athletes across the globe who employ the great outdoors as their gymnasium during scorching days are at risk of heatstroke.

Dr. Dolezal says athletes should pay attention to the following symptoms when out in the sun:

  • thirst
  • nausea
  • headache
  • low-grade fever
  • muscle aching or cramping

“If you choose to ignore these warning signals and keep exercising, your risk of developing heatstroke increases and this is no joke,” said Dr. Dolezal. “At this point, you are no longer able to dissipate heat and you stop sweating. Your breathing and heart rate increase, your skin gets dry and red, and your brain oxygen supply starts to be compromised. When this happens, your confusion escalates and convulsions can happen.”

When should people avoid exercising outdoors?

“Anything above 85 degrees is when I bring my clients inside,” said Williams. “You never want to risk jeopardizing someone’s health in the heat.”

Williams warned that everybody is different when it comes to heat. A person in great physical condition may be able to withstand hotter temperatures. However, anything in the mid-80s and above needs to be considered serious. Doing intense workouts in temperatures in the high 90s and 100s should definitely be avoided, he said.

Dr. Dolezal explained that if we choose to work out in hot temperatures, then we need to make sure we listen to our bodies.

“Our bodies have amazing capabilities of adapting to almost everything, but we have to listen to them and play smart. If you’re going to exercise in very hot conditions, pace yourself during the first two weeks to allow your body to adapt,” said Dr. Dolezal. “Then, track outside temperatures and play it safe in those days out of your normal range of temperature. Be hydrated and listen to your body’s warning signals.”

Pre-workout tips for exercising in hot weather

For those who choose to brave the heat, there are some precautions you should take before working out.

  • Drink plenty of water several hours before you exercise.
  • Wear apparel with hydrofreeze or dry-cooling technologies (these help you stay cool when exercising).
  • Avoid alcohol (particularly when it’s close to your workout time).
  • Monitor outside temperature.
  • Try to avoid strenuous activity during peak heat hours (11 am to 4 pm).

Take care of your body during and after workouts

If an athlete begins to feel heat-related symptoms or discomfort during a workout, he or she should stop exercising immediately and find a cool shaded area. Remove tight or heavy clothing and slowly drink cool water or some other cold non-alcoholic beverage. Placing cold packs on the base of one’s head also helps regulate the body temperature.

After a workout, athletes should drink fluids with electrolytes to replenish pH levels and to regulate heart rate and fluid levels in the blood plasma.

To learn more about exercise safety, visit the UCLA Airway & Exercise Physiology Research Laboratory.