South Florida heat and humidity climb to new highs. Is it too dangerous to exercise outside? –Sun Sentinel

South Florida heat and humidity climb to new highs.  Is it too dangerous to exercise outside?  –Sun Sentinel

Edith Thomas starts her day with a morning walk, right around the time the sun rises. But lately, the 80-year-old Boca resident has been rethinking her routine with temperatures that force her to stop every few blocks and rest.

“It’s so insanely hot,” she said.

South Florida has been both hotter and more humid than usual this summer with local meteorologists repeatedly announcing “the big story is the heat” as they show “feels-like” temperatures that surpass 100 degrees.

In a state with gorgeous beaches and parks, Floridians like to take advantage of running, walking, biking and playing sports outdoors. In addition, exercising outside has health benefits: It can help ward off depression and anxiety because sunshine naturally increases serotonin, a hormone that affects your disposition. “It’s a natural mood lifter,” says John Stout, a Broward County fitness and lifestyle coach.

Exercise itself, even something as simple as walking at a slow pace, produces endorphins, another feel-good hormone that boosts your mood.

The disorder, however, is heat exhaustion can come on fast and quickly progress to heat stroke, a life-threatening condition that occurs when your core body temperature reaches 104 degrees. On football fields or at boot camps, anyone exercising outside this summer needs to be aware of the risks of reaching a point where the body is unable to cool down.

An added danger in South Florida is its high humidity levels. When the humidity is high, your sweat can’t evaporate as easily and your body struggles to cool itself, making you prone to heat exhaustion and heatstroke.

“The humidity actually makes you sweat less but it feels like it’s more because the sweat is not able to evaporate off the skin,” said Dr. Cory Harlow, an emergency physician at West Boca Medical Center who has treated patients for heat-related illnesses . “It’s dangerous because you are not effectively cooling yourself.”

Local doctors say no one should be exercising in South Florida’s summer heat between 10 am and 5 pm

“If you want to exercise after 10 am, don’t do it outdoors,” Stout said. “Especially if you are over 50. Some younger people, particularly athletes can handle the heat, but when you are older, safety is most important.”

Research shows older adults can’t adjust to sudden temperature changes as fast as younger people and are the most vulnerable when the heat rises.

Dr. O’Neil Pyke, chief medical officer at Jackson North, said when the sun is most intense mid-day, you are much better off with indoor exercises such as using a treadmill or stationary bike, taking group fitness classes, or even taking up swimming.

Pyke recommends making a switch for the summer, using it as an opportunity to explore something new. “There is no way your body will not be affected if you are out there in the hot sun. But the heat should not stop you from doing exercise at home.”

Free apps, such as Nike Training Club, MyFitness Pal and Daily Yoga, offer tailored workout routines you can do at home. And some people have taken up using household items, such as textbooks and soup cans, for exercise equipment.

Michael Zourdos, professor and department chair of Exercise Science and Health Promotion at Florida Atlantic University in Boca Raton, said even as a marathon runner, he has changed his exercise time to 4:30 am during the summer and toned down his speed. “I also don’t worry about my pace in the summer. I notice that my heart rate in 80-degree heat and 90 percent humidity is higher than in January when it’s 60 degrees and low humidity. The heat definitely affects your performance.”


Hydration is critical when exercising outdoors. Stout says you should start drinking fluids before you exercise, like two to three hours before. He recommends water with lemon.

If you are going to exercise at night, you can increase your body’s hydration level by eating water-rich foods throughout the day such as cucumbers and watermelon.

During exercise, Stout recommends against quenching your thirst by gulping water or Gatorade. “Sip on it. Don’t guzzle because that upsets your stomach and can cause cramps.”

You’ll need to hydrate initially with roughly two to three cups or about 20 ounces of water within two hours before the start of outdoor exercise, and then, seven to 10 ounces of water for every 10 to 20 minutes of activity, says Zourdos at FAU.

“It’s so important to make sure you are hydrated before you do outdoor exercise,” he said. “You can’t play catch up after you get started. That’s a bad idea.”

Stout, who holds group outdoor classes at Central Park in Plantation, says the instant you feel dizzy you need to pause.

Here are some signs that you are experiencing heat exhaustion or heatstroke:

  • Nausea or vomiting
  • High body temperature (103 degrees F or higher)
  • Hot, red, dry, or damp skin
  • Fast, strong pulse
  • Lightheadedness, or passing out

Harlow at West Boca Medical Center said warning signs may be incremental.

“It could start off with muscle cramping and weakness, and then you’re sweating becomes less efficient and you get heat cramping. That’s the beginning of a slope towards danger,” he said. “As your body gets more overloaded, it goes to heat exhaustion and you feel lethargic, confused and your overall ability to function gets degraded.”


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The next stage is more dangerous, he said. “It progresses to heat stroke and organ system failure, where you will have vomiting and significant confusion. It can go from mild to severe rapidly, within 20 to 30 minutes depending on your level of exertion and the temperature around you.”

To warn that progression, Harlow recommends having someone with you rather than exercising outside alone and making them aware if you have any warning signs.

Regardless of how often or intensely you exercise the rest of the year outdoors, experts advise you pull back during summer.

“If you normally run four to five miles no problem, when it’s hot and humid, cutting back to two to three would be better,” Harlow said.

Zourdos at FAU said another option is working out more intensely indoors a few days a week and less intensely outdoors once a week. “It doesn’t have to be all or nothing.”

If you are heading outside to exercise, feel overwhelmed by the heat, and have second thoughts, don’t go, he said. “If you are exercising for your health, why risk your health?”

Sun Sentinel health reporter Cindy Godoman can be reached at


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