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Overdoing exercising in the heat can fry your brain

It was the scariest and most confusing moment of my life.

I opened my eyes and saw doctors and nurses hovering around me. I was flat on my back, and when I tried to sit up, my arms had been restrained. I quickly realized that I was in a hospital, but when I tried to speak, nothing but gibberish came out of my mouth.

What happened? Why did I feel like my brain had been fried?

Because, in a sense, it almost had been. I was a victim of heat stroke.

I had collapsed about five miles into a 6.2-mile race on a hot Florida day. Someone had quickly alerted a race official and I was given emergency treatment, which helped me make a full recovery. Soon, I was back racing again.

That kind of story is familiar to Robert Davis, MD [1], medical director of Emergency Services [2] at Falmouth Hospital, although it’s one he’d like to see less often.

Dr. Davis has been co-medical director of the New Balance Falmouth Road Race [3] since 2002. In 2015, he was given the Korey Stringer Institute Lifesaving Award [4] in recognition of his work on developing treatments for exertional heat stroke. He now serves on the organization’s board.

Named after a pro football player who died of heat stroke in 2001, the Institute [5] focuses on research and education to prevent the sudden deaths of athletes, soldiers and laborers.

“The Korey Stringer Institute is probably, hands-down, the world expert on heat stroke and heat illnesses,” said Dr. Davis.

One misconception people have is that there’s a progression from dehydration to heat exhaustion to heat stroke, he said. But, each can happen independently of the other.

Dehydration [6] is when our body tells us we’re thirsty. We’re not drinking enough water. One of the things you can look at is your urine color. Dark urine means you probably need a little more fluid,” he said.

Exercise-related dehydration is easy to recognize and self-treat by drinking fluids. Frequent fluid breaks will help you avoid it.

Heat exhaustion [7] is more serious, but usually doesn’t become a medical emergency.

The first sign is your inability to continue exercising at the same rate, said Dr. Davis.

“Your heart can’t pump enough blood. You can’t make enough energy. You sort of run out of gas.”

Heat exhaustion is self-limiting in that people will be too tired to continue exercising, he said. “When you stop, get out of the sun, rest and hydrate, you’ll be OK.”

Heat stroke [7] is not a continuum from heat exhaustion, according to Dr. Davis.

“Exertional heat stroke is where our bodies are unable to get rid of the heat that we generate. It’s defined by a body temperature over 104 degrees. The heart rate is increased, blood pressure might drop and respiratory rate increases.”

Heat stroke is also defined by a change in mental status, he said, which typically includes confusion, delirium or unconsciousness. (I was three for three with my Florida case of heat stroke.)

“After 104 degrees, our cells don’t work as well,” Dr. Davis said. “The proteins start to denature and people get confused. Sometimes they keep running until they pass out. If they make it to the finish line, they won’t remember the last couple of miles.”

Heat stroke is absolutely a medical emergency, he emphasized.

“It’s very dangerous. When people are above 104 degrees for more than half an hour, which can result in permanent kidney and neurological damage and even death.

“It’s very important in that situation to cool somebody down quickly in ice tubs. That’s what we do at the Falmouth Road Race, for example.”

Dr. Davis sees heat stroke more often in competitive situations, like the Falmouth race.

“What we more commonly see for the tourists or weekend athletes is heat exhaustion. Maybe they go out on the bike path or go for a run along the ocean. They kind of just poop out and run out of gas. It sort of takes care of itself once they rest and rehydrate,” he said

Acclimatization is key to avoiding health issues, now that the weather has warmed up, said Dr. Davis. Here are a few of his tips:

  • Slow down while working out when it’s hot and humid.
  • Take frequent rest breaks in the shade and hydrate well.
  • Wear loose-fitting clothing or sweat-wicking clothes.
  • Make sure you sleep well and eat well.
  • If you’ve been sick, especially with a gastrointestinal illness, you may be more susceptible to heat ailments.

Learn more about how Dr. Davis and the New Balance Falmouth Road Race medical staff assisted runners during last year’s race [8].