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Published on July 04, 2016

Overdoing exercising in the heat can fry your brain

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, medical director of Emergency Services 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 since 2002. In 2015, he was given the Korey Stringer Institute Lifesaving Award 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 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 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 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 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.”