Heat Stroke
Credit: Thomas Barwick / Getty Images

There's a rather cynical debate brewing in the scientific community as to whether you're more likely to die of heatstroke or cardiac events while out for a long run. The reason for it: A recent study published in the Journal of the American College of Cardiology concluded that in warm climates, runners in endurance races are 10 times more likely to die of heatstroke. This goes against the findings of a previous study in the New England Journal of Medicine, which found only one death from heatstroke and 42 from cardiac events out of over 10 million runners. Unless you're looking for an excuse not to run, the debate misses the point, which is that heatstroke is an indisputable threat to runners — and one that can be prevented.

"Heatstroke is relatively prevalent and unexpected, meaning that it can happen in any type of weather to any type of runner," says cardiologist Lior Yankelson, lead author of the JACC study. That's because of exertional heat stress, which can lead to heatstroke even on pleasant days if you don't slow down, says Dr. Brent Ruby, Director of Montana Center for Work Physiology and Exercise Metabolism. "Exertional heat stress causes runners to sort of back out of their ego, and let your mind tell you to slow down, get in the shade, or get water on top of you," he says. "Of course, most people that are competitive override that."

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When a runner begins developing complications from heatstroke, they'll at first feel mildly disoriented, weak, and can experience nausea and vomiting. When heatstroke occurs, it's generally followed by rapid collapse and needs to be treated immediately. "Heat injuries are 100 percent preventable," says Ruby. "The things that get in the way of heat injuries being preventable are your ego, your coach's ego – just dumb practices, and inexperience." 

Five Ways to Avoid Heatstroke

1. Know your limits. "It's very important that every runner knows their personal physical degree of fitness," says Yankelson. "One of the signs that something is wrong – and you should probably be stopping – is when you're experiencing a bad feeling or sensation that is disproportionate from the usual feeling that you have for that type of effort."

2. Drinking more water is not the solution. "There's this underlying misconception that if all you do is drink what you lose so that your body stays in balance, then you'll be protected from heat stress," says Ruby. It doesn't.

3. Be aware of your environment and adjust accordingly. Both Ruby and Yankelson stress the importance of acclimatizing to the climate in which you'll be running. If you're going to a destination race where the weather is warmer, be sure to spend more than a week letting your body adjust to the temperature. "The thing runners need to watch out for, the most basic thing is – don't try to perform at the same metabolic rate, or pace, while you're running in the heat if you're not used to that heat," Ruby says. "You can't compare your normal training environment with a very hot environment."

4. Consider not racing if you've been sick in the last week. Runners who have experienced any type of sickness in the seven days prior to a race, especially fever, are more vulnerable to heat stroke and should reconsider participating in an endurance event, Yankelson says.

5. Slow down. "If you feel hot, you probably are. And that's a surefire signal that you need to slow your work rate down," Ruby says. "Reducing your pace as a runner is the single best thing you can do."