Exercising in the Heat

During the long, cold days of winter, we long for summer exercise: soccer in the park, a bike ride along the river, a hike in the mountains, or just a day in the garden. But when the dog days of summer actually arrive, it’s important to be prepared. Exercising in the heat can be risky if you aren't careful.

Personal trainer and marathoner Carla Branch saw the danger of heat and dehydration while running a marathon in Tupelo, Miss., in August a few years back. It was the weekend before Labor Day, Branch recalls.

"It was a hot, humid day, and we were running on country roads, and the aid stations were about five miles apart," she says. "There just wasn’t enough support."

Because she planned ahead and placed extra water along the route, Branch was fine. But many racers weren’t so lucky. "My friend started getting dizzy and staggering, and another guy had to be put on IV [fluid] because of dehydration," she says.

A large percentage of people couldn’t finish the race, says Branch.

For you, exercising in the heat may not mean running 26.2 miles. But even if you’re not planning to run a marathon, you want to be smart before embarking on a summer workout.

When taking on summer exercise outdoors, says Argyle, Texas, exercise physiologist Jaime Roberts, "we need to be aware of the increase in heat and humidity."

Typically, says Roberts, our bodies are warmer than the environment. When that begins to change, our muscles regulate heat by releasing sweat, which allows the body to cool itself. But when the body is sweating, it’s losing fluid, she says.

Heat exhaustion and heat stroke, dangerous side effects of overdoing summer exercise, come when the body can no longer sustain the pace, the heat, the humidity, or the loss of fluid.

"The body cools off by sweating," says Roberts, "and as long as you remain hydrated, the body is able to cool itself off."

When you become dehydrated, the problems start.

"If the body can no longer cool itself," Roberts tells WebMD, "it starts storing heat inside. The core temperature begins to rise and you put your internal organs and central nervous system at risk."

Signs of heat exhaustion include general fatigue, weakness, nausea, dizziness, muscle cramps, and an increase in body temperature. Temperatures above 104, an inability to sweat, acute respiratory distress, and loss of consciousness can be signs of heat stroke, which is much more severe and can lead to death.

This doesn't mean you have to abandon your quest for a great summer workout. Just follow these nine guidelines to exercise smart in the heat. But make sure to talk to your doctor about starting an exercise regimen and issues about heat and hydration.