(BOSTON) — The Boston Marathon kicked off Monday morning under cloudy skies, but organizers have warned runners to put health before hustle as the temperature approaches 80 degrees.
The fiery forecast prompted an unprecedented offer to 27,000 runners that spent the last year qualifying and training for the event: a deferment.
Runners keep cool by sweating. But heat and high humidity impede the body’s cooling process, according to Dr. Corey Slovis, chair of emergency medicine at Vanderbilt University Medical Center in Nashville, Tenn.
“In temperatures above 70 degrees, the body begins to lose its ability to cool itself. And once the temperature hits 80 degrees, people begin to suffer heat illnesses, such as heat exhaustion and heat stroke,” Slovis said.
Runners with heat exhaustion might feel faint or dizzy, and have a headache or muscle cramps. If they don’t take it easy, the condition can worsen to heat stroke, a serious heat illness marked by a 104-degree body temperature causing confusion and even the loss of consciousness.
Staying hydrated can help stave off heat illness. But drinking too much water can cause a dangerous imbalance in sodium and other electrolytes.
“It’s probably best to drink a combination of water and dilute sports drinks,” Slovis said. “Mixing and matching is a great way to go.”
Slovis said marathon runners would normally acclimatize themselves to heat in advance of a hot race to avoid heat illness.
“But it shouldn’t be this warm so early in the year,” he said, explaining that many runners haven’t had the chance to train in 80-degree weather. “I very much hope that people do well and we don’t see a lot of it.”
The Boston Athletic Association said it’s prepared for medical emergencies along the 26-mile course. But runners should listen to their bodies and bow out before they need emergency care, Slovis said.
“Trying to run through a cramp or knee pain is one thing. But if people start to have difficulty concentrating, difficulty with vision, or start getting a chill in the heat, it’s time to pull over to rest, drink and consider whether you want to continue walking or stop altogether,” he said.
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