With hot weather comes the risk that athletes -- endurance athletes in particular -- will suffer a heat injury.
Most athletes are aware of the dangers of heat stroke, heat exhaustion and heat cramps. But fewer know about hyponatremia, a potentially fatal illness that occurs when your blood sodium levels decrease.
"The most important thing is to avoid hyponatremia," said Latrobe lawyer Tim Hewitt, 56, who is preparing to run the 135-mile Badwater Ultramarathon in July. The race starts 282 feet below sea level in California's Death Valley and finishes at the portals of Mount Whitney, 8,360 feet above sea level. Temperatures during the race could rise as high as 130 degrees.
"When you sweat, you are sweating out your electrolytes," Mr. Hewitt said. "If you replace that with just water, you're going to dilute the electrolyte levels in your body, and it's going to lead to dizziness and ultimately loss of consciousness."
Symptoms of hyponatremia also include headache, nausea and vomiting, and swelling of the hands and feet, according to the National Athletic Trainers Association, which has issued guidelines for exercising safely in the heat.
Drinking sports drinks such as Gatorade is the best way to replace lost electrolytes, but it can be difficult for an endurance athlete to carry bottles of the stuff on a long run or bike ride.
"I use little dissolvable tablets [of electrolytes]," Mr. Hewitt said. "They're kind of like Alka-Seltzer. Dissolve them in 20 ounces of water."
Taking ordinary table salt during exercise also can ward off hyponatremia, he said.
To help prepare his body for running in the heat of the desert, Mr. Hewitt said, "I run in long pants and long sleeves. I wear a stocking cap."
Joella Baker, 40, of Harmony, has competed in dozens of marathons and triathlons. She must take special care when exercising in heat because she suffers from lupus, a chronic inflammatory disease that occurs when the body's immune system attacks its own tissues and organs. Lupus flare-ups can be triggered by sunlight.
Ms. Baker started Get Fit Families, a personal training program for people with autoimmune and other chronic diseases. She has an exercise group that meets early in the morning, another that meets in the afternoon.
"How I train the morning group versus the afternoon group always depends on the weather," she said. "The first thing I look for is how folks are dressed. Looser-fitting, light-colored clothes, no cotton fabrics, and a light hat or visor are always recommended."
"Sunscreen is a must," Ms. Baker said. "Making sure your skin is not absorbing the rays of light will help you to not feel as hot."
Most important is hydration, she said.
"In the heat, I make my athletes drink every 10 to 15 minutes," Ms. Baker said. "I also have athletes measure their sweat rate to determine how much water they should drink in an hour."
Runners and cyclists should pick routes that allow them to refill water bottles along the way and that also have plenty of shade, she said.
Moira Davenport is a sports medicine and emergency medicine physician at Allegheny General Hospital and a long-distance runner who has run 10 marathons, including the famed Boston Marathon.
She beats the heat by going for her training runs either early in the morning or late in the afternoon when the sun is close to setting.
"You should wear technical clothing such as Nike Dri-FIT, which wicks moisture away from your body and keeps you cooler," Dr. Davenport said. "Don't wear cotton. It keeps moisture close to your body and gets heavier [with perspiration] as you run."
"Humidity is often worse than heat," she said. "When it's humid, it's that much harder for sweat to evaporate."
P.S. Martin, an emergency room physician at Allegheny General Hospital, teaches a spinning class twice a week, but isn't an endurance athlete like Ms. Baker, Mr. Hewitt and Dr. Davenport.
"I wouldn't start an exercise routine in the heat," Dr. Martin cautioned.
Dr. Davenport agreed. "The people who just go out and exercise when it is warm have the most trouble," she said.
The people who have the least trouble exercising in summer are those who were exercising through the fall, winter and spring, she said.
"When you start an exercise program when it's 40 degrees out, it's a lot easier for your body to adjust than when it's 80 degrees," Dr. Davenport said.
If you have waited until summer to start your exercise program, be aware that it will take you much longer than the two weeks people typically say to acclimatize yourself to the heat, Dr. Martin said. Go slowly and build yourself up gradually, he said.
Dr. Martin also stressed the importance of hydration.
"Take some water before initiating exercise," he said. "In my spinning classes, every two or three songs I have my students take a drink."
The key thing, Dr. Martin said, "is listen to your body. If you are starting to cramp up or are feeling confused or weak, you need to stop."
Jack Kelly: email@example.com or 412-263-1476.