INDIANAPOLIS - In the prime of her career, WNBA star Tamika Catchings found herself growing inexplicably sluggish and struggling to keep up during games. Sleeping in and eating bigger meals didn't give her any extra energy.

"I'd go to sleep tired, I'd wake up tired," said Catchings, who had a battery of tests last year to find out what was wrong.

Doctors surprised the 6-foot-1 Indiana Fever player with their diagnosis: She had asthma, a condition worsened by her strenuous job as a professional athlete.

They prescribed the 25-year-old a buterol inhaler last spring to aid her breathing by opening her constricted airways. It worked, and months later Catchings helped rally the U.S. women's basketball team to win Olympic gold in Athens.

So many people - both recreational athletes and professionals like Catchings - are being diagnosed with exercise-induced asthma that the nation's largest group of athletic trainers has drawn up its first guidelines for dealing with the condition.

The National Athletic Trainers' Association's asthma guidelines, released Tuesday during its annual meeting in Indianapolis, are aimed at familiarizing trainers, health professionals, parents and coaches with asthma's symptoms and treatments.

Asthma sufferers face shortness of breath during and after their workout routines, which can trigger an acute narrowing of the airways, making breathing difficult and causing chest tightness and pain.

Untreated, it can be fatal, although deaths are not common.

The Dallas-based trainers association's asthma guidelines include more than 20 points spelling out how to recognize its symptoms and how to help athletes manage their asthma, such as avoiding allergens by practicing indoors.

The detailed recommendations will be published in September in the Journal of Athletic Training.

"Athletic trainers are in a unique position to spot athletes' breathing difficulties," said Michael Miller, director of graduate athletic training at Western Michigan University in Kalamazoo, Mich. "They're the people who are in the training rooms, the practices and on the game fields."

About 20 million Americans have been diagnosed with asthma, with about 5,000 deaths annually, according to the American Academy of Allergy Asthma & Immunology. However, the academy estimates up to 38 million Americans may suffer from symptoms of exercise-induced asthma.

Miller, who led the task force that developed the guidelines after studying scientific literature and consulting experts, said although overall rates of asthma have more than doubled since 1980, doctors aren't sure why.

Asthma attacks can be sparked by exercise, cold air, stress and viruses, but about 60 percent are triggered by allergens ranging from pollen to pet dander.

Dr. Christopher Randolph, a Waterbury, Conn., allergist who is the former chairman of the American Academy of Allergy, Asthma and Immunology's sports medicine committee, said an estimated 30 percent to 40 percent of Olympic athletes either have asthma or symptoms consistent with asthma.

He said the reason for that is a matter of simple mechanics.

Not only do elite athletes inhale up to 200 liters of air a minute in the heat of competition - compared with 3 liters a minute for the average person at rest - they're also breathing big gulps of air through the mouth, Randolph said.

As a result, cold or dry air and allergens enter their lungs without being warmed, moistened or filtered by the sinuses, increasing the risk of constricted airways.

"Once you understand that, you can easily understand why they're much more likely to show signs of asthma. They're inhaling much more than the rest of us," he said.

Dr. John Weiler, a professor emeritus of internal medicine at the University of Iowa who has studied exercise-induced asthma for more than 20 years, said many athletes keep their asthma secret, fearing it could hurt their chances of a professional career.

"A guy who's played four years of football at state college and is looking at the NFL, it just isn't something he wants to (let) get out," he said.