Why Are Triathletes Dying?
Credit: Hannah Johnston / Getty Images

At last August's Ironman U.S. Championship in New York, a 43-year-old Hong Kong man was pulled from the water near the end of the 2.4-mile Hudson River swim and died a short time later.

"It's terrible," says John Korff, of New York Ironman. "As an event organizer, it changes your life. You just try to make it safer and warn people."

Over the past nine years, 43 competitors have died in USA Triathlon–sanctioned events – six this year alone. While the situation is not epidemic (odds of death are one in every 76,000 participants), it caused enough alarm last year to prompt USA Triathlon to convene an investigative panel, whose findings were released in September.

One key factor is clear: The event's growing popularity has increased the odds of tragedy. Triathlons now draw more than 450,000 racers a year, up from just over 64,000 two decades ago. "It's a law of averages," says USA Triathlon's Chuck Menke. "The more people who participate, the more incidents like this could occur."

The bulk of triathlon deaths, including one at a Vermont event just days after the New York Ironman, have taken place during the swim. But their causes are difficult to pin down. About 1.4 percent of triathletes suffer from swimming-induced pulmonary edema (SIPE), a potentially fatal condition in which blood leaks into the lungs, causing oxygen deprivation and, in extreme cases, cardiac arrest. Several years ago, Katherine Calder-Becker, then 43, was diagnosed with SIPE after she experienced shortness of breath and "a wet, rattly cough," foam spewing from her mouth, during the swim of a Lake Placid triathlon.

Calder-Becker believes that SIPE is brought on by a combination of factors: tight wetsuits, often frigid water temperatures, and the thrashing chaos of the swim. "You're being pummeled by several thousand people," she says. "It's a violent thing." (Since at least 1992, USA Triathlon has sent swimmers into the water in stages in an effort to combat this underwater bedlam.)

But doctors attribute most of the recent triathlon deaths to pre-existing – and often undiagnosed – heart conditions, such as hypertrophic cardiomyopathy (HCM), a thickening of the heart's ventricles. "The most common finding is an unknown heart problem, which would predispose an athlete to having sudden arrhythmia on race day," says Dr. Lawrence Creswell, a heart surgeon on USA Triathlon's panel. "For many athletes, the swim is the most stressful part of the race for the heart."

As a result, athletes are advised to undergo a rigorous physical before competition. The American Heart Association recommends a 12-point screening that checks for heart murmurs, chest pain from exertion, and Marfan syndrome, an affliction that weakens the body's connective tissue and can affect the heart. Calder-Becker, now a leading SIPE-awareness advocate, suggests athletes warm up by jogging to the race site or doing jumping jacks or pushups at the start. "It gets blood flowing and prepares the heart for what's coming," she says.

Even these precautions aren't 100 percent foolproof, however. "In a triathlon, you're pushing the body to extremes," says Dr. Bruce Lerman, chief cardiologist at New York–Presbyterian Hospital. "It's an occupational risk you have to accept."