Frederick Dreier

Special for USA TODAY Sports

Thirty-one athletes died during swim portion of triathlon between 2003 and 2011

USA Triathlon reviewed deaths at sanctioned events during that time

Doctors have different opinions on why swimming has posed greater risk

Nanette Nanjo-Jones and Margaret Pometta were inseparable after they discovered the sport of triathlon in 2008. They trained together on hilly roads in San Mateo County, and at races they decorated their bicycles with colored flags and wore matching pink boas. Before each event, the two always snapped a photo together.

The photo from the 2012 Vineman Half Ironman in Guerneville, Calif., is the final image of the two together. Minutes after it was taken, Pometta, a 50-year-old mother of three, suffered a heart attack while swimming in the Russian River. She was pronounced dead a short time later.

Nanjo-Jones, 47, did not hear about her friend's death until after she finished the race, which was comprised of a 1.2-mile swim, 56-mile bike ride and 13.1-mile run.

"I was shocked, it was so hard to process," she said. "I had this guilt. Maybe it was me who made her do these races."

One year after her friend's death, Nanjo-Jones no longer blames herself. But she still doesn't understand why Pometta — an experienced triathlete who never had showed signs of heart problems — collapsed and died doing the activity she loved.

Nanjo-Jones is not alone. There has been an uptick in the number of fatalities at triathlons, and the majority of deaths involve freak heart attacks during the swim. According to a recent study conducted by USA Triathlon, 12 deaths were recorded at U.S. triathlons in 2011, and nine of the victims died from heart attacks during the swim. Of the 45 total triathlon deaths between 2003 and 2011, 31 occurred from cardiac failure during the swim.

Rob Urbach, CEO of USA Triathlon, said the number of deaths simply reflects the sport's rapid growth. Between 2003 and 2011, annual participants in U.S. triathlons grew from 193,000 to almost a half-million.

"We still feel the numbers are very low," Urbach said. "There isn't a pattern except they are happening in the water."

With triathlon season in full swing, race officials in the sport are paying close attention to the issue of water safety. Last week, the World Triathlon Corporation, owners of the Ironman races (2.4-mile swim, 112-mile bike, 26.2-mile run), announced changes geared toward increased safety during the swim portions of their races.

But the USA Triathlon study does not explain why healthy, veteran athletes such as Pometta have suffered cardiac arrest. One of two dead at the 2011 New York City triathlon was Amy Martich, a 40-year-old mother of three who was a longtime swimmer and a dedicated athlete. Andy Naylor, who lost consciousness a few yards from shore at the 2012 Ironman New York City, was a longtime marathon runner. Texas trial lawyer Ross Ehlinger, 46, had raced half Ironmans and marathons for more than a decade.

A handful of theories explaining the deaths have circulated throughout the triathlon community. Cold water can constrict blood vessels, which must then circulate high volumes of blood quickly when the body begins moving, putting serious pressure on the heart. Tight wetsuits put pressure on arteries in the chest. The choppy water and chaos of the mass swim starts — some triathlons start 1,500 or more athletes at once — can cause anxiety and send an athlete's heartbeat into overdrive.

Dr. Larry Creswell, who oversaw USA Triathlon's study, thinks the trigger could come from minor genetic heart abnormalities that were undiagnosed. The stress of exercise can exacerbate these genetic defects, causing a heart attack. He advises triathletes to visit their doctors and have an electrocardiogram.

"Sudden cardiac arrest is an inherent feature of exercise; it probably happens 10 times a day," Creswell said. "When it happens in a running race, you see someone fall over, and rescuers can get on the scene quickly. But in a triathlon swim, it's harder to identify someone having a problem."

Dr. Rudy Dressendorfer, a longtime triathlete, disagrees. He thinks the problems arise when athletes do not warm up before starting the swim. Going from a resting stage to a sprint can put pressure on the heart, and a violent escalation of blood flow can shatter capillaries in the lungs, causing pulmonary edema.

"If it was cardiac defects, then how come these victims have raced for years without symptoms?" Dressendorfer said. "There has to be another mechanism at play."

Retired professional triathlete Brad Kearns, who operates the Auburn triathlon in northern California, requires his racers to swim for at least 10 minutes in Folsom Lake before the official start of the race. Kearns said he has never had a swimming death at his event.

"The body doesn't like to go from zero to 60 in six seconds; it likes to acclimatize to exercise," Kearns said. "Some racers jump from their car into a tight wetsuit and then into a cold body of water."

But not all races have the space to allow for warming up. Some have a staggered swim format, in which athletes start in waves, not at the same time. The New York City triathlon features a staggered start, but competitors must wait their turn on a dock before jumping into the Hudson River. And at San Francisco's Escape from Alcatraz, competitors jump from a riverboat into the water.

The sport slowly is changing protocols around the swim. The World Triathlon Corporation announced it would have pre-race warmup at North American events and additional lifeguards and rest buoys along each race's swim route. It also is changing the mass start format at Ironman races in Coeur d'Alene, Idaho; Mont Tremblant, Quebec;, Lake Tahoe, Calif.; and Florida.

"We felt there was more we could do to lessen athletes' anxiety and stress before the swim," said Andrew Messick, CEO of World Triathlon Corporation.

According to Nanjo-Jones, Pometta didn't warm up before plunging into the Russian River. Because of a traffic jam and long lines at the toilets, the two barely had time to put on their wetsuits and take their final photo before the race. And Nanjo-Jones said the crowded starting line did not have space for pre-race swimming.

Therese Block, Pometta's sister, waited on the riverbank with Pometta's daughter, Nancy. She said shortly after the start, she saw lifeguards bring a lifeless body to the beach. Recognizing the wetsuit design, Block knew it was Pometta and shielded her daughter's view.

Block said her family still struggles to make sense of Pometta's death. Before it took her life, triathlon had become Pometta's passion.

"I suppose we'll never know what happened," Block said. "My sister wasn't superwoman. She was a regular Joe who did this for fun, and it still happened to her."