Study: Triathlons can pose deadly heart risks on Yahoo! Health:
"Statistics show that for every million participants in these 26.2-mile running races, there will be four to eight deaths.
The rate for triathletes is far higher — 15 out of a million, the new study shows. Almost all occurred during the swim portion, usually the first event.
'Anyone that jumps into freezing cold water knows the stress on the heart,' said Dr. Lori Mosca, preventive cardiology chief at New York-Presbyterian Hospital and an American Heart Association spokeswoman. She had no role in the study but has competed in more than 100 triathlons, including the granddaddy — Hawaii's Ironman competition....
'It's quite frightening — there are hundreds of people thrashing around. You have to keep going or you're going to drown,' Mosca said."