...The 40-to-60-year age bracket ... now holds 32 percent of the membership in USA Triathlon, the sport’s official governing body in the U.S. More fitness conscious than previous generations, their numbers in competitive races are swelling, along with their risk of cardiac arrest. Triathlons, the most robust of endurance races requiring swimming, biking and running, are also believed to be the most risky.“People need to understand that they’re not necessarily gaining more health by doing more exercise,” said David Prior, a cardiologist and associate professor of medicine at the University of Melbourne. “The attributes to push through the barriers and push through the pain are common in competitive sport, but that’s also dangerous when it comes to ignoring warning signs.”While benefits of exercise are well-known, researchers now suspect that there may be a point at which exertion becomes dangerous, especially for middle aged men who, because of gender and changes that accompany aging, are more susceptible to cardiac arrest caused by vigorous exercise....Triathlon Risk
The death rate for triathlons is about twice that of marathons because of increased intensity of the competition and the initial swimming leg of the events, according to a 2012 study published last year in the journal Mayo Clinic Proceedings.“The swim seems to be a particularly dangerous time,” said Andre La Gerche, a cardiologist at Melbourne’s St Vincent’s Hospital and marathoner. “Paradoxically, in the marathon, it’s the opposite: it’s the last mile of the event where the vast majority of fatalities occur.” Researchers speculate that sprinting to the finish produces a rush of adrenalin that may trigger an abnormal rhythm in runners with susceptible hearts....Causes of cardiac events in athletes vary depending on age. For those under 35, cardiovascular conditions are usually inherited. Heart incidents in older athletes can be due to coronary artery disease that they don’t know they have, Melbourne cardiologist Prior said.Vessel Disease
By middle age, most people have developed some underlying early stage vessel disease, such as hardening or plaque buildup in their coronary arteries, said Kade Davison, who teaches clinical exercise science at the University of South Australia in Adelaide.“If anyone is going to have a cardiac event they’re far more likely to have one during exercise,” said Davison. A person is seven times more likely to have a heart incident while exercising than at rest, he said, citing a 1984 New England Journal of Medicine study.A person’s electrolyte balance changes while doing long distance endurance events like marathons or long cycle rides, Davison said. People might also suffer potassium or sodium depletion, or become dehydrated, which also contributes to extra stress on the heart.Heart Tears
Intense exercise for periods longer than one to two hours can cause over-stretching and tiny tears of the heart’s tissue, said James O’Keefe, a sports cardiologist and head of preventative cardiology at the Mid America Heart Institute in Kansas City, Missouri. This type of repeated injury over years can cause irregular heart rhythms, increased inflammation, scarring and stiffening of the arteries, he said.Athletic over-achievers tend to think that “more is better,” though when it comes to health, “moderation is almost always best,” said Mid America Heart Institute’s O’Keefe....O’Keefe advises his patients, especially those over 45, to run no more than 20 miles a week, spread out over three to four days.“That’s not to say you can’t get problems when you’re under 45,” said O’Keefe. “But you’re much more susceptible when you’re over 45 because it just takes longer for your body to recover and when you hammer it day in and day out, it just takes a toll on your body.”...
