“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 Australia’s 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 the benefits of exercise are well known, researchers suspect that there may be a point at which exertion becomes dangerous, especially for middle-aged men.
Cardiac arrest, which occurs when the heart suddenly stops beating, can be caused by almost any heart condition, including abnormal heart rhythm and thickening heart muscle or arteries; such changes can occur silently as healthy people age. The risk of sudden cardiac arrest, which can be brought on with physical stress, increases with age, and men are two to three times as likely to suffer from it as are women, according to the National Institutes of Health.
Michael McClintock, 55, a bank executive who died June 2 at his home in Larchmont, N.Y., was a skier, biker and golfer. Last September, he completed his first Olympic-length triathlon, taking fewer than four hours to swim 0.9 miles, cycle 25 miles and run 6.2 miles.
While McClintock’s death can’t be directly linked to the race, USA Triathlon has noted an increase in race-related fatalities, with the highest number occurring in the 40-to-49 age group.
The death rate for triathlons is about twice that for marathons because of the increased intensity of the competition and the initial swimming leg of the events, according to a 2012 study in the journal Mayo Clinic Proceedings.
“The swim seems to be a particularly dangerous time,” said marathoner Andre La Gerche, a cardiologist at Melbourne’s St. Vincent’s Hospital. “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 adrenaline that may trigger an abnormal rhythm in runners with susceptible hearts.
The swim leg of the triathlon, often held in open water, can be “extraordinarily stressful,” said La Gerche, who has competed in more than 100 triathlons. “You have people climbing all over you. Sometimes you’re fighting to breathe, and that’s not something the body is used to.”
Open-water racing triggers a clash of two mechanisms of the involuntary nervous system, according to researchers at England’s University of Portsmouth. A “fight or flight” response activated by physical exertion, cold water temperature or anxiety tries to speed up the heart rate and causes hyperventilation; this occurs just as the body tries to slow the heart rate to conserve oxygen in response to facial wetting, water entering the mouth, nose and throat, and extended breath-holding, the scientists said.
“Normally, the two responses don’t happen at the same time, but when they do, the heart can go into abnormal rhythms, which can cause sudden cardiac death,” Mike Tipton, who runs the Extreme Environments Laboratory at the University of Portsmouth, wrote in a commentary for the British Journal of Sports Medicine.
Runners should maintain their pace or slow down in the last mile and not sprint unless they have trained for it, the International Marathon Medical Directors Association said in 2010 in response to race-related sudden deaths.
Running appears to lower mortality risk when an athlete doesn’t cover more than 20 miles a week, exceed 5 to 7 mph or run more than two to five times a week, researchers at the Ochsner Health System in New Orleans and the University of South Carolina found last year.
More than 2 million Americans participate in long-distance running races each year, a number that has doubled since 2000. Even though the risk of death from running marathons is small, increased participation has resulted in a higher incidence of sudden death at the events, according to a study published last year in the New England Journal of Medicine. Of 11 million long-distance runners, 59 suffered cardiac arrest, 51 of them men.
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 as likely to have a heart incident while exercising as they are while at rest, he said.
Intense exercise for periods longer than one to two hours can cause overstretching and tiny tears of heart tissue, said James O’Keefe, a sports cardiologist and head of preventative cardiology at the Mid America Heart Institute in Kansas City, Mo. Such repeated injury over years can cause irregular heart rhythms, increased inflammation, scarring and stiffening of the arteries, he said.
Athletic overachievers tend to think that more is better, though “moderation is almost always best,” O’Keefe said.
As a precaution, getting a computerized tomography, or CT, scan of the heart to look for calcified plaque is a good way for endurance athletes to check if their workouts are putting their heart at risk, O’Keefe said. Yet there is no agreement on what the best strategy is for testing.
“The throwaway line is to consult your doctor to make sure you’re fit to race,” La Gerche said. But “in healthy asymptomatic people, there is no good test to see if someone is at risk of sudden death.”
World Triathlon, owner of the sport’s Ironman-branded events, made changes to the swim portion of select races after an increase in competitor deaths in recent years, the company said last month.
Some events no longer feature a mass swim start. Athletes at those races will either enter the water in a continuous stream through an access point, with their time starting when they cross a timing mat, or in staggered waves.
O’Keefe advises his patients, especially those older than 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,” O’Keefe said. “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.”
— Bloomberg News