When intense exercise turns deadly
While intense exercise is often hailed as the key to longevity, a team of Simon Fraser University researchers has discovered that, for some people, intense exercise can be deadly.
The team has been studying cardiac arrhythmia, an abnormal beating of the heart that can lead to sudden unexpected death in the young (SUDY), from infants to adults under age 40.
It is found in people who carry one of several rare genetic mutations that affect proteins responsible for electrical signaling in the heart.
The team—biomedical physiology and kinesiology graduate students Colin Peters and Mena Abdelsayed, and professor Peter Ruben—previously found that cardiac arrhythmia can be triggered by changes in body temperature.
Their latest findings, published in the journal Progress in Biophysics and Molecular Biology, show that increased blood-acid levels, which occur during intense exercise, can also trigger cardiac arrhythmia.
“Blood acid increases as a normal result of exercise through anaerobic metabolism,” says Ruben. “Anaerobic metabolism creates energy when the lungs cannot provide enough oxygen to keep up with the body’s demand for energy. A by-product of anaerobic metabolism is lactic acid. Its presence during intense exercise may contribute to respiratory acidosis, an increase in acid (lactic acid, in this case) in the blood.”
While either elevated temperature or blood-acid levels alone can increase the risk of an arrhythmia, Ruben says “exercise is the perfect storm for these people because both things happen at once.”
He advises people who participate in intense exercise to consider being genotyped if they have a family history of sudden cardiac death.
“Those who carry this genetic mutation should consult directly with their physician about safe levels of exercise,” he says. “They should also consider getting an implantable defibrillator, which can detect arrhythmia and then shock the heart back into a normal rhythm.”
He also recommends that prolonged exposure to saunas and hot tubs should be avoided.
Although the mutations are rare, he says, “one avoidable death is one too many.”
The Natural Sciences & Engineering Research Council of Canada (NSERC) provided funding for this research.
SFU researchers are also studying the other genetic mutations that cause the disease.