Can Cycling Classes Cause Heart Attacks?

A study finds that one hour of this strenuous exercise produces the same bodily reactions as a heart attack.

Can you suffer from a heart attack after an hour-long session on a bike? Photograph courtesy of Flickr user Richard Masoner/Cyclelicious.

Cycling classes are all the rage these days, and for good reason. You’re practically guaranteed to break a serious sweat, and, depending on your weight, you can burn more than 900 calories in a one-hour session.

But a new study suggests that the same bodily reaction experienced during a heart attack can also occur in even the healthiest person after an intense workout. When a heart attack occurs, the body secretes enzymes called cardiac biomarkers. The same happens after long periods of strenuous exercise, like running a marathon, or in this case, during a vigorous session on the bike.

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The study, published in the Scandinavian Cardiovascular Journal, included ten healthy people around age 30. Researchers measured the participants’ cardiac biomarkers with a blood test before and after an hour-long cycling session, and again a day later. They found that one hour after the session, the amount of enzymes doubled in the participants. Two of the participants’ levels rose to the thresholds of a heart attack.

However, levels returned to normal after 24 hours, which is cause for relief, researcher Smita Duttaroy said in a statement. “This is an important difference from patients who’ve had a heart attack, where levels of the markers can remain raised for several days afterwards.”

So don’t quit that marathon training or cycling class just yet. Even though a tough workout produces the same bioreactions as a heart attack, researchers say people shouldn’t be too alarmed: “It’s probably both natural and harmless.”

Still, the findings should be kept in mind when people seek emergency treatment for chest pain, since measuring the level of cardiac biomarkers is a key factor in diagnosing a patient. Consult with your doctor before taking on long-distance running or another form of strenuous exercise if you’ve had a preexisting heart condition.