RELATED: If You Notice This in Your Mouth, It Could Be the Sign of a Heart Attack. A 2020 meta-analysis conducted by the American Heart Association (AHA) and published in the journal Circulation highlighted the danger of vigorous physical activity, like participation in marathons and triathlons. The agency reviewed more than 300 scientific studies and found that the risk of heart attacks or other cardiac events, like sudden cardiac death, as a result of this type of exercise has risen. The risk of these is both “increased during and shortly after bouts of physical exertion,” the researchers stated. Of the studies reviewed, the AHA found that there was a 2- to 10-fold increase in the likelihood of experiencing a heart attack within one hour of participating in vigorous exertion. One study even found that the risk could persist for up to two hours after. “More people are running marathons, participating in triathlons and doing high-intensity interval training. The purpose of this statement is to put the benefits and risks of these vigorous exercise programs in perspective,” Barry A. Franklin, PhD, chairman of the AHA committee that helped conduct the study and director of preventive cardiology and cardiac rehabilitation at Beaumont Health, said in a statement. RELATED: Eating This Sweet Treat Every Day Slashes Heart Disease Risk, Study Shows. Not everyone needs to give up vigorous physical activity, however. The risk is highest and more concerning among untrained participants, according to the AHA. Per their analysis, 40 percent of cardiac events among participants in triathlons occurred in first-time participants. Those who may have an underlying or undiagnosed cardiovascular condition or have had a prior heart attack are also more at risk for experiencing a heart attack during or right after intense exercise. “Like medicine, it is possible to under-dose and overdose on exercise,” Franklin said. “More is not always better and can lead to cardiac events, particularly when performed by inactive, unfit individuals with known or undiagnosed heart disease.” Exercise is good for your overall health and that includes your heart health. According to the AHA, physically active people—like those who walk regularly—have a 50 percent lower risk of heart attack and sudden cardiac death compared to inactive individuals. Beyond that, adults who are more physically active once they reach 50 have a seven to eight year higher life expectancy. The AHA says that aerobic exercises (where large muscles move in a rhythmic manner for a sustained time) like walking, running, cycling, or swimming are great ways for people to maintain regular physical activity.ae0fcc31ae342fd3a1346ebb1f342fcb RELATED: For more health content delivered straight to your inbox, sign up for our daily newsletter. Aerobic exercises can be done at both low intensity and high intensity, but because of the risks associated with high-intensity exercise, the AHA says people should work up to that level. You can build up to this slowly without seeing a physician, unless you experience physical symptoms such as chest pain, chest pressure, or severe shortness of breath while exercising. If you experience this or have any known heart disease, you should talk to your doctor before continuing to exercise, per the AHA. “Exercise is medicine, and there is no question that moderate to vigorous physical activity is beneficial to overall cardiovascular health,” Franklin said. “It is important to start exercising—but go slow, even if you were an athlete in high school.” RELATED: If You Notice This When You’re Walking, Your Heart May Be in Trouble.