The American Heart Association has cautioned that, “Exercise, particularly when performed by unfit individuals, can acutely increase the risk of sudden cardiac death and acute myocardial infarction in susceptible people” (Circulation, Feb 26, 2020). The authors cite more than 300 scientific articles showing that exercising excessively long and intensely may be associated with heart damage, increased plaque formation in arteries, scarring in the heart itself, markers of heart damage in the bloodstream, or irregular heartbeats called atrial fibrillation.

However, a recent review of 48 research articles found no reduction in lifespan, no matter how much a person exercises (Br J Sports Med, Aug 12, 2019). The authors said, “There was no threshold beyond which lifespan was compromised.” Exercise is associated with a 30 to 50 percent drop in deaths related to heart disease (Circ Cardiovasc Qual Outcomes, 2014;7:597-602), and with reduced need for medications to treat high blood pressure, high cholesterol, or diabetes (Med Sci Sports Exerc, 2007;39:1933-1941).

Some people do have heart attacks and die while exercising, but fewer than five percent of sudden deaths due to heart problems in men 35 to 65 occurred during sports activities (Circulation, Apr 21, 2015;131(16):1384-91). Furthermore, people who have already had a heart attack can markedly reduce their chances of having another heart attack by starting an exercise program, and those who exercise intensely are protected the most from suffering another heart attack (Mayo Clin Proc, Sept 2014;89(9):1187-94).

Who is at Risk for Suffering a Heart Attack during Exercise?
The highest number of sudden heart attack deaths occurs in highly-competitive sports in athletes under the age of 35 (Circulation, 2018;137:1561-1570), and the estimated incidence of heart attack deaths during any exercise is highest in older people, at about 21 deaths per one million participants per year (Circulation, Apr 21, 2015;131(16):1384-91). Those at highest risk for suffering a heart attack or sudden death during exercise are people over 35 who already have significant heart attack risk factors (N Engl J Med, 2012 Jan 12;366(2):130-40). Athletes who die during exercise often had warning symptoms long before they died, such as an unexplained drop in athletic performance, chest pain, shortness of breath, heart palpitations or fainting (Circulation, Apr 21, 2015;131(16):1384-91). These people possibly could have been diagnosed and saved by getting a stress exercise electrocardiogram when they started to develop symptoms of heart disease (Eur J Cardiovasc Prev Rehabil, Dec 2006;13(6):859-75).

Warning signs of increased risk for an impending heart attack (Lancet, 2011;378:1244-1253) include:
• Pain or discomfort in the chest, neck, jaw or arms, at rest or with physical exertion
• Unusual shortness of breath
• Light-headedness
• Ankle swelling
• Rapid or irregular heartbeat
• Burning or cramping sensations in the lower extremities when walking
• Heart disease indicators such as high blood pressure, blood sugar, or LDL cholesterol
• Kidney disease
• Diabetes

People who suddenly increase the length and intensity of their training are at increased risk for heart attacks during exercise. This includes people who are starting a new exercise program, or regular exercisers who decide to enter an endurance event such as a marathon or triathlon and suddenly increase the intensity and duration of their exercise programs (Circulation, Feb 26, 2020). The American Heart Association is concerned that some of the millions of people doing endurance exercises and competing in endurance sports may have pre-existing conditions such as heart arteries blocked by plaques or heart or blood vessel abnormalities. Long and intense exercise may harm them. Those who have any questions about their health or a family history of heart or blood vessel disease should check with their doctors before they start or increase their exercise programs. Remember, even well-trained endurance athletes can suffer from heart disease or structural abnormalities.

How to Start a New Exercise Program or Increase Your Intensity
When you have been checked by your doctor and are ready for your new exercise program, you should start very slowly. Gradually build up your effort until you are able to exercise for at least 30 minutes a day, five days a week. For example, if you are just starting a walking program, start walking at a comfortable pace and stop that session when you feel any local discomfort, pain or tightness in your body, particularly in your leg muscles. Try to walk every day and never try to exercise through discomfort or pain. After a few months of this background training and when you are able to exercise comfortably for 30 minutes a day at a slow pace, you can check with an experienced participant in your chosen sport to help you start more intense training. See How to Start an Exercise Program and All Exercisers Can Gain Health Benefits from Elite Training Methods

My Recommendations
I believe that with few exceptions, virtually everyone should try to exercise every day. Older athletes can and should continue to compete into their later years, but they need to remember that preventing heart problems involves more than just exercising. You can help to prevent heart attacks, cancers, dementia and premature death by following an anti-inflammatory lifestyle:
• Eat lots of fruits, vegetables, whole grains, nuts, beans and other seeds
• Avoid or severely restrict sugared drinks, sugar-added foods, red meat, processed meats and fried foods
• Lose excess weight if overweight
• Keep hydroxy vitamin D levels above 20 ng/mL (Current Atherosclerosis Reports, Jan 23, 2017)
• And of course, exercise regularly

Exercise to Help Prevent a Heart Attack
Vigorous Exercise Won’t Hurt a Healthy Heart