The more intensely you exercise, the less likely you are to suffer a heart attack, even though heart attacks can be caused by intense exercise in some people who already have irregular heartbeats or blocked arteries leading to their hearts.

• Researchers had 4582 men and women, average age 46, wear mechanical accelerometers to measure their intensity of exercise. After ten years, they found that the more they moved about and the less time they sat without moving around, the less likely they were to develop heart disease and the higher their blood levels of the good HDL cholesterol (Preventive Medicine, published online May 02, 2019). Also, the women who were even moderately active had lower total cholesterols.

• The HUNT study from Norway followed 26,163 healthy men and women, average age 55.7, for an average of 13 years and found that the more fit they were, the less likely they were to develop a first heart attack (Journal of the American Heart Association, April 19, 2019). They found that a high level of fitness was even more protective in the women than in the men.

• The SUN study from Spain followed 18,737 men and women, average age 38, for six years. The researchers found lower rates of heart attacks in those who exercised intensely as opposed to those who exercised at low intensity (American J of Cardiology, Dec 1, 2018;122(11):1871–1878). They used intensity of exercise per time spent exercising to show that those who exercise intensely had half the heart attack rate, compared to those who did the same amount of exercise less intensely.

Exercise to Prevent a Heart Attack
The association between a regular exercise program and improved health is unquestioned (J Clin Prev Cardiol, 2017;6:109-14; Am J Lifestyle Med, July 1, 2009;3(1 Suppl):44S–49S), and a healthful diet in addition to exercise helps even more to help prevent heart attacks and many other diseases (Eur J Prev Cardiol, Jul 2018 ;25(11):1186-1197).

Intensity makes all muscles stronger including your heart muscle. All people lose heart muscle as they age, which increases risk for frailty and heart failure. Strengthening your heart muscle helps you to live a more vigorous lifestyle and to protect you from heart failure. Intense exercise stabilizes plaques in arteries and widens heart arteries to help protect you from a heart attack. Men with the highest ability to take in and use oxygen (VO2max) have the least high blood pressure, high HBA1C (a test for diabetes), high fasting blood sugar levels, obesity, coronary calcium scoring, abnormal treadmill exercise test, and calculated 10-year risk for heart attacks (American J of Cardiology, March 2012;109(6):839-843).

Preventing heart attacks involves both exercising and eating healthfully. Since exercise helps to stabilize plaques to help keep them from breaking off from arteries, exercise should be part of any heart-attack-prevention program. Dedicated exercisers who need to eat large amounts of food to meet their caloric needs should choose healthful, anti-inflammatory foods to avoid forming more plaques in their arteries. Check with your doctor if you have evidence of heart disease caused by a faulty diet: high blood pressure, high blood cholesterol, high triglycerides, high blood sugar, high CRP (c-reactive protein, a measure of inflammation), an abnormal EKG, or chest pain, particularly with exercise.

Can Intense Exercise Be Harmful?
Exercisers live longer and have far less heart damage than non-exercisers. However, elite athletes may be at increased risk for irregular heartbeats, increased arterial plaque size or thickened heart valves.

• Even though master athletes may be at increased risk for irregular heartbeats (atrial fibrillation), they can still benefit from continuing to exercise. Compared to non-exercisers with atrial fibrillation, they appear to be at reduced risk for suffering from serious side effects such as clots. See Irregular Heartbeats in Senior Athletes and Exercisers.

• Elite athletes may be at increased risk for larger plaques in their arteries than non-exercisers, but narrowing of arteries by plaques does not cause a heart attack. Heart attacks are caused by plaques breaking off from arteries, and exercise helps to prevent heart attacks by making plaques more stable and less likely to break off. See Exercisers Have More Stable Plaques.

• Vigorous exercisers may be at increased risk for thickened heart valves, but compared to non-exercisers, athletes with thickened heart valves still have stronger heart muscles so that they are less likely to suffer heart failure. See Exercise to Prevent a Heart Attack

My Recommendations
I think everyone should have a regular exercise program, and it is never too late to start. See How to Start an Exercise Program.
• Before you try to increase the intensity of your exercise program, you should have exercised regularly for many months, be in good shape and not have any health conditions that can harm you. Because intense exercise can cause heart attacks in susceptible people, you may want to check with your doctor before increasing the intensity of your workouts.
• Try to set up your exercise program so that you increase the pace enough on an intense day to feel mild muscle soreness on the next day. Then take easy workouts for as many days as it takes for the soreness to go away. Only then should you take your next hard workout.
• When you are training properly, your muscles can feel sore every morning. If they don’t feel better after a 10 minute warm-up, take the day off.
• If you feel pain in one spot that does not go away after you slow down, stop that workout immediately for that day. Otherwise you are likely to be headed for an injury.

CAUTION: Intense exercise can cause a heart attack in a person who has blocked arteries or heart damage. Check with your doctor before you start a new exercise program or increase the intensity of your existing program.

Checked 3/1/23