Regular exercise is one of the most important activities for improving heart health and maintaining a healthy brain, body, and lifestyle. However, recent research suggests that too much exercise can actually harm the heart. Several recent papers have shown that “overdosing” on exercise can have diminishing returns for heart health and can lead to a greater risk of cardiac arrest, heart rhythm issues, and heart attacks.
The American Heart Association (AHA) recently released a statement that reviewed over 300 studies to summarize the risks and benefits of intense exercise. There was a specific focus on high-intensity exercise (e.g., HIIT workouts) and high-volume endurance exercise (e.g., marathons and triathlons) because these activities have become more popular in recent years and could increase risks of certain heart issues.
Exercise has a U- or reverse J-shaped dose-response curve for certain cardiovascular problems: both too little exercise and too much exercise can be harmful. Following are some of the key takeaways about extreme exercise and heart health.
While the absolute risk is relatively small, the AHA found that sudden cardiac death (SCD) and acute heart attack risk both increase during and immediately after bouts of exercise. Interestingly, for marathon and half-marathon participants, almost 50% of SCDs occurred in the last mile. This suggests that runners should be careful about changes to their behavior, such as sprinting, as they approach the finish line.
Certain factors, especially a history of being relatively sedentary, can increase cardiovascular risk related to exercise. Even for those who are not overweight, the risk from exercise tends to be greatest if you are unaccustomed to regular exercise (e.g., new runners or people who just started an exercise regimen). Risk is also increased for participants in sudden, strenuous bursts of exercise, which put a lot of strain on the heart.
One consistent finding was that long-term endurance exercise training causes changes to the heart (including enlargement of the heart’s chambers, improved functioning, and rewiring of some electrical impulses), but these changes are not considered harmful. However, high-intensity, high-volume training may also have negative impacts, including increased risk of irregular heart rhythms (atrial fibrillation) and calcified plaque buildup on the arteries leading to the heart.
To minimize risks from extreme exercise, the AHA recommends incorporating consistent warm-up and cool-down routines for endurance athletes. Additionally, be aware of symptoms of heart issues while exercising, such as shortness of breath, chest pain, chest tightness, or lightheadedness. If you have not been working out regularly, start with shorter, low-intensity workouts, and consider talking to your doctor about your heart disease risk before beginning to exercise.
Remember, most people are far more likely to get too little exercise than to get too much, and the benefits of exercise generally far outweigh any risks. If you are concerned about your level of exercise or potential heart issues, talk to your doctor, or consider seeing a cardiologist or endurance training specialist.