Exercise has so many health benefits. We know that working out and staying physically active lowers the risk of a number of health conditions, including cardiovascular disease. In addition, exercise has a favorable impact on blood lipids and on glucose control and the risk of metabolic syndrome. No doubt about it! We need exercise, particularly cardiovascular exercise, for a healthy heart.
But, there’s another heart-related issue that’s surprisingly common. It’s called atrial fibrillation and it’s a type of irregular heart rhythm. In fact, it’s the most frequent heart rhythm abnormality diagnosed in athletes. Normally, the upper chambers of the heart called the atria, and the lower chambers, called the ventricles, contract in a synchronous way. With atrial fibrillation, the chambers of the heart get out of sync. The atria and ventricles seem to have a mind of their own and contract independently of each other. The result is an irregular heartbeat. Atrial fibrillation can be a constant rhythm disturbance, or it can be a rhythm disturbance that comes and go.
Although the irregular rhythm of atrial fibrillation isn’t life-threatening, it increases the risk of developing a potentially life-threatening complication, a blood clot. In fact, atrial fibrillation increases the odds of stroke by 5-fold. That’s why physicians sometimes recommend blood thinners for people with atrial fibrillation, also referred to as a-fib.
What causes this disorganized heart rhythm? Sometimes, atrial fibrillation is a sign of underlying heart disease, but not always. People with normal hearts can develop a-fib and the risk increases with age. Other health problems can trigger it as well. For example, an overactive thyroid, lung disease, and sleep apnea can sometimes bring on atrial fibrillation. Certain medications, including nicotine and caffeine, can do it as well. Also, the stress of an illness or surgery can trigger this irregularly, irregular heart rhythm.
Exercise and Atrial Fibrillation
Although exercise is a heart-healthy habit, some research suggests that extreme exercise increases the odds of developing atrial fibrillation. For example, some studies suggest that people who run marathons or ultramarathons are at higher risk. In fact, one study found that endurance athletes who do long-duration exercise have a 2 to 7X higher risk of developing this abnormal heart rhythm.
Before assuming that exercise is bad for the heart (quite the opposite), keep this factor to keep in mind. Atrial fibrillation is more common in men and then in women. For this reason, much of the research looking at exercise and a-fib has focused on men rather than women. Some experts believe the higher risk may be gender dependent. It’s not clear whether women who do prolonged endurance exercise have the same health risks as men. Also, this applies to extreme endurance exercise, not the workouts most people do to stay healthy.
Why would prolonged exercise increase the risk of atrial fibrillation? Some theories are that excessive endurance exercise disrupts the autonomic nervous system, the portion of the nervous system that controls heartbeat and other involuntary functions. Some research suggests that the nervous system is negatively impacted by long periods of endurance exercise. Another possibility is that too much endurance exercise causes remodeling of the heart or boosts inflammation, a factor that may damage the heart or its conduction system, the part that regulates the heartbeat.
So, it’s possible that extreme endurance exercise increases the likelihood of developing atrial fibrillation in men but less clear if the same is true in women. But, what if you exercise in moderation? A study published in the journal Circulation found that moderate exercise modestly lowers the risk of atrial fibrillation. It makes sense since exercise helps reduce some of the risk factors for atrial fibrillation such as elevated blood pressure. It also helps with blood sugar control and helps keep body weight in check. Diabetes and obesity place people at greater risk of atrial fibrillation and other heart-related problems as well. In fact, being sedentary increases the risk of a-fib in both men and women. This suggests there’s a sweet spot for exercise. Not getting enough of it raises your risk, but regularly running marathons or doing long periods of intense exercise on a regular basis may be detrimental.
Other Factors That May Contribute to Atrial Fibrillation in Athletes
Certainly, intense exercise isn’t the only factor that boosts the odds of developing atrial fibrillation. Some studies suggest that sports supplements, particularly anabolic steroids, may increase the risk but this is inconclusive. However, there have been cases of atrial fibrillation developing in athletes who consume energy drinks and beverages that contain large amounts of caffeine. However, researchers believe high doses of caffeine can be a trigger but is unlikely to cause a-fib unless a person is already genetically susceptible or has some other risk factor.
Keep in mind, the amount of caffeine in energy drinks can be quite high, up to 500 milligrams in one can. Some people are slow metabolizers of caffeine and caffeine stays in their system longer. This increases the risk of heart-related side effects. Another potential factor is electrolyte abnormalities. Longer periods of exercise can lead to a significant loss of electrolytes through sweat. Experts believe that this can trigger atrial fibrillation in some people.
What about Exercising if You Already Have Atrial Fibrillation?
People who have atrial fibrillation don’t necessarily have to put away their exercise shoes. A study published in the journal Circulation showed that moderate quantities of exercise are beneficial for people with this heart rhythm irregularity. In the study, participants did high-intensity aerobic interval training for 12 weeks. A control group with a-fib did no exercise. At the end of 12 weeks, the group who exercised had fewer symptoms and experienced improvements in markers of heart health, including improved cardiac function and a better quality of life.
If you have atrial fibrillation, always take the advice of your cardiologist, but it’s unlikely that they’ll tell you not to exercise at all. More likely, they’ll want to get your atrial fibrillation under control first, possibly with medications. Atrial fibrillation can cause a rapid, irregular heartbeat and you might experience dizziness or lightheadedness when you exercise until the rate is controlled with therapy. Physicians sometimes recommend a stress test before a patient with a-fib starts back exercising to see how the heart responds to exercise. They may also recommend cardiac rehab where you exercise in a controlled setting at first.
References:
· Circulation. 2016 Feb 2;133(5):457-9. doi: 10.1161/CIRCULATIONAHA.115.020800. Epub 2016 Jan 5.
· American College of Cardiology. “Is Endurance Exercise Safe in AFib?”
· Journal of the American College of Cardiology. Volume 62, Issue 1, July 2013. DOI: 10.1016/j.jacc.2013.02.070.
· J Atr Fibrillation. 2015 Dec; 8(4): 1309.