Endurance Exercise: Too Much of a Good Thing?
Does long term endurance athletic activity have negative effects on the heart?
At first glance, the question may catch some off guard. There was a time when it was thought that if you could run a marathon, you were immune from heart disease.
We now know that isn’t true, but more recently there have been concerns raised that long term endurance athletes might be at even higher risk of heart disease than those who are less active.
This is a hypothesis that has been proposed by Dr. James O’Keefe, MD, a former marathoner and cardiologist. I recently heard Dr. O’Keefe’s talk on this and it’s a great talk. I also had the pleasure to meet with him after his presentation and found him to not only be a great doctor but a great guy as well.
There is no doubt that regular physical activity has many beneficial health effects, but there seems to be diminishing returns as people exercise longer and harder. Above about an hour a day, there doesn’t seem to be much health benefit to longer exercise, but are there increased heart risks with longer exercise? The answer to that isn’t clear.
Here’s what we know.
1. Exercise is good for you. You live about 7 years longer if you exercise regularly. Few things can improve health as much as being regularly physically active and most of the benefit comes from getting off the couch and becoming moderately active.
2. The heart can undergo changes that can be confused with heart disease (chambers can become enlarged, walls can become thick, the ECG can look abnormal). This is called “athlete’s heart” and, in general, is thought to not be associated with heart disease.
3. The heart rhythm problem atrial fibrillation is 5 times more common in masters athletes than controls. This may be related to increased atrial size, scarring from many episodes of “micro-damage” from strenuous athletic events, or that athletes have slow heart rates and high vagal tone.
4. About ½ of marathon runners have an abnormal troponin level after the race. Troponin level is determined from a blood test and is most commonly used in clinically practice to determine if heart damage or a heart attack has occurred.
5. The right ventricle (that pumps blood to the lungs) is bigger and has less vigorous function after a marathon. The right ventricle returns to normal within a week.
6. Sudden death in a marathon is rare, less than 1 in 100,000. Above the age of 35 years, the most common cause of sudden death during an athletic event is artery disease.
7. There are 2 large studies (although observational and retrospective which means they aren’t scientifically the strongest) that suggest that the health benefits of exercise diminish (although don’t reverse) at higher levels (about 20 miles a week, faster than 8 minute miles, more than 45 minutes a day)
8. There are also 2 small studies that suggest a small number of master’s athletes (about 12%) have scar formation/fibrosis whereas about 4% of the normal population had fibrosis.
So far, we don’t have enough data to know if long term endurance athletes have more heart disease than those who are less active.
My advice to my master’s athletes patients is that if they exercise more than an hour a day, they are doing it for something besides health and that there MAY be some risk. Some decide to tone it down some, but most decide that the benefits of continuing to compete at a high level is more than the possible risks.
And the Beat Goes On,
R. Todd Hurst, MD, FASE, FACC