Editor’s Note: A reader recently forwarded to me an alarming article from VeloNews about the seemingly increasing incidence of cardiac maladies (especially, atrial fibrillation) in masters endurance athletes who have pushed themselves hard for decades, in some cases, and continue to do so far past age 50. I asked Dr. Gabe Mirkin to address the issue. A few years back, Alan Bragman, D.C., author of several of our eArticles and eBooks, wrote a first-person account of his own a-fib, titled A Primer on Atrial Fibrillation. You might also be interested in reading that. – J.M.
Virtually all doctors agree that exercise helps to keep you healthy and to prolong your life. People who exercise into later life live longer than non-exercisers and are at reduced risk for high blood pressure, heart attacks, premature death, diabetes, strokes and even some cancers.
Endurance bicycle racers who participated in the Tour de France from 1947 to 2012 live an average of five years longer than their countrymen (European Heart Journal, (2013) 34 (40):3145-3150).
Fit people are less likely to suffer a particular form of irregular heartbeat called atrial fibrillation, and a regular exercise program reduces a person’s chances of developing atrial fibrillation (Circulation, April 22, 2015). More than 36,000 middle-aged women were followed for 10 years, and those who exercised regularly were far less likely to develop atrial fibrillation (Heart, May 27, 2015).
However, extreme endurance exercisers such as bicycle racers, cross country skiers and long-distance runners who compete into their 40s and beyond may be at increased risk for atrial fibrillation (American Journal of Cardiology, October 15, 2014;114(8):1229–1233).
The incidence of atrial fibrillation appears to be more common in older athletes than in the general population (J Am Coll Cardiol, 2005;46:690–6). Recent articles in the Wall Street Journal, the New York Times and other popular media have suggested that athletes who continue to do extensive fast mileage or train for extreme endurance events in later life may be doing more harm than good.
What is Atrial Fibrillation?
Each heartbeat starts when a “battery” in the upper heart (atrium) sends an electrical impulse through the upper heart to make it contract to squeeze blood toward the lower heart (ventricle). Then the electrical impulse reaches another “battery” in the lower heart to make the lower heart squeeze blood forward. Atrial fibrillation means that the upper heart quivers and does not push blood forward, while the lower heart beats independently.
Some people with atrial fibrillation have no symptoms and do not know that they have this condition until it is discovered during a routine physical examination. Symptoms may include:
- Palpitations (a feeling that the heartbeat is racing, uncomfortable, or irregular)
- Muscle weakness
- Reduced ability to exercise
- Shortness of breath
- Chest pain
These symptoms are usually harmless, but on rare occasions an irregular heartbeat can cause sudden death by stopping the heart from pushing blood through your body.
Atrial fibrillation is the most common irregular heartbeat. It occurs in 1.5 to 2 percent of the general population and risk increases with age. It affects 10 percent of 75-year-olds and 20 percent of those over 85, because aging increases the risk factors for atrial fibrillation, such as blocked arteries, high blood pressure or diabetes.
How Atrial Fibrillation Can Harm You
When a person has an upper (atrial) heart that is fluttering, a clotcan collect there and pass to the brain to cause a stroke, or to the lungs to block blood flow through the lungs. This is so dangerous that most doctors prescribe anti-clotting agents to everyone with atrial fibrillation.
I believe that athletes with atrial fibrillation are far less likely to suffer clots that cause strokes than non-athletes with atrial fibrillation, but I have not seen any studies to support my belief. Healthy athletes can have occasional irregular heartbeats that will not harm them, but at this time, doctors treat atrial fibrillation in athletes the same way they treat their other patients.
Extreme Exercise May increase Atrial Fibrillation Risk
Two studies raised the concern about extreme amounts of exercise in older athletes. In the first study, 29 elite athletes were given MRIs to look for heart muscle scarring that increases risk of atrial fibrillation. They were Olympic or national team runners and rowers who had competed throughout their lives, including some who had completed more than 100 marathons.
In the older group of 12 athletes ages 50 to 67, half showed some heart muscle scarring (J Appl Physiol, June 2011;110(6):1622-6). Those who had trained the longest and hardest had the most scarring. None of the 17 younger athletes (20-42) or the control group of 20 older non-athletes showed this heart muscle scarring.
In the second study, on rats, a 16-week program of daily one-hour treadmill running caused widening of the upper part of their hearts and scarring in the heart muscle that could increase risk for irregular heartbeats (J Am Coll Cardiol, July 2013;62(1):68-77). The scars in the upper heart remained after the rats stopped exercising.
Risk Factors for Atrial Fibrillation
There are a number of risk factors for atrial fibrillation:
- High blood pressure is the most significant risk factor for atrial fibrillation (Hypertension, 2012 Feb;59(2):198-204). Blood pressures greater than 140/90 significantly increased risk (J Am Soc Hypertens, 2015 Mar;9(3):191-6).
- Being overweight (J Am Coll Cardiol, Jul 7, 2015). A program getting people to reduce their excess body weight markedly reduced symptoms in patients who already had atrial fibrillation (JAMA, 2013;310(19):2050-206).
- An overactive thyroid
- A very low heart rate, below 50 beats per minute (Circ Arrhythm Electrophysiol, 2013, Aug;6(4):726-31).
- Abnormal coronary artery calcium score, even with no heart symptoms (Am J Cardiol, 2014 Dec 1;114(11):1707-12). This test can be ordered by any doctor.
- Lack of exercise. Exercise helps to prevent atrial fibrillation; fit men had a 23 percent lower susceptibility for atrial fibrillation (Am J Cardiol, 2012 Aug 1;110(3):425-32).
- Aging. The older you are, the more likely you are to suffer atrial fibrillation. Walking or cycling is associated with a decreased risk in older people (Heart, 2014 Jul;100(13):1037-42).
- Possibly extreme ultra-endurance exercise.
Exercise reduces the chances of a person developing atrial fibrillation. Nobody has shown that exercise in itself causes atrial fibrillation, and it is only extreme ultra-endurance exercise that some doctors believe may increase risk for atrial fibrillation.
I think that nutrition, exposure to pollutants and other lifestyle factors are also important. I do not believe that just exercising will give you adequate protection from heart disease. To protect your heart, you should follow all of the rules that apply to everyone whether you compete in ultra-endurance events, exercise moderately or just sit on a couch.
- eat lots of fruits and vegetables
- severely restrict sugar-added foods and drinks
- restrict red meat and fried foods
- avoid smoking, second-hand smoke and third-hand smoke
- restrict alcohol
- avoid being overweight
However, some doctors disagree with me. Even if you are healthy and do not have any heart problems, your doctor may recommend that you avoid strenuous workouts.
If you have atrial fibrillation or other heart problems, some doctors will even tell you to stop exercising altogether. After all, on rare occasions irregular heartbeats can kill you. If you already suffer from atrial fibrillation, or you already have blocked arteries leading to your heart, you have to depend on your doctor’s advice.
One Senior Athlete’s Exercise Program
I am 80 years old and do not have atrial fibrillation or known heart disease. I race with others 20 to 30 miles on my bike three times a week and know that I have to back off when my leg muscles start to feel stiff and heavy.
I race for the sheer pleasure of riding fast. There are no trophies or financial rewards. On my other four days, I try to do controlled 50-pedal-stroke intervals until my legs feel heavy or hurt.
For most of my life, first as a marathon runner and then as a cyclist, I had exercise-induced injuries all the time. It took me more than 70 years to learn when to go slow and when to take a day off.
Most mornings, my leg muscles feel heavy and ache from my previous day’s workout. If my legs do not feel better after riding my bike for 10 minutes, I take the day off or ride very slowly.
I do not ever plan to do slow junk miles and I do not care how few miles I put down in my diary. I usually have to take off one day a week and go slowly one day a week. I also follow all of the rules I have listed for a healthful lifestyle.
Gabe Mirkin, M.D., is a sports medicine doctor and fitness guru. A practicing physician for more than 50 years and a radio talk show host for 25 years, Dr. Mirkin has run more than 40 marathons and is now a serious tandem bike rider with his wife, Diana. His website is http://drmirkin.com/. Click to read Gabe’s full bio.