What Fit People Need to Know About 'Athlete's Heart'

There’s no doubt that exercise benefits your cardiovascular health and pretty much every other part of your body. Just like your quad or your bicep responds to training, putting your cardiac muscle under controlled stress allows it to adapt and strengthen, becoming more powerful and efficient.

But when you train hard for years, your heart undergoes more significant changes to adapt to the load, consequences experts sometimes refer to as “athlete’s heart.”

The long-term implications aren’t completely understood. Some research suggests the link between training and heart disease risk is more of a U-shaped curve than a declining slope. In other words, your odds of heart trouble decline as you go from sedentary to moderately active. But when you work your heart vigorously for hours a day, your risk may start to rise again.

“There’s a sweet spot of moderation in which we can maximize our health from a cardiovascular standpoint,” says Jared Bunch, M.D., medical director of heart rhythm services for the Intermountain Healthcare Heart Institute and a member of the American College of Cardiology Sports Council Leadership Committee.

However, the data is far from definitive, says Jeffrey Lander, M.D., associate director of Sports Cardiology at Morristown Medical Center in New Jersey. Long-term research is still needed to understand the way heart problems manifest in athletes. Changes that look harmful in the highly fit might not lead to the same outcomes as they do in the less active.

As they continue to study the issue, cardiologists concur: Merely being athletic doesn’t offer immunity to heart problems. If you have symptoms—including chest pain, shortness of breath, or a sudden and unexplained drop in your athletic ability—see a doctor.

In addition, while athlete’s heart doesn’t necessarily require treatment, it can mimic the signs of serious heart problems. So it’s good for athletes and their health care providers to know the basics.

What is athlete’s heart?

Years of endurance training—think running and cycling—place high demands on your heart’s ability to power hard-working muscles. To catch up, your body works to boost what’s called cardiac output, or the amount of blood it pumps out in liters per minute, says Justin Trivax, M.D., medical director of the Cardiovascular Performance Clinic at Beaumont Hospital in Michigan.

The main upgrade required is an enlargement of the left ventricle, which does the heavy lifting when it comes to pushing oxygen-rich blood out through the aorta to the rest of the body. The muscular walls of this chamber thicken and the space inside expands. Meanwhile, the heart’s other chambers work hard to keep up, also enlarging.

That increase in cardiac output means your heart doesn’t have to work as hard when you’re not at the gym, Dr. Trivax says. That’s why athletes often have resting heart rates that might cause alarm in anyone else.

Strength training, too, alters the heart. “Unlike endurance training, where we get a big volume challenge to the heart, with strength training it’s a big pressure challenge,” Dr. Lander says.

Lifters—especially those who bear down and hold their breath, using the Valsalva maneuver—cause temporary but significant spikes in their blood pressure. As they repeat this over time, the walls of their heart can thicken, though the left ventricle doesn’t typically enlarge as it does in endurance athletes, Dr. Lander says.

What are the consequences of athlete’s heart?

These alterations to the heart are part of what powers you to the finish line or to your new deadlift max. But they may not be completely benign. In endurance athletes, patches of scar-like tissue called fibrosis may form as the heart’s chambers stretch, potentially altering the way electrical signals travel through your heart, Dr. Bunch says.

Indeed, many (but not all) studies showmiddle-aged and older endurance athletes, especially men, have higher rates of a dangerous type of arrhythmia called atrial fibrillation. This occurs when the heart’s upper chambers quiver and beat out of sync. Atrial fibrillation can cause symptoms like weakness, shortness of breath, and a drop in athletic capacity, and contribute to the risk of conditions like stroke and heart failure, Dr. Trivax says.

These changes may take about three to four months to develop, and occur primarily in people who train more than an hour a day or 420 hours per year, Dr. Bunch says.

For reference, the latest exercise guidelines for Americans—published in November in JAMA—recommend healthy adults log either 150 minutes (2 hours and 30 minutes) to 300 minutes (5 hours) a week of moderate-intensity exercise, or75 minutes (1 hour and 15 minutes) to 150 minutes of vigorous activity, per week.

While more than five hours weekly of moderate movement may confer added health benefits, the 17 experts on the guidelines’’ drafting committee stopped short of making the same claim for additional vigorous workouts.

There’s also evidence that long-time endurance athletes have higher levels of coronary artery calcium, a hard buildup in blood vessels that can contribute to heart attacks. But what isn’t yet clear is whether calcium buildup poses the same risk in athletes as it does in the less active, Dr. Lander says.

A study published in February in JAMA Cardiology found although people who exercised a lot—the equivalent of running six miles at 10-minute pace per day—had more calcium buildup, but that didn’t correlate to an increased risk of death from heart disease. In fact, any way the researchers sliced it, the risk of dying was lower for the well-trained than the sedentary.

What should you do about athlete’s heart?

Elites and pros typically undergo heart testing, and Dr. Trivax suggests recreational athletes do the same: “Anyone who is participating in routine exercise should have some cardiovascular workup, especially if they’re pushing themselves to the extremes,” he says.

This type of screening can detect impending problems that increase your risk of a sudden heart event during physical activity. For instance, your doc might spot early warning signs of aortic dissection—a tear in the wall of the aorta that’s often fatal, and can be brought on by the pressure changes that occur with strength training.

One problem: signs of the athlete’s heart can look very similar to cardiomyopathies, diseases of the heart muscle that can either be inherited or develop due to other conditions, like high blood pressure or diabetes. Often, cardiomyopathies contribute to an athletes’ sudden death on the field or in a race, Dr. Lander says.

Telling the difference can be tricky—but more advanced procedures, such as cardiac MRIs, are giving cardiologists more tools to make the distinction, Dr. Lander says. If it’s still unclear, your doctor might have you stop training for a little while to see how your heart responds; many signs of the athlete’s heart decrease after a couple of months off, he says.

If you do have an underlying cardiomyopathy or other illness, a sports cardiologist can work with you on the safest way to approach your workouts, Dr. Trivax says.

Otherwise, athlete’s heart isn’t an illness or a condition like heart failure or high blood pressure. So, it doesn’t require treatment on its own.

What it should prompt, however, is vigilance, Dr. Trivax says. Fortunately, athletes are tuned in to their bodies—and tools like heart rate monitors (and even the Apple Watch) provide additional data.

Talk to your doc if you feel your heart racing, skipping, or jumping when it shouldn’t, or if you notice sudden and unexplained changes in your heart rate—say, a resting rate of 70 when it’s normally 50, or a spike to 180 on a sprint or climb where you normally max out at 130, Dr. Trivax says. And, make sure your doctor knows if you have a family history of heart problems.

Other red flags include passing out during exercise, chest pain, and just overall feeling like your performance is off for no apparent reason. “These are more subtle—not reaching your peak goals that you were able to reach before, or feeling like you’re really pushing harder than you used to,” Dr. Lander says. “Or even if you’re talking about a team sport, just all of a sudden feeling like you’re not able to keep up with teammates and nothing else has changed.”

If you do develop atrial fibrillation or another heart problem, treatment can sometimes prove challenging. Many cardiac drugs aren’t ideal for athletes due to side effects like dehydration, electrolyte abnormalities, poor performance, and muscle aches.

That’s another reason to see a sports-focused cardiologist, Dr. Trivax says. He or she can work to balance risks and benefits with an eye to your athletic endeavors.

How can you avoid athlete’s heart?

You can also do a lot to protect your heart outside the doctor’s office, Dr. Bunch says. The same lifestyle advice that applies broadly—eating a nutritious diet, getting enough sleep, and not smoking—also holds true for athletes.

In addition, use caution with energy drinks and supplements. Highly caffeinated energy beverages can cause dangerous heart problems—some contain more than 300 milligrams, not far off the 500 milligrams Dr. Bunch uses in the lab to induce abnormal heart rhythms. Those effects amplify with exercise.

And supplements may have hidden cardiovascular dangers—a 2018 JAMA study found unapproved ingredients in nearly 800 muscle-building, weight-loss, or sexual enhancement supplements, including anabolic steroids and sibutramine, pulled from the market in 2010 due to heart risks.

Moving up in age groups? Resist the urge to boost your performance with testosterone, Dr. Bunch advises. Too-high levels of the hormone can also thicken the wall of your heart, further increasing your risk of abnormal rhythms.

Above all, don’t let any of this scare you out of a fitness routine altogether. Those physical activity guidelines? More than three-fourths of Americans don’t even reach the minimum. Though he advocates striking a healthy balance, “we spend almost all our time telling people to please exercise,” Dr. Bunch says.

Heart risks are still the greatest in people who never leave the couch, he notes. And if you do happen to have a heart attack or other serious issue, your prognosis is generally better if you’re fit than if you’re inactive, Dr. Trivax says.

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