We’ve all been told that the more we exercise, the better off we’ll be. Especially our hearts.

But what if it isn’t always true? What if, for some people, extreme exercise actually might lead to heart problems?

Researchers are now delving into this question. For insight, we recently spoke to Neel Chokshi, medical director of the Penn Sports Cardiology and Fitness Program and cardiologist for the Philadelphia Eagles.

Is there such a thing as too much exercise?

Most people benefit from increasing activity. However, there is a small group of people for whom there has been a suggestion of negative impacts on the heart from excessive exercise. It’s early data, but there are some conditions that we are increasingly seeing with extreme exercise. They include arrhythmia and specifically, an irregular heart rhythm known as atrial fibrillation. There’s a suggestion of increased atherosclerosis. And there’s also the possibility of fibrosis, or scarring, of the heart.

Neel Chokshi is medical director of the Penn Sports Cardiology and Fitness Program and cardiologist for the Philadelphia Eagles.

How much exercise it takes to trigger those conditions is still being understood. But it’s probably a mixture of some sort of genetic predisposition coupled with a high volume of activity. There are lots of theories for why this would be. Essentially, there is some remodeling that happens in the heart from high volumes of exercise, and the changes depend on the type of activity or exercise that you’re performing.

For example, atrial fibrillation can occur in people who have been running marathons or long distances for many years, or over the course of their lives. We’ve tried to quantify this specifically, but generally it’s someone who does high-intensity exercise of five hours or more a week and has done so for at least 10 years.

Examples of high-volume endurance exercise include running and cycling long distances, or cross-country skiing.

In the case of these endurance athletes, we see high volumes of blood pumping through their hearts to accommodate the high oxygen demands during training. This can lead to enlargement of all chambers of the heart, in particular the left atrium. These individuals also tend to have slower heart rates due to their high fitness levels. We think these factors contribute to the cause of atrial fibrillation.

Recent research also has shown that people with high volumes of endurance activity may have higher amounts of coronary calcification. But the presence of arterial plaque in someone who exercises regularly does not pose the same degree of risk as it does in the general population.

High amounts of resistance activities — weight-lifting, rock-climbing, wrestling — lead to transient but significant increases in blood pressure during workouts. Over time, the heart muscle can hypertrophy or thicken as a normal and benign response to training. If you have an underlying heart condition, such as an enlarged aorta, resistance training could have implications on progression.

I would emphasize that the risk of adverse events from exercise is very low and does not apply to most people. In almost all scenarios, the benefits of exercise outweigh the risks of training.

Once changes to the heart are discovered, what’s next?

In the general population, we have a common means of treating things like irregular heart rhythms, with well-established algorithms. How to treat this in athletes is more complex and an ongoing area of research.

We don’t want people to stop exercising, but if we think the volume or intensity of exercise is contributing to their abnormality, one approach would be to back off the exercise with the idea being that these triggers would regress and lower the occurrence of these events. It’s called de-training. We sometimes use this strategy when we are not certain if the changes we are seeing in the heart are pathological in nature or physiologic.

In the scenario of an enlarged heart, we try to distinguish whether the changes are due to endurance exercise versus a disease state known as cardiomyopathy. We might ask the individual to take a break from exercise for six to 12 weeks and look at the heart again to see if those changes have regressed.

How much exercise should people be getting?

The goal for most adults is at least 150 minutes of moderate-intensity or 75 minutes of high-intensity exercise per week. Any activity or exercise counts toward that goal. And you can achieve it any way you want. It can be 30 minutes a day for five days, or 50 minutes a day for three days. Ten minutes today, and 50 minutes tomorrow.

Moderate intensity is different for each individual. It depends on your baseline level of fitness. And there are different ways of measuring it. Some simple ways are: On a scale of 1 to 10, if 10 is your maximum level of exertion, five to seven is moderate. Or, if you’re walking, walk at a pace so that if you were having a conversation with someone, you’d feel somewhat short of breath.

A lot of people track their heart rates. In that case, moderate activity is defined as 60 to 70 percent of your maximally predicted heart rate. A lot of factors go into that, but as a rule of thumb, we say that 220 minus your age is a rough estimate of your maximum rate.

Additionally, we recommend two sessions, 20 minutes per week of some sort of resistance training.

These recommendations are based on the Department of Health and Human Services activity guidelines. The American Heart Association advocates for similar goals.

You’ve studied fitness tracking devices. How can they help?

Activity trackers and heart rate monitors can be useful tools to help you understand if you’re meeting your exercise goals. The general recommendation has been 10,000 steps per day. As an initial goal for someone that does not routinely exercise, I will ask to start by targeting at least 6,000 to 8,000 steps per day. Research has shown that individuals who achieve these step goals are in the range of achieving 30 minutes of moderate-intensity activity per day. The step-tracking metric can also serve as a gauge to see what you’ve done each day. Maybe you were stuck at your desk all day and your activity levels were low. You might supplement that day by saying, “I’ll go for a walk.”

From there, I’ll ask my patients to work toward sustained bouts of 30- to 45-minute sessions of whatever they enjoy doing. Then, when they hit those goals, I’ll say to add on two sessions of resistance training per week. Typically, this would mean lifting weights or using elastic bands or engaging in other calisthenic activities, such as push-ups or sit-ups.

From a research standpoint, we’ve coupled wearables with behavioral incentives to motivate individuals to increase their activity. In one study involving people who have had a heart attack or a stent placed, we showed that financial rewards can help incentivize people. There’s ongoing work in other areas with different motivational tactics, such as support groups or creating games around the wearable.

What else should people know or do?

People often use weight loss as a metric for success. What I tell my patients is that it’s important to know that even if they don’t lose weight, all activity is beneficial for the heart. I also emphasize that you should find something you enjoy doing and can incorporate into your life. That’s important. If it’s something you enjoy, you’re more likely to stick with it, and you’re more likely to benefit from it.

Everything counts.