Moderate exercise a few days a week is good for your health, but new research shows that more may not always be better.

At the risk of encouraging you to binge-watch on the couch a little longer, too much exercise may be bad for your heart, say researchers in a new study.

But before you get too comfy, keep in mind that an inactive lifestyle increases your risk of obesity, heart disease, type 2 diabetes, and a host of other chronic illnesses.

We know this because scientists have been studying the lower boundaries of exercise for many years.

All to answer the question: What’s the minimum amount of physical activity that you need each week to live a longer and healthier life?

Recently, more studies have started to look at the other end of the exercise spectrum to see if more is always better.

One of these studies was published October 16 in Mayo Clinic Proceedings.

Researchers found that people who exercised well over the national physical activity guidelines for many years were more likely to develop coronary artery calcification (CAC) by middle age.

CAC, which is measured using CT scans, indicates that calcium-containing plaques are present in the arteries of the heart — a predictor of heart disease.

The study included almost 3,200 people. Researchers followed them for 25 years, starting when they were young adults.

At the beginning of the study, and during three to eight follow-up visits, participants reported how often and the types of physical activities they participated in.

Researchers used this information to divide participants into three groups: those who met the physical activity guidelines, those who fell below, and those who exceeded it by at least three times.

The U.S. Department of Health and Human Services’ “2008 Physical Activity Guidelines for Americans” recommend that adults do at least 150 minutes a week of moderate-intensity, or 75 minutes a week of vigorous-intensity, aerobic activity.

Vigorous-intensity activities include running, biking, swimming, exercise or dance classes, and strenuous sports.

Moderate-intensity activities include walking, hiking, golfing, home exercises, and gardening.

People who exercised three times the recommended amount — or the equivalent of 450 minutes a week of moderate activity — had a 27 percent higher risk of developing CAC during the study period, compared to those who exercised the least.

The effects of extreme exercise were even greater for white participants.

This group had an 80 percent higher risk of developing CAC. The risk was slightly higher for white men than white women.

Statistically, though, the results based on race and gender were only significant for white men. This is probably because the other groups had too few participants.

The study also reinforced the benefits of regularly meeting the physical activity guidelines.

People who exercised less than the recommended amounts were more likely to have high blood pressure and type 2 diabetes in middle age.

Does this mean the presence of CAC in people who exercise at least 7.5 hours a week is a sign of heart disease later on?

The answer is… possibly.

“High levels of exercise over time may cause stress on the arteries leading to higher CAC,” Dr. Jamal Rana, a study author, said in a press release. “However, this plaque buildup may well be of the more stable kind, and thus less likely to rupture and causes heart attack, which was not evaluated in this study.”

Rana said that they plan to continue following the participants to see how many have heart attacks, other health problems, or die early.

Other studies have found similar drawbacks to high doses of physical activity.

In the Copenhagen City Heart Study, moderate joggers had a threefold increased risk of dying early, compared to light joggers. For strenuous joggers, the risk was nine times higher.

The Million Women Study found that women who did strenuous activity daily had a higher risk of heart disease, stroke, or a blood clot breaking free in the blood, compared to moderate exercisers.

However, not all research points to extreme exercise being bad for your health.

In a Swedish study of almost 74,000 non-elite long-distance cross-country skiers, those who had finished more races had a lower risk of dying early.

Other studies have found that the arteries of male ultradistance runners have larger diameters and are able to widen more, compared to those of physically inactive men.

The authors of the current study wrote that although extreme exercisers may have higher amounts of CAC, wider arteries mean that this “may not necessarily translate into adverse clinical outcomes.”

None of this, of course, is reason to stop being active. In fact, many Americans could probably use a little more physical activity in their life.

According to the Centers for Disease Control and Prevention (CDC), slightly more than half of U.S. adults met the guidelines for aerobic activity. And only one-fifth met the guidelines for both aerobic and strengthening activities.

The current study, like other research, suggests that there may be an upper limit to the benefits of exercise. After that point, the added stress may negatively impact your body — especially the heart.

For those devoted exercisers who love to push themselves beyond these limits, this study is even more reason to put extra effort into taking care of your heart.

This includes eating a healthy diet, giving up smoking, and learning to manage your stress with practices like yoga, meditation, and mindfulness training.