Is too much cardio bad for you? Study says probably not
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Some research has shown that ultra-fit athletes such as marathon runners can have cardiac damage such as heart scarring or arrhythmia, raising the question of whether too much aerobic exercise can be a bad thing.

But a recent study by Colorado State University found that while some ultra-athletes showed some minor calcium buildup in their coronary arteries, they were still healthier overall than a control group of people who only got moderate exercise.

The ultra-athletes were healthy individuals between the ages of 40 and 65 who had been training and competing for at least 10 years in events like ultra-marathons and triathlons. The control group consisted of healthy subjects in the same age group who were getting at least 150 minutes of exercise per week. Both groups underwent a rigorous screening process to ensure that none of them had other health factors that might affect the results, such as obesity, high cholesterol or hypertension.

Researchers conducted a battery of vascular tests on the subjects in the lab, having them do an aerobic fitness test and assessing elements such as the stiffness of their carotid arteries and the dilation of vessels in their arms, for instance. Then the subjects were sent for echocardiograms of their heart structure/function as well as imaging of their coronary artery calcium levels. (Calcium deposits are a hardened plaque that can be a marker for cardiovascular problems, even when a person has no symptoms.) The participants also underwent cardiac fibrosis tests.

Even though a higher percentage of the ultra-athletes had calcium deposits, their overall cardiovascular health was still better than those in the control group, leading the team to conclude that extreme amounts of cardio are not deleterious to one's health.

When other risk factors such as blood pressure, cholesterol and age were used along with the calcium score to determine heart disease risk, most of the athletes were below the threshold for statin treatment.

The researchers plugged all of their data into a risk calculator for coronary heart disease and found that the ultra-athletes were not at higher risk than the control group.

"We didn't find evidence that would make us recommend that people not exercise too much," researcher said. "The overall benefits of exercise outweigh anything we saw."

The researchers added, however, that some people may have other health factors, such as a family history of heart disease, that they should discuss with their doctor before becoming ultra-athletes.