Heart disease is the number one killer in the United States, according to the American Heart Association.
Staying healthy can improve your heart health, but doctors have discovered that too much exercise can actually lead to heart disease, even death.
Their findings, however, applied to one specific group of people: white men.
Led by researchers at the University of Illinois at Chicago and Kaiser Permanente, the study found that white men who exercise at high levels are 86 percent more likely to experience plaque buildup in the heart, compared to those who exercise at low levels.
Study participants were categorized into three distinct groups based on physical activity patterns: those exercising below national guidelines, those meeting national guidelines and those exercising three-times above national guidelines.
National guidelines suggest 150 minutes of moderate exercise each week.
The studied measures the accumulation of calcium and plaque in the arteries of the heart.
The presence and amount of coronary artery calcification is a significant warning sign to doctors that a patient may be at risk for developing heart disease and a signal to consider early preventive care.
Researchers don't know why very active white men were twice as likely to suffer from heart disease than people who worked out a moderate amount.
They didn't find similar results in black men or white women.
"There might be some biological difference in the sex and race that have yet to be determined," said Dr. Danny Le, an interventional cardiologist at Medical City Arlington.
Le reviewed the study but wasn't part of the research team.
He said more study is needed, but exercise is important and the study's findings do not mean people should stop working out.
"Multiple studies have determined that people who are more active and exercise live longer," Le said.
While no amount of plaque build up is great, scientists say the kind of plaque they found may not have been the kind that easily breaks apart and causes a heart attack.