New research says too much exercise can kill you, but how much is too much?

Study Says One Hour Run Could Equal 7 Extra Hours Of Life

Physical exercise is known to help boost mood and energy and keep heart disease at bay. But overexertion can be quite dangerous and sometimes fatal, especially for white men.

That's according to a new long-term study from Mayo Clinic Proceedings, for which researchers analyzed workout and health patterns of 3,175 black and white men and women between ages 18-30.

Over the course of 25 years, the men and women participated in the Coronary Artery Risk Development in Young Adults study, self-reporting their health and exercise and coming in for eight follow-up examinations, as well as getting heart scans.

The researchers found that those who exercised more than three times the recommended amount per week were more likely to develop heart disease than those who exercised a moderate amount. And white men were specifically at risk.

For reference, the Mayo Clinic recommends at least 150 minutes of moderate aerobic activity, or 75 minutes of vigorous activity or 75 minutes of a combination of both moderate and vigorous aerobic activity each week.

Experts also recommend strength training exercises for all major muscle groups at least two times a week.

According to the new research, white men who worked out approximately eight hours per week (or more) have double the risk of suffering from heart disease than white men who exercised less than two-and-a-half hours each week.

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White men exercising at high levels are also 86 percent more likely to have plaque buildup in their heart arteries by the time they reach middle age compared with those who exercise moderately.

This could be because exercise overexertion can place significant stress on the arteries.

Regular exercise keeps your larger arteries flexible and elastic enough to allow more blood to flow when needed, which keeps your blood pressure at normal levels when your body is under stress.

But high levels of exercise, over time, can keep your cortisol up for longer periods of time, cardiologist Joel Khan told CBS News.

And according to study co-author Jamal Rana, such overexertion can lead to a higher coronary artery calcification (CAC), a clinical measure of the plaque and calcium buildup in your arteries.

While white men exercising at high levels faced a significant (86 percent) risk of plaque buildup, of all the participants who worked out more than seven-and-a-half hours per week, there was only a 27 percent increase in plaque buildup risk.

What makes white men so susceptible? Co-author of the sudy, Deepika Laddu, wants future researchers to dive in deeper on the issue.

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“Because the study results show a significantly different level of risk between black and white participants based on long-term exercise trajectories, the data provide rationale for further investigation, especially by race, into the other biological mechanisms for CAC risk in people with very high levels of physical activity,” she wrote in the study.

Today, heart disease is still the leading cause of death for both men and women in the U.S.

According to Atlanta-based Centers for Disease Control and Prevention, approximately 610,000 people die of heart disease in the United States every year, making it responsible for about 1 in every 4 deaths.

Read the full study at