You know that friend of yours, the one who's really into running? He might actually be running himself right into an early grave: new research has discovered that too much exercise can be bad for your heart.

Unfortunately, while moderate exercise has been proven beneficial to maintaining a healthy human condition, researchers say that regular, intense exercise for an hour or more can stretch the heart tissue and ultimately do more harm than good to the old ticker.

Cardiologists James O’Keefe and Carl Lavie say that if you want to work out at full throttle, you should only do so for about 30-50 minutes per day. Any more than that can result in tearing and scarring, which can cause bizarre heart rhythms to develop.

In two separate studies, the doctors found that health benefits were only significantly found in those people who ran between five and 20 miles per week. Additionally, those who ran at a “comfortable jog” rather than a fast pace were healthier overall.

Cardiac professionals from the British Heart Foundation add that moderate-intensity physical activity can reduce the risk of death from heart disease by 50 percent. They recommend that every adult get at least “30 minutes a day, five times a week.”

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