We know that exercise is good for heart health. But how?

Now new research from a team based at Massachusetts General Hospital, the Harvard Department of Stem Cell and Regenerative Biology (HSCRB), Harvard Medical School (HMS), and the Harvard Stem Cell Institute (HSCI) has released preliminary findings showing that exercise can increase the generation of new heart cells, which might be crucial to maintaining heart function as we age.

Their findings not only uncover a cellular level link between exercise and healthy hearts, but also provide more reason to incorporate physical activity into our everyday routines.

Here are five things to know about this new research:

1. “Maintaining a healthy heart requires balancing the loss of heart muscle cells due to injury or aging with the regeneration or birth of new heart muscle cells,” said Anthony Rosenzweig, MD, co-senior author of the study and chief of the cardiology division at Mass General, in a recent press release. However, maintaining this balance isn’t easy — young adults can only renew around one percent of their heart muscle cells each year, and that rate decreases with age. In addition, individuals who lose too many heart cells without generating new replacements have a higher risk of heart failure.
   
2. Recognizing a need to enhance regenerative capacity of heart muscle cells, the team sought to test the effects of exercise in increasing cell formation. The team used a chemical tracer in mice to track the growth of new heart muscle cells over time.
   
3. Researchers gave groups of healthy mice and mice that had recently experienced a heart attack either access to a running wheel or no such gym privileges. The healthy mice voluntarily ran about 3 miles each day, and, most notably, they generated 4.6 times the number of new heart muscle cells compared to healthy sedentary mice. Similarly, they found that mice who had experienced heart attacks and were given running wheel access also voluntarily ran each day and showed a ~6.75-fold increase in new heart muscle cells in an area of the heart further from where the heart attack occurred.
   
4. Based on these results, the team concluded that exercise successfully stimulates the generation of heart muscle cells in mice. These findings may also have applications in the human heart and in the quest to improve the heart’s ability to create heart cells, even as we age. “Our study shows that you might be able to make your heart younger by exercising more every day,” said Richard Lee, MD, co-senior author of the study from the HSCI and Harvard Medical School, in a recent press release.
   
5. The team’s next step is to pinpoint which biological mechanisms link exercise with increased regenerative activity in the heart with the goal to better understand how these mechanisms could be applied to patient care.

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