Regular exercise has long been recognized as a way to improve overall health and longevity, but a breakthrough study has us one step closer to learning exactly how. A Swedish research team has discovered that the genes you’re born with don’t necessarily limit your athletic potential and that long-term endurance training improves athleticism by changing skeletal muscle DNA.

The improvements are a function of epigenetics, the process through which our lifestyles and environments—and those of our ancestors—permanently alter how our cells interpret DNA. As it turns out, maintaining an endurance-training regimen not only improves cells currently making up our muscles but teaches them to produce improved cells, too.

Four times a week for three months, the researchers had 23 young, fit men and women engage in 45-minute sessions of one-legged cycling. After comparing biopsies from the exercised legs and unexercised legs, they realized there were areas of overlap between epigenetic markers and changed activity in 4,000 genes. Increased epigenetic methylation—or interference in the basic structure of DNA units, called nucleotides—was seen alongside increased activity in genes associated with skeletal muscle adaptation and carbohydrate metabolism, while the opposite was seen in genes associated with inflammation.

"This could be of great importance for the understanding and treatment of many common diseases such as diabetes and cardiovascular disease, but also for how to maintain a good muscle function throughout life,” principal investigator Carl Sundberg said in a press release. “Interestingly, we also saw that there were epigenetic differences between male and female skeletal muscle, which may be of importance to develop gender specific therapies in the future."

The study is slated to be published in the journal Epigenetics.