Run For Your Health

A heart study shows that the type of exercise you do can change the structure of your body’s lifeline — for better or for worse.

Last updated: January 26, 2021
Strengthen Your Heart & Run for a Lifetime

The human heart is one seriously impressive organ. A perfectly calibrated pump that circulates blood and oxygen throughout the body, the heart more or less knows what to do before it’s even fully formed. And one of the best insurance policies you have against yours going off-script is something you were born to do.

Just like your brain is wired to learn and grow, your heart is primed to adapt to movement, especially the endurance kind, according to a recent study published in the journal PNAS. In it, researchers compared the hearts of chimpanzees with those of sedentary people, Native American subsistence farmers, long-distance runners, and football linemen.

What the team discovered: Only in humans, the left ventricle of the heart—the chamber that pumps blood to the rest of the body—is thinner and elongated, which makes it easier for the heart muscle to expand. A larger left ventricle, which they found in the group of distance runners, and to a lesser extent, in the subsistence farmers (who do a lot of walking), allows the heart to be more efficient, pumping more blood with each beat. That means your ticker has an easier go of it, which can make your workouts, as well as everyday tasks, feel less taxing.

Those who don’t engage in regular endurance activity, on the other hand, experience a very different development: a pressured-adapted heart—as in, the organ actually changes structure to move blood against constricted vessels, says study coauthor Daniel Lieberman, PhD, a professor of human evolutionary biology at Harvard. This can cause its walls to become thicker and stiffer, so your heart has to work harder to do its job. That was the case for the football linemen, who favor strength training over distance runs, and the apes, who haven’t evolved for sustained movement like humans have. It was also the case for the sedentary people, who could be headed for developing high blood pressure.

Those who don’t engage in regular endurance activity, on the other hand, experience a very different development: a pressured-adapted heart—as in, the organ actually changes structure to move blood against constricted vessels.

Daniel Lieberman, PhD, Professor of Human Evolutionary Biology at Harvard

Ready for a Remodel?

The good news is, you can build a stronger heart starting right now—even if yours has already rejiggered based on how you have (or haven’t) been moving. Within four to six weeks of regular endurance training (that’s 150 minutes a week, per the American College of Sports Medicine’s rec), you can start to see cardiovascular changes, like easier runs or step-climbing, courtesy of that expanding left ventricle. All those miles you log also increase the number of tiny blood vessels and energy-making cells in the heart, which allow the arteries there to capture more oxygen, says Barry Franklin, PhD, the director of preventive cardiology and cardiac rehabilitation at Beaumont Health in Royal Oak, Michigan.

To see the improvement in action, take note of your resting heart rate on your activity tracker. A lower heart rate at rest, a byproduct of endurance work, gives your heart more time to fill with blood. Not only will you be able to push yourself even further during aerobic sports and workouts, but you’ll also boost your long-term health: Every 10 beats-per-minute (bpm) reduction in resting heart rate improves your fitness enough to reduce your risk of heart disease and all-cause mortality by 15 to 20 percent, Franklin says. The healthiest athletes have a resting heart rate around 40 to 65 bpm, says Franklin, though the American Heart Association says anything between 60 to 100 is normal.

Of course, weight training definitely has a role in a well-rounded workout regimen. It can build muscle strength and endurance, improve insulin sensitivity, and increase lean body mass and your metabolism, says Franklin. “But we may pay a price if that’s all we do,” adds Lieberman. You don’t need to become a marathon runner. But who wants to be a chimp?

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