Exercised: Why Something We Never Evolved to Do Is Healthy and Rewarding

by Daniel E. Lieberman

Hypertension is a silent condition that relentlessly strains the heart, arteries, and various organs. At least 100,000 times a day, the heart forces about five liters of blood through thousands of miles of arteries that resist each squeeze, generating pressure. When we exercise, blood pressure rises temporarily, causing the heart’s muscular chambers to adapt, mostly by becoming stronger, larger, and more elastic so it can pump more blood with each stroke.30 Just as important, arteries also adapt to exercise to keep blood pressure low, primarily by expanding, multiplying, and staying elastic.31 However, when blood pressure is chronically high, the heart defends itself by developing thicker muscular walls. These thicker walls stiffen and fill with scar tissue, and eventually the heart weakens. A vicious cycle then ensues. As the heart’s ability to pump blood declines, it becomes harder to exercise and thus control high blood pressure. Blood pressure may rise as the heart progressively weakens until the failing heart cannot support or sustain a normal blood pressure. Death usually ensues.