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

by Daniel E. Lieberman

to the places they are most needed, including the vulnerable mucus-covered linings of the respiratory tract and gut.61 Further, some of the most highly redeployed cells are those most effective at fighting viruses (these include natural killer cells and cytotoxic T cells).62 Studies that compare sedentary and active people