Researchers have long known that moderate exercise has a beneficial impact on the body's response to inflammation, but what's been less understood is why. New research done on a mouse model suggests that the answers may lie at the production level of macrophages—white blood cells responsible for killing off infections, healing injury and otherwise acting as first responders in the body. "Much like if you train your muscles through exercise, we showed that exercise of moderate intensity ended up training the precursors of those macrophages in the bone marrow," says Ali Abdul-Sater. "The way that exercise is doing this is...