STUDY FINDS - For decades, scientists have assumed that being highly active comes at a price. Push a body harder, burn more energy, and something else must suffer, whether that’s the immune system, reproduction, or lifespan. It’s a tidy idea rooted in basic biology: resources are finite, so spending more on one thing means spending less on another. A new study put that assumption to a serious test, and the results didn’t go as expected.
Researchers at the University of California, Riverside studied mice selectively bred for more than 97 generations to be extreme runners, publishing their results in the journal Behavior Genetics. These ‘High Runner’ mice voluntarily run roughly three times farther than ordinary mice when given access to a running wheel, and stay more physically restless even without one. If the conventional wisdom about activity and biological trade-offs held up, these mice should have had fewer offspring or shorter lives than their normal counterparts. That’s not what happened.