Brain benefits of exercise come from the bloodstream — and they may be transferrable, mouse study finds

A small white domesticated pet mouse with red eyes running on an exercise wheel in its cage.

Exercise has big benefits for the brain, but the exact reasons why have been mysterious. Now, new studies suggest that exercised muscles release brain-boosting substances into the blood — and at least in lab animals, that boost can be transferred from one individual to another via an injection of those substances.

Previously, common explanations for why regular physical activity is good for the brain pointed to better blood flow, less stress and a stronger heart. But those ideas didn't fully explain how movement directly affected neurons.