Regular exercise builds muscle and burns fat, helping get your body ready for anything. New research from Princeton University has found that it also does some remodeling in the brain that helps it handle stress with aplomb. In the study, mice that ran regularly responded to a stressor by shutting off activity in a region of the brain related to anxiety. Sedentary mice, on the other hand, showed a surge in neuron excitement. Scientists already knew that working out relieves stress—now we have a picture of how consistent physical activity may reprogram your brain to prepare it for stressful surprises.