Here’s good motivation to get up and move more: a new study published in the journal Neurology found that people who weren’t as physically active in midlife had smaller brains than their peers 20 years later. The brain scans revealed that people with a lower exercise capacity—defined as the amount of time people could exercise on the treadmill before their heart rate hit a certain threshold—in midlife were more likely to have smaller brains years later, compared with people who had high fitness levels in middle age.