Another reason to turn up the exercise intensity: It may keep your brain young. An observational study published online March 23, 2016 in Neurology examined 876 people, average age 71, who were enrolled in the Northern Manhattan Study. The participants were asked how long and often they exercised prior to the study. Approximately 90% reported either no exercise or light exercise, such as walking and yoga; 10% did higher intensity activities like running and aerobics.

An average of seven years later, each person was given a brain MRI and tests on memory and thinking skills. The tests were repeated five years after that.

When looking at people who had no signs of memory and thinking problems at the study's start, researchers found that those reporting low activity levels showed a greater mental decline over the five years compared with those with high activity levels. The difference was equal to 10 years of brain aging, according to the researchers. The effect also remained after researchers adjusted for other factors that could influence brain health, such as smoking, alcohol use, high blood pressure, and body mass index.