I’m serious. If you’re reading this sitting down, stand up. When you’re done, go for a walk. Dance. Run. Jump. Ride a bike. Swim. Do some yoga. Do gymnastics. Play basketball. Play softball. Play tennis. Wrestle. Skate.
Do something — for at least 30 minutes a day, five days a week, if you’re an adult.
It doesn’t matter how old you are. Or how out of shape. Or, usually, whether you have other infirmities, including arthritis or cardiovascular problems.