The Centers for Disease Control and Prevention (CDC) says you're inactive if you respond "no" to this question: "During the past month, other than your regular job, did you participate in any physical activities or exercises such as running, calisthenics, golf, gardening, or walking for exercise?"

People who are really, really inactive say "No." And there are more than you might think. Around 25% of people ages 50-64, almost 27% ages 65-74, and more than 35% of those over age 75 are sedentary.

In addition to increasing problems with balance, diminishing muscle and bone strength, and increasing the risk of heart disease and diabetes, inactivity is also a risk factor for dementia.

Ten hours a day of sedentary behavior ups the risk of dementia by 8%, and 12 hours a day by 63%, according to a six-year study of around 50,000 older adults.

The good news, according to the Mayo Clinic, is that small improvements can lead to big changes in heart health, as well as cognition and other areas of your well-being.

They recommend you start out by adding 10 minutes of physical activity twice a week. You have a better chance of sticking with it than trying to do 30 minutes five days a week right off the bat.

What you want to accomplish is a gradual and permanent increase in activity until you reach at least 30 minutes most days.