SEATTLE - Today may not be "business casual" day at the office, but it is National Start Walking Day, when the American Heart Association encourages everyone to wear sneakers to work and get some exercise.

Rachel Larson, a certified personal trainer and registered dietitian, says that for those who spend most of their days on sedentary jobs, it's important to take a little time out to stretch, walk and just move around.

"Take a break. Push away from your computer, push away from your work station and walk. Maybe it's just walking through the building and back to your desk again. Maybe it's walking up and down the stairs a few times. Maybe it's walking down the hall to talk to a co-worker instead of sending an e-mail."

She also suggests having walking meetings or taking part of the lunch hour for a brisk walk. The heart association estimates people gain two hours of life expectancy for every hour of regular, vigorous exercise they do - and that's true even if they start at middle age.

For those who haven't been active for awhile, Larson suggests starting with 10 minutes of walking and adding five minutes a day until an ideal time of 30 minutes is reached.

"That helps with reducing the risk of heart disease, it helps with weight maintenance, it helps reduce stress, and it's just all-around great to be outside and getting some fresh air."

Health care administrator Michael Gibbs says walking is the ideal heart health activity; it's inexpensive and doesn't take long to to make a difference.

"The beauty of walking as a physical exercise and exertion is that, for no more than 150 minutes per week, you can reduce your risk of cardiovascular disease by 15 percent."

The heart association estimates that even walking 20 minutes a day will burn seven pounds of body fat each year. Other suggestions and resources for workplace walking campaigns are online at startwalkingnow.org.