Want to live longer? The American Heart Association says that if you take a few simple steps each day, you can pretty much guarantee it.

Each hour of exercise you get adds two hours to your life expectancy, said Drs. H.D. Sesso, R.S. Paffenbarger and I-M. Lee Jr. in the Harvard Alumni Health Study in 1995.

Brisk walking for just 15 to 20 minutes a day is enough to measurably reduce your risk of getting heart disease, high blood pressure, certain cancers, Type 2 diabetes, arthritis and osteoporosis, says the Harvard School of Public Health.

Walking is the best form of exercise for people who haven't been exercising regularly, because it's easy to do, requires no special equipment, can be done almost anywhere, and has the lowest dropout rate for any physical activity, according to the American Heart Association.

The association is working with employers throughout the country to deprive you of one of your excuses for not exercising: that you haven't got time.

It's encouraging employers to promote walking programs, and to permit employees to wear athletic shoes to work one day a week on designated "sneaker days."

The Heart Association plans to formally kick off its campaign with a National Start! Walking at Work Day on Wednesday, April 25.

Participating employers are being asked to permit their employees to wear athletic shoes to work that day, and at 2:41 p.m., to permit their employees to go outside for a brisk walk around the premises.

"We picked 2:41 to symbolize the benefits of exercise -- two more hours of life for each hour of exercise, two for one," said Karen Colbert, director of communications for the Pittsburgh affiliate of the American Heart Association.

PPG Industries Inc. is one of the more enthusiastic corporate backers of the American Heart Association's campaign.

"Our couches are killing us," said Dr. Alberto Colombi, PPG's global medical director. "There is an epidemic of problems due to our sedentary life. Any effort that entices ourselves to move our bodies through space is a good thing."

PPG plans a month of activities culminating April 25 when fitness guru Leslie Sansone will lead PPG employees on a 3-mile walk in PPG's Wintergarden, starting at noon.

"We're opening it up for anyone who wants to come," said Nancy McMahon, Dr. Colombi's chief nurse.

Ms. Sansone, nationally known for creation of her In-Home Walking Program, is the owner of Studio Fitness in New Castle.

PPG's health awareness programs begin today with a screening for cholesterol for its employees.

On the April 12, former KDKA news anchor Jennifer Antkowiak, who now is director of marketing for Ms. Sansone, will lecture on heart disease in women. On April 18, PPG employees will be screened for the warning signs for stroke.

Among other area firms planning activities for Start! Walking at Work Day are Automated Health Systems, Bayer, Chatham college, the Pittsburgh Brewing Company, Siemens, UPMC, Emerson Process Controls, K&L Gates, Vocollect and the local affiliates of Pepsi, Fed-Ex Ground, and Verizon Wireless, Ms. Colbert said.