You are more likely to be killed by your couch than by a stroke or an accident, says Dr. Vonda Wright, an orthopedic surgeon at the University of Pittsburgh Medical Center.

There are 35 diseases, collectively known as Sedentary Death Syndrome (SeDS), associated with a sedentary lifestyle, she said. Each year, about 250,000 Americans die from them. Only heart disease (650,000) and cancer (550,000) kill more.

Since only 28 percent of Americans exercise regularly, an estimated 60 percent of the population is thought to be at risk for SeDS. The term was coined by Dr. Frank Booth, a professor at the University of Missouri. SeDS will add up to $3 trillion to the nation's medical bills by the end of the decade, he predicted in 2001.

Among the ailments clustered under the SeDS umbrella are arthritis, type 2 diabetes, breast cancer, colon cancer, and osteoporosis.

Exercise can lengthen your life by more than three years, said researchers at the Erasmus Medical Center in Rotterdam in the Netherlands. For their 2005 study, the researchers analyzed four decades of data collected by the Framingham Health Study, a long-running analysis of the health of residents in that Boston suburb. They found that people who exercise moderately live, on average, a year and a half longer than people who exercise very little or not at all. People who exercise a lot live 3.5 years longer than sedentary people, the researchers said.

Exercise also vastly improves the quality of life, especially for senior citizens, said Dr. Wright, who is the director of PRIMA, a UPMC sports medicine program to help aging athletes perform their best.

PRIMA is an acronym for Performance and Research Initiative for Masters Athletes. It's the first program of its kind anywhere in the country.

Though PRIMA was established primarily to study and to serve the needs of aging, hard-core athletes such as marathon runners, long-distance cyclists and triathletes, its most popular program is designed to make athletes of baby boomers who've never exercised regularly before.

That program is START, which is designed to take you from your couch to running a 5-kilometer race in 12 weeks. Eighty-nine people took part in the inaugural START in June, which prepared novices to run in the Richard S. Caliguiri City of Pittsburgh Great Race on Sept. 30.

"It was a very, very informative, motivating program," said Karl Gustafson, 52, an order planner for Allegheny Ludlum Steel Corp.

He had the motivation to exercise, said Mr. Gustafson, who lives in Lower Burrell, but he wasn't doing it right.

"I had been trying to do the same kind of workouts as I did in high school, and I was constantly getting strains and pains," he said. "I spent 50 percent of my time healing from my workouts."

Maureen Anderson, 54, of Fox Chapel, works in the athletic department at Pitt, but wasn't particularly athletic.

"I wanted to be more active," she said. "I started exercising about a year ago and found I really liked it."

START was a great motivator, she said. "By the time I was done with the program I could run a mile in less than 10 minutes."

UPMC plans to offer START -- which consists of a medical evaluation, weekly lectures on exercise and nutrition, group exercise and assigned at-home exercise routines -- three times a year for $300.

There is no Fountain of Youth, but exercise is the next best thing to it, Dr. Wright said. If we eat right and exercise regularly, we can lead full active lives long after the sedentary are confined to nursing homes.

"It isn't until about age 75 that biology catches up with you," she said.

Dr. Wright was the research coordinator for the Senior Olympics in 2005. Research indicates the performance of senior athletes declines about 2 percent a year between the ages of 50 and 74, she said. But at age 75 upward, it plunges at a rate of 8 percent a year.

PRIMA was established because the baby boom generation is more physically active than earlier generations of seniors.

"The baby boomers are the group that has never stopped exercising," Dr. Wright said. "The boomers have been the movers and shakers in the world, and they're refusing to be 'old farts.' "

There is no growth in health club memberships in the 18-34 age group, she noted, but there's a 33 percent-a-year growth in the 54-and-up age group.

As they age, athletes must take special precautions to improve performance and to prevent injury. For $1,200, PRIMA will design a customized plan for the hard-core senior athlete. The masters program includes a physical with an orthopedic surgeon; a performance evaluation and five followup sessions; a body composition measurement; an interview with Leslie Bonci, UPMC's sports nutritionist, and an interview with Aimee Kimball, a sports mental health trainer.

Roger Oxendale, 54, president of Children's Hospital, was one of the first to sign up for the masters program. An ultramarathoner, Mr. Oxendale has found the balanced program and expert advice have improved his performance and helps him recover faster from soreness and injury sustained in the long, long races he runs.

He ran the Great Eastern Endurance Run in Charlottesville, Va., Sept. 29. That race was 50 kilometers (31 miles). He's looking forward to running in the Mountain Masochist race near Lynchburg, Va. next month.

"Before this, all I would do is run," Mr. Oxendale said. "Dr. Wright convinced me that I need the weight training and the flexibility."

For more information about PRIMA and START, visit: sportsmedicine.UPMC.com/Mastersprogram.htm, or call 412-432-3651.