ST. LOUIS — Susan Darcy had a good friend who had just turned 50 and did one. And then all her friends in her running/walking group did it.

She and her husband were running about 10 miles a week, and figured they could, too. This spring, they finished the Cincinnati Flying Pig Marathon — " just to prove to myself that I could do it," said Darcy, 51, of St. Peters, Mo.

These grueling 26.2-mile races used to be for the fittest of the fit, the seasoned athletes. But now, people of all sizes, ages and skills are taking on the challenge.

Statistics compiled by Running USA, a professional association devoted to improving the status of road racing and long-distance running, show that 25,000 people ran a marathon in 1976. Last year, nearly 425,000 went the distance.

More women running

The phenomenon includes a surge of women. Twenty-five years ago, only 10 percent of marathon finishers were women. Now, it's 40 percent.

Many take on the challenge for health benefits. But some doctors worry that some runners — especially novices and those older than 40 — are unprepared for the toll a marathon takes on the body.

Information

Team in Training: www.teamintraining.org

Oprah Winfrey was one of the first to make marathoning attractive to women. She finished a marathon in 1994 when she turned 40. No woman could say she was too busy, big or old any more.

Numbers continue to grow as training programs that raise money for charities have become popular. The largest is Team in Training, which will train almost 30,000 people to run or walk a marathon this year and raise nearly $85 million for The Leukemia and Lymphoma Society.

The programs, geared with beginners in mind, offer step-by-step training, a coach and informational clinics. Their mantra is that anyone can be prepared to run or walk a marathon in four to five months, and they promise a fun and rewarding experience. About 65 percent of Team in Training participants are women, and nearly 85 percent have never run a marathon.

Barb Cox, 32, of St. Peters, said she signed up for Team in Training in part because she couldn't get motivated to go to the gym. Mainly, she said, she wanted to help others.

"I felt I needed to give back," she said. "This was a great way to do it."

Diverse, smiling and triumphant people are portrayed at the Team in Training Web site and in its materials.

Participants must raise $3,000 to $4,000 and get airfare and accommodations paid for to run marathons in vacation destinations like Phoenix, Dublin and Hawaii. There's a pre- and post-party. And the marathons themselves are like big parties.

"It's a blast," campaign coordinator Jeff Shaw told a roomful of 16 people at a recent Team in Training recruitment meeting in St. Louis. "It's all just a lot of fun."

Serious race, serious risks

Doctors stress that running or walking a marathon is a serious endeavor that carries a high risk of overuse injury.

Dr. Scott Van Nest said he advises some — because of their body mechanics and alignment — to forego training for a marathon. He is a physical therapist at the Sports Medicine and Training Center in Webster Groves, Mo., and has worked with runners about 18 years.

Everyone, he said, should be evaluated by a doctor to forecast problems and devise a plan for tolerating the stress.

Marathon-training programs are good for camaraderie and motivation, but he warns: "You are getting a generic approach to prepare for a race. That may work for some people but not for others."

Doctors say any nagging pain is a sign a runner might be overdoing it. Rest or medical attention might be required, or both. Trying to run through the pain will result in a more serious injury that takes longer to heal. Pain also can throw off your natural gait and lead to other problems.

Susan Darcy started experiencing plantar fasciitis while training for the Flying Pig Marathon. She'd been running only a couple of years and had developed her training program from online information and talking with other runners.

Van Nest helped get her to the finish line without pain — mainly by taping her foot — and she now is using a strength and flexibility program he developed to improve her running mechanics.

Health benefits come from regular exercise that can be maintained through a lifetime, Van Nest said. Someone training for a marathon has a 40 to 60 percent chance of getting a musculoskeletal injury like a stress fracture or knee pain.

The Institute of Medicine recommends for adults an hour of cumulative exercise a day at moderate intensity — such as a brisk walk, climbing stairs, house cleaning — "to maintain cardiovascular health at a maximal level." For high-intensity exercise, such as jogging, only 20 to 30 minutes a day will do.

Mark Reinking, who teaches physical therapy at St. Louis University, agrees that longer is not necessarily better.

"What's curious to me is that there seems to be a phenomenon occurring where folks jump into running as a fitness experience and almost immediately set their sights on a marathon," said Reinking, who teaches physical therapy at St. Louis University.

But nearly everyone who has run the marathon describes an incredible feeling of pride and elation that far outweighs any pain. For some, it's been a life-changing event, bringing them to tears as they cross the line.

For others like Amber Woods, 23, of St. Louis — who hobbled to the finish line and then couldn't run for six weeks — it's the cachet.

"It's so cool to say I've done a marathon," she said.