Three years ago, when Tyrone Duncan was jobless, recovering from a spinal injury and a stint in a homeless shelter, some volunteers at his transitional housing site encouraged him to run with them as they trained for a race.

“I didn’t manage more than a block at a time back then, but I kept at it and they kept at it with me,” Duncan recalls.

Now Duncan, 53, is the fastest member of that running group, and he credits the regimen of training for helping him stay off drugs and alcohol. He also has a full-time job at a Giant grocery store, a position he says he got not only because of his newfound discipline but also because members of that same group helped him write a resume and learn the skills necessary for his work.

So it’s no surprise when Duncan says running turned his life around. He is far from the only person in sneakers to make that claim. A growing number of national organizations are using the sport to help kids and adults facing such challenges as homelessness, drugs and cancer. They have a variety of names — Back on My Feet, Achilles International, Alex’s Lemonade Stand, Run to Recover — but all have turned to running for the psychological and physiological benefits that training for a race can bring.

Any exercise, when done with enough vigor and for long enough, helps reduce stress and fuels the brain with chemicals that create a sense of well-being even after the sweating is done, says Michael Lehman, a researcher at the Laboratory of Cellular and Molecular Research at the National Institutes of Health. But few activities are as inexpensive and easy to do as running.

The link between exercise and better mental health has been well documented. A 2007 study of people with major depression in the journal Psychosomatic Medicine, for example, found that the effects of exercise were comparable to those of antidepressants. When the researchers followed up with the study participants a year later, they found that keeping up with exercise helped prevent relapses. And a 2008 study found that people with anxiety saw their condition ease after a two-week exercise regimen more than a control group that was not enrolled in the workout program.

Antonia Baum, a Chevy Chase psychiatrist and competitive runner who incorporates exercise into therapy sessions for some of her patients, says running seems to help people with many different kinds of issues. “A good run creates its own level of mastery; add to that the necessary imposition of structure and discipline, as well as being outdoors, which we know brings us pleasure,” Baum says.

Anne M. Mahlum, chief executive of Back on My Feet — the group whose volunteers helped Duncan start running — says that beyond the physical benefits, running shows that you can set, and then meet, a goal. “There’s hard work that’s needed to get from mile to mile, and no one gets to mile five instantly, but when you look back, you can see what you’ve put in and what you can accomplish,” Mahlum says.

Mahlum founded the group in 2007 in Philadelphia to help people living in homeless shelters. As a teenager, she had turned to running to escape an addict father at home. Often her route would take her past a homeless shelter where a group of men would cheer her on. After some successful runs, Mahlum went back to the shelter and offered to put together a running program.

Back on My Feet now has chapters in 10 cities, where they also help runners find permanent homes and jobs.

Fighting drugs and alcohol

Run to Recover, an online community and resource for people recovering from emotional and physical pain, was founded by Matt Klein. Like Mahlum, he used running to deal with his own problems, in his case drug and alcohol addiction. The group now counts more than 600 members. Newcomers who sign onto the group’s Facebook page find themselves quickly tapped with welcome messages from other members of the group.

“A run, no matter how long, has a beginning, middle and end. A start and a finish. Each run is a mini-battle and a major accomplishment,” says Klein, who regularly runs marathons and Ironman races. “That’s a great feeling and a true victory. It doesn’t matter if you are recovering from a terrible storm, the loss of a loved one, the death of a pet, depression, postpartum depression, a traumatic injury, post-traumatic stress or a chemical dependency.”

Alex’s Lemonade Stand Foundation, named for Alex Scott, who received a diagnosis of brain cancer at age 4 and died when she was 8, sponsors and supports races for family members of kids with cancer. The races help family members cope with stress as well as raise money for research. The organization has raised $60 million and holds a top ranking from Charity Navigator, which vets charities.

To help runners, it has hired trainers for one-on-one or virtual training sessions and has found that the benefits go far beyond raising funds. “Especially for parents of kids with cancer, running gives them an outlet for their pent-up energy and anger,” says Jay Scott, Alex’s father, a runner and co-executive director of the foundation.

Running partners

Achilles International partners able-bodied runners with disabled ones. Katie Sweeney, 53, and her son, Dusty, 15, who is autistic, run every week in New York’s Central Park with volunteer Paula Sen, 25. Dusty will be running his fifth race, the Achilles Hope & Possibility 5-Miler, in June.

Sweeney ticks off a list of benefits the program has brought her and her son, including the opportunity to share her passion for running, something she hadn’t even dreamed of before she was introduced to Achilles. She says other advantages for Dusty include increased fitness — important because some of the drugs he takes can lead to weight gain — and the “proud face” that Dusty, who has low communications skills, sports when he’s running.

Achilles, founded by Dick Traum, who lost his leg in a car accident and was the first amputee to run the New York City Marathon, is developing a Boston chapter for victims of the marathon bombing there who may want to use running as part of their recovery.

James Rimmer, 57, the head of the National Center on Physical Activity and Disability at the University of Alabama at Birmingham, says it’s not surprising that groups use running to fix or ameliorate life problems. Regular running works as “an anchor to a life that could be, at times, in disarray,” he says, “but when you’ve got that one anchor every single day, when you accomplish that one goal, there’s nothing like the feeling of accomplishment.”

Which makes Walter Barrera, 31, a perfect case study. Almost since he began running competitively three years ago, Barrera has had a serious goal: competing in a 100-mile race that he hopes to complete in no more than 36 hours. Barrera did much of his initial training with Back on My Feet while living in a homeless shelter in Northwest Washington.

He finds the prospect of the race exciting rather than daunting. After all, he has faced tougher challenges. Drugs and alcohol use cost him his job and his home. He now lives in his own apartment and works at a running store, changes that he credits directly to running and Back on My Feet. Eventually, he’d like to become a race-event planner.

“When I signed up with Back on My Feet, I thought it would give me something to do,” he says. “I never thought I’d get a life even better than the one I’d had before.”

Kritz is a health writer living in Silver Spring.