Retirees who do volunteer work in schools may help not only children but their own health as well, a study suggests.

Researchers at Johns Hopkins University in Baltimore found that older adults who served as mentors and tutors in their local elementary schools became more physically active in their daily lives.

Those who were sedentary before joining the volunteer program, called Experience Corps, more than doubled their physical activity levels during the school year, according to findings published online by the Journal of Urban Health.

The increase was not just a result of the volunteer program itself, the researchers found. Volunteers were more active in general, getting more household chores and gardening done, for example, while cutting down on TV time.

"They actually have more energy for their daily activities," said Dr. Erwin Tan, an assistant professor of geriatrics at Johns Hopkins and the study's lead author.

The activity boost was comparable to what's been found in clinical trials aimed at getting older adults to exercise, Tan told Reuters Health. In the case of the volunteer program, he noted, the improvement in physical activity is just one of the benefits.

The work offers both mental and social stimulation for older volunteers, Tan said, while children and schools benefit from the added help. Past research has found that the program improves children's reading skills.

For the current study, Tan and his colleagues randomly assigned 113 adults age 60 and older to either the Experience Corps program or a waiting list. Those in the volunteer program worked in a Baltimore public elementary school for 15 hours per week, where they helped children with their reading skills, problem solving, and cooperation.

After four to eight months, Tan's team found, volunteers were more likely than the comparison group to have bumped up their overall activity levels. They were burning 40 percent more calories each week, on average, while the comparison group expended fewer calories over time.

Most of the volunteers were low-income African Americans, a group at particular risk of low activity levels and chronic medical conditions like diabetes and high blood pressure. It's important, Tan said, that volunteer programs reach out to these older adults.

The Experience Corps program operates in 14 U.S. cities, including Boston, Chicago, New York, San Francisco and Washington, D.C.

"These schools are so eager to get the help," Tan said.

For older adults not inclined to return to school, Tan pointed out that there are many ways to volunteer and stay active after retirement. A national program called Senior Corps, he noted, connects older adults to a range of volunteer opportunities.