Regular exercise in middle age can help men and women hang on to their physical prowess as they grow older, a new study suggests.

UK researchers found that among 6,400 adults between the ages of 39 and 63, those who said they regularly exercised at the start of the study were more likely to be free of physical limitations nine years later.

While past studies have shown that staying active helps older people avoid disability, the new findings show that exercise is “equally important” for maintaining physical function earlier in life, according to the study authors.

“This study shows that regular physical activity appears to be critical to preserving high physical function in relatively fit, healthy, middle-aged men and women,” they report in the American Journal of Preventive Medicine.

For the study, Dr. Melvyn M. Hillsdon of University College London and his colleagues drew on data from a long-term health study of UK civil servants.

The men and women were deemed “sufficiently active” if, at the study’s outset, they reported getting at least 2.5 hours of moderate exercise or one hour of vigorous activity each week. Moderate exercise included activities such as biking and leisurely swimming, while vigorous exercise included swimming laps and running.

At follow-up nine years later, sufficiently active adults were less likely to have physical problems that kept them from playing sports, lifting heavy objects, or being able to perform routine activities like climbing stairs or bathing. More than half of the men and women who reported no physical limitations at follow-up had been adequately active at the start of the study.

Overall, however, Hillsdon’s team found that relatively few study participants were getting enough exercise - half of the men, and about one quarter of the women. Moreover, the large majority of both men and women had at least some physical limitations by the end of the study.

In the absence of chronic illness, the researchers note, the most likely reason for such physical decline is the progressive loss of muscle mass and strength - a normal part of aging that may start as early as age 30.

Given this, there is a “strong argument,” Hillsdon and his colleagues write, for staying active throughout life to minimize muscle loss.

SOURCE: American Journal of Preventive Medicine, April 2005.