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A daily 20-minute walk can help older adults reduce the risk of losing the ability to walk without assistance, thereby enhancing the quality of their later years, a U.S. study said Tuesday.

The study, published in the Journal of the American Medical Association, found that moderate exercise including walking can help aging adults maintain their mobility, or the ability to walk without assistance, at a rate 18 percent higher than older adults who did not exercise

Called the Lifestyle Interventions and Independence for Elders (LIFE) trial, the study recruited 1,635 sedentary men and women aged 70 to 89 to investigate how daily physical activity will prevent older adults' loss of mobility, defined in the study as the ability to walk 400 meters, or about a quarter of a mile.

Although 400 meters might sound like an arbitrary number, it's an important figure for older adults, according to the study led by researchers at the University of Florida (UF).

"Four hundred meters is once around the track, or from the parking lot to the store, or two or three blocks around your neighborhood," Co-principal investigator Jack Guralnik, professor of the University of Maryland who also holds a faculty position at UF. "It's an important distance in maintaining an independent life. "

The participants in the study could walk a quarter mile within 15 minutes but were at risk of losing that ability. Low physical performance is common in older adults and is a risk factor for illness, hospitalization, disability, and death.