WASHINGTON — It’s not too late to get moving: Simple physical activity — mostly walking — helped high-risk seniors stay mobile after disability-inducing ailments even if, at 70 and beyond, they’d long been couch potatoes. One health policy specialist said a study released Monday suggests prescribing exercise may be just as important as prescribing medications. “Once you lose that mobility piece of your life, then you really lose independence,” said Patricia Katz of the University of California, San Francisco, who wasn’t part of the new research but said physicians need to put the findings to use. Katz called it striking that among the walkers, “if you start to have problems, you have a greater ability to recover and get your functioning back.” Older adults often shift back and forth between independence and conditions that can be disabling at least temporarily — a broken bone, an operation or a hospitalization from illness that requires time and rehab if they’re to get back on their feet. Monday’s research examined whether regular physical activity could help even the oldest seniors stay mobile for longer despite other health conditions. The study enrolled more than 1,600 adults between the ages of 70 and 89 considered at high risk for disability because they were sedentary and had various chronic health problems, such as heart disease or diabetes.