Regular exercise, including walking, significantly reduces the chance that a frail older person will become physically disabled, according to one of the largest and longest-running studies of its kind to date. The results, published on Tuesday in the journal JAMA, reinforce the necessity of frequent physical activity for our aging parents, grandparents and, of course, ourselves. While everyone knows that exercise is a good idea, whatever your age, the hard, scientific evidence about its benefits in the old and infirm has been surprisingly limited.

“For the first time, we have directly shown that exercise can effectively lessen or prevent the development of physical disability in a population of extremely vulnerable elderly people,” said Dr. Marco Pahor, the director of the Institute on Aging at the University of Florida in Gainesville and the lead author of the study. Countless epidemiological studies have found a strong correlation between physical activity in advanced age and a longer, healthier life. But such studies can’t prove that exercise improves older people’s health, only that healthy older people exercise.

Other small-scale, randomized experiments have persuasively established a causal link between exercise and healthy aging. But the scope of these experiments has generally been narrow, showing, for instance, that older people can improve their muscle strength with weight training or their endurance capacity with walking.

The exercise group received information about aging but also started a program of walking and light, lower-body weight training with ankle weights, going to the research center twice a week for supervised group walks on a track, with the walks growing progressively longer. They were also asked to complete three or four more exercise sessions at home, aiming for a total of 150 minutes of walking and about three 10-minute sessions of weight-training exercises each week.

Most of the volunteers “tolerated the exercise program very well,” Dr. Pahor said, but the results did raise some flags. More volunteers in the exercise group wound up hospitalized during the study than did the participants in the education group, possibly because their vital signs were checked far more often, the researchers say. The exercise regimen may also have “unmasked” underlying medical conditions, Dr. Pahor said, although he does not feel that the exercise itself led to hospital stays.

Dr. Pahor cautioned that the LIFE study is not meant to prompt elderly people to begin solo, unsupervised exercise. “Medical supervision is important,” he said. Talk with your doctor and try to find an exercise group, he said, adding, “The social aspect is important.”

Mildred Johnston, 82, a retired office worker in Gainesville who volunteered for the LIFE trial, has kept up weekly walks with two of the other volunteers she met during the study.“Exercising has changed my whole aspect on what aging means,” she said. “It’s not about how much help you need from other people now. It’s more about what I can do for myself.” Besides, she said, gossiping during her group walks “really keeps you engaged with life.”

NY Times