Exercise: A Guide from the National Institute on Aging
For the most part, when older people lose their ability to do things on their own, it doesn't happen just because they have aged. More likely, it is because they have become inactive. Older inactive adults lose ground in four areas that are important for staying healthy and independent: endurance, strength, balance, and flexibility.
Fortunately, research suggests that you can maintain or at least partly restore these four areas through exercise -- or through everyday physical activities (walking briskly or gardening, for example) that accomplish some of the same goals as exercise. What may seem like very small changes resulting from exercise and physical activity can have a big impact.