According to a recent AP article, "the three-year survival rate was about three times higher for active 85-year-olds compared with those who were inactive." Even among individuals who had previously been sedentary, exercise proved beneficial.
The article makes an important point: It's possible "that participants who were able to exercise were already healthier, and thus likely to live longer." Although the study can't positively rule this out, experts argue that the link between activity and longevity is valid.
If exercise can benefit people in their 80s, imagine what it can do for the rest of us?