It had been thought that walking was sufficient. In fact, walking is known to help stave off a number of common health problems that the elderly normally face, such as diabetes, arthritis, heart disease, and more. A noted problem, however, is that walking speed tends to decrease with age and the benefits decrease with it. This means that seniors will eventually slow down, and the effects of old age increase.
Running, on the other hand, has a number of additional benefits. These are results that are greater in effect than what walking can produce, and some of them cannot be produced by running at all. Flavio Maluf says he likes running because by running one obtaines a greater discipline, better weight loss control, the prevention of muscle and bone loss, and the boost of your ability to fight disease. There really are a lot more, too.
Perhaps the greatest benefit, that was noted, however, is that an older runner has the ability to move and walk at about the same rate as a more sedate college student. This is probably the result of mitochondrial changes in the cells themselves, which enables them to get more energy at a slower rate, or with less work.