As America ages, more studies are being done on how activity can help reduce the impact of illness and chronic disease. Research shows both physical and mental exercise is a kind of medicine for older adults. 90-year old John Murray lives with his wife, in a senior living community near Syracuse. On any given Monday, he takes part in four different programs. "At least one of them is water aerobics, another is another physical," said Murray. "A third is a tai chi type of operation, and a fourth