USA. Arizona. Sun City Poolside Exercise class. The outdoor group of the aerobic exercise club of Bell Centre. The average age is 83. Stretching and proper breathing is the most important exercise for senior citizens. Says Mila Gregor who set up the course in 1978 and has been running it, three times a week for an hour early in the morning, ever since. Never less than fifty turn up. At the time of shooting four members were over 90.