When I was younger, I ran a couple of miles most days and often a 5K or more on weekends. Later, I turned to indoor soccer and kicked a ball around once or twice a week. I fully subscribed to the mantra of “no pain, no gain.” Turns out it was pain that made me stop, first from an arthritis-fueled bum knee and then eventually from a broken hip. But now there is new thinking about exercise – and it applies as early as the 50s and continues well into the 70s.