Dr. Robert Klapper, an orthopedic surgeon and host of ESPN’s Weekend Warrior radio show and podcast, says that “exercise comes in two flavors—nurturing and abusive.” Unfortunately, a lot of the sports that people love—such as pickleball, tennis and basketball—qualify as “abusive” because of the wear to the body. In that case, you should complement the sport with gentle strengthening practices such as pool exercises, riding a stationary bike, yoga, Pilates or tai chi. Klapper, 68, gets up twice a week before sunrise to surf.