Somewhat related as you mentioned swimming and cycling, but both of those forms of exercise can lead to decreased bone density unless you are supplementing them with walking or running. Cyclists in particular often have lower back problems from sitting with their back in a weird position for long periods of time. That's not to say they aren't good forms of exercise, but it is also good to get some sort of impact based exercise as well (like running or walking). Of course too much running is probably bad for your joints and anecdotally I know a lot of older runners with chronic injuries, so it's tough to strike the right balance.