My grandfather, my mother's father, was quite the athlete. He played tennis and rode his bike into, I think, his seventies (unfortunately, he got into a car accident in Golden Gate Park and that ended his bike riding days; he lived into his nineties). My mom has been occasionally riding an old yellow bike of Charlie's; she's got a kind of natural coordination some of which I've inherited and Charlie too.
So you're going to ask, why don't I get on the yellow bike at other times and ride!
I have been known to take a little spin around the block; it's definitely fun and takes me back to my grad student days when I rode a bike all over New Haven and its environs. At the moment, Jim and I continue to divvy up our energies: He does the bikes (over 23 miles on Friday including a Jersey horse country bike path ride) and I'm on the ground control (mileage from two race-walk pace jaunts -- Charlie doesn't stroll, he does a very accelerated walk-pace, enabling me to run at a decent pace up a hill, with four books and two coffee thermoses, at work to be on time for 8am Latin class).