My cat's in the upper teens. Which is bordering on death's door for a human. I have to make a point of sneaking out if I'm walking to the store because he'll follow me and I don't want to risk him getting hit by a car. Those tiny cat feet and tiny cat gait, at a human age of around 90 or so, manage a mile pretty easily. It's mind blowing to think that humans with something like ten times that gait and in the prime of their youth would find it offputting.