Humans aren't cars...? Don't use an analogy unless it has a logical basis.

Parts of the analogy are certainly correct...

Mechanical parts wear out from use, whether they are animal or machine. Animal parts will heal to an extent and may require a minimum level of use to stay healthy, but they still wear out.

You're right. It is much easier to repair a car.

Car's don't self repair.

If I go lift heavy weights, my bones self repair and get stronger.

If I sit on my butt all day on a computer, my bones get thinner and weaker.

No matter how much you drive a car, it is never going to get "stronger", only slowly wear out.

Since you are a human and not a car, I would suggest you maintain your body like it is alive and not made of metal.

In both cars and people I would ask the same thing: is there a 25-35000 miles option too ? Too low is worse, and 20 is a sure indicator of big problems. So is 200,000.

As to the general feeling here. I invite everyone here who thinks ridiculous exercise is good to volunteer at an emergency room for a week. I guarantee this idea will get cured on the first day in any large city.

Humans are cars that run constantly. So the human analogy to a car with 20 miles would be a baby.