The limits of a mechanical metaphor

The chronicles tell of Neil Armstrong's dim view of exercise; to paraphrase: "The heart is a pump designed with a limited number of cycles; why would I want to reach its design limit earlier by increasing its beating rate?" As much as I consider Neil Armstrong a role model in many areas of life, we know better than that today. The heart is a muscle, not a mechanical pump. Assuming healthy genes, the heart muscle lasts longer if we exercise it.

And, as it turns out, lots of other organs seem to follow a similar behavior. Recent study after recent study (see the news release about a couple of them in earlier posts) shows that more exercise is better than less - all the way to 50 miles a week, and including knees - that joint sedentarians use to torture us runners psychologically. The studies show that sedentarian knees actually degrade *faster* than running knees. Like the heart, knees benefit from useage.

So go out, run and enjoy yourselves!