I keep running into more and more positive evidence, and I think it's having the effect of making me believe exercise really is healthy. Now it's time to think about what it means. If increasing wear and tear in the muscles (and bones?) helps, it must be true for the brain as well, and indeed, we all know the famous "use it or lose it" about the brain.
So if we generalize and conclude that our bodies maintain best what we use the most, what does that imply? Clearly, we should use our brains as much as possible (that seems to be obvious anyway), and exercise with emphasis on variety (different kinds of cardio and weights, different intensities). What else? Should we expose ourselves to multiple pathogens to maintain our immune systems?
What do you know, when I started I didn't know where I was going with this, and here I end up again with hormesis. Well, it's good to be consistent.