It turns out that exercising keeps us sharp. We don't really know how, but it's by either reducing BPM or increasing, the aptly named, noggin: read it here. At least it works for mice.
We often think that using mice in experiments are good proxies for understanding the ways that humans work. We used to think that beagles were sufficiently similar that they could be human experiment surrogates. That's now thought to be ridiculous (and too expensive). But we also used to think that animals didn't experience pain so that is ethically neutral to test on them (or it might be claimed it was morally imperative since we would make great leaps in science). It was always acknowledged that non-human animals have reflex reactions to situations that we would find painful, but that animals are physiological dissimilar. But this raises the dilemma - if they are physically dissimilar which makes it morally neutral to test on them, then we should not use them as proxies for understanding human physiology because the results of the test are bunk when applied to humans (a point thoroughly discussed by Bernard Rollin at CSU), or else we admit that they feel pain and admit there are moral issues to be raised, which might compromise animal-testing.
So we now think that mice (or rats) are representative of the basic physiology of humans when it has recently been noted that men are not even similar in some regards to women: women don't need as much protein and heart rate monitors now need to be updated since they don't adequately measure the ideal aerobic activity for women.
And we think that mice are like humans? Certainly, very smart scientists will claim something like: "but when it comes to neurological functions, we know that similar processes are at work so that they are generally analogous" or some other platitudinous rationalization. Mammalian brains are all fairly similar - true. But if we are just now figuring out that there are (large) physiological differences between the sexes of the same species that we have previously overlooked, what are we currently overlooking as differences between species?
Methods change, practices are updated and our base of knowledge slowly expands (room for debate), while our biases and ignorance continually blind us.