I'm all about this whole mind-body thing of late; call me a freaky Eastern-religion nut from Mars if you will, but I'm utterly convinced that there's more to this whole exercise thing than building yourself a six-pack.  If there weren't, there's no way I would have stuck with it so long. 

A mounting body of evidence seems to be suggesting that it's true:  work your body (in certain select ways) and you do work your mind, often in very beneficial ways.

According to a Scientific American piece I just read, unlike what we learned as kids ("Don't drink: it kills brain cells and they NEVER grow back!") we're always generating new brain cells--the real question is, what happens next?  Do those brain cells stick around, or do they say, much like the 'extra man' or two that always seems to be hanging out at every work site I've ever seen or worked on, "Looks like you guys have this pretty well under control here, no need for me to stick around..." and simply slink away? 

...the production [of new brain cells] can be influenced by a number of different environmental factors. For example, alcohol consumption has been shown to retard the generation of new brain cells. And their birth rate can be enhanced by exercise. Rats and mice that log time on a running wheel can kick out twice as many new cells as mice that lead a more sedentary life. Even eating blueberries seems to goose the ­generation of new neurons in the rat hippocampus.

So a handful of factors (exercise among them, duly noted) seem to influence neurogenesis (learning new lingo all the time!)--but again, what makes these cells stick around?  The answer appears to be "learning new stuff."  But not just ANY new stuff; it appears that, in rats, anyway, the new stuff needs to be relatively challenging:

....When learning is difficult, neurons throughout the hippocampus—including the new recruits—are fully engaged. And these recruits survive. But if the animal is not challenged, the new neurons lack the stimulation they need to survive and then simply fade away.

The line between an activity that makes brain cells stick around can be seemingly arbitrary, though:  a somewhat challenging swimming exercise didn't really do it, but an exercise that taught the rats to anticipate a stimulus to the eye (the author compares the test to the Pavlovian one in which dogs learned to anticipate the arrival of dinner based on the ringing of a bell) stimulated those new brain cells, giving them a job to do and making them hang out a little longer.

(Looks an awful lot like a bunch of cubicles.  Coincidence?)

All this is to say:  I'm even more convinced that it's not just exercise that makes you smarter but learning new things, challenging your body in NEW ways that optimally stimulates the brain.  Biologically, it appears that we're wired to conserve energy--presumably because historically, that energy has been hard to come by.  But nowadays it ain't:  just swing by your local In-N-Out and see how many calories five bucks will buy ya.  So the challenge these days is to figure out new and interesting ways to keep ourselves alive by burning energy.

So if you're still stuck on your old, tired exercise plan, here's yet more incentive to change it up. 

Here's a quick brain-cell preserving activity:  circle one arm forwards while circling the other one backwards.  Now switch it.

They say you can’t teach an old dog new tricks, and certainly as adults, many of us find it painful to learn something completely new. But if we want to keep our brains in shape, it probably would not hurt to learn a new language, take up tap dancing, or tackle some fast gaming after your Wii Fit workout—and it might even help.