Okay, to counterbalance all the ire that's circulating amongst fitness freaks vis-a-vis the Times piece I wrote about here, below are two quick NYTimes links worth reading:

 

This one, on how to increase bone density through exercise, is interesting because it refines--to a significant degree--the common thinking on how bones respond to exercise.  When I got my CSCS certification, among the zillion facts I had to memorize was, more or less, that any force equal to about 1/10 of that required to break a bone would occasion bone reinforcement.  This "1/10" rule was a handy, round number that represented an approximation of the "Minimal Essential Strain" (or MES), which is, again, the "threshold stimulus that initiates new bone formation." 

Exercise which requires a person to support his or her body weight--with or without added resistance--was thought to be more effective for reaching the MES than exercises like cycling and swimming, which don't. 

Anyway, the article suggests that strength training isn't as effective at creating this MES as was previously thought.  Speed and power, it would appear, are essential components in reaching the MES (though they don't call it that).  Plyometric exercise--also known as Jumping up and down in various ways--fits the bill nicely. 

So if you're going for greater bone density--and who isn't in this age of osteo conditions--jump up and down like your life depended on it, because it just might.  Heck, it's a break from all that weighted squatting and lunging.

Another piece in the Times parses the science behind exercise and improved mood.  Researchers have found that rats who exercise stay calmer under stress than those who don't.  Interestingly, the "stress" they were exposed to--being submerged in cold water (ah, life as a lab rat...) was unrelated to their exercise regimen, running on a wheel or treadmill:  in other words, their stress-resistance wasn't only specific to the context of exercise; they just became more mellow rats. 

The stress-reducing changes wrought by exercise on the brain don’t happen overnight, however, as virtually every researcher agrees. In the University of Colorado experiments, for instance, rats that ran for only three weeks did not show much reduction in stress-induced anxiety, but those that ran for at least six weeks did. “Something happened between three and six weeks,” says Benjamin Greenwood, a research associate in the Department of Integrative Physiology at the University of Colorado, who helped conduct the experiments. Dr. Greenwood added that it was “not clear how that translates” into an exercise prescription for humans. We may require more weeks of working out, or maybe less. And no one has yet studied how intense the exercise needs to be. But the lesson, Dr. Greenwood says, is “don’t quit.” Keep running or cycling or swimming. (Animal experiments have focused exclusively on aerobic, endurance-type activities.) You may not feel a magical reduction of stress after your first jog, if you haven’t been exercising. But the molecular biochemical changes will begin, Dr. Greenwood says. And eventually, he says, they become “profound.”

I'm a pretty mellow guy and I exercise all the time.  My sister isn't and doesn't.  On days when I don't exercise I'm edgier and more irritable.  So my personal experience bears this out.  

So I'm a fairly even-keeled chappie, but I'm not sure that's necessarily a good thing, or a trait that makes me more likely to survive.  I tend to think it just makes me calmer as I head straight into disaster--like a cow going merrily to slaughter.