Nice piece on Runnersworld.com about the effect of running on a man's private parts. I read it of course, because I'm a dude and it's in my best interests to know as much as possible on things that might impact the center of the known universe. Suffice to say that running is good for the plumbing in almost every way. The only down side comes from running an average of more than 67 miles per week. As I haven't hit 67 miles per week since sometime in 1981, that does not seem to be an issue for me.
Of course, the connection between running and being master of your domain has been known for a long time. I remember back when I ran my first Bay to Breakers at the age of 13, seeing a finish line vendor selling bumper stickers reading "Runners Keep It Up Longer." Taking those words at face value, knowing there could be a dual meaning but not knowing precisely what it might be, I asked my mother for a dollar to buy one. I figured that dressing up the Country Squire with a little pro-running badinage couldn't hurt. This is when I got an advanced lecture on the birds and bees from my embarrassed mother.
Bottom line is that I have yet to see a valid reason not to run. Your mind is sharper for longer, your body gets lean, your heart works better, and the boys keep on rocking and rolling, thanks to the increased blood circulation. It's all good. Makes you wonder why any man, of any age, wouldn't take up running.