The act of moving lots of weight around in an effort to gain bigger muscles and become buff. Can be very healthy in moderation, but in excess, can result in a decrease of brain mass.

I don't like the idea of working out just to work out.
Sure, in moderation it will help make your heart run smoother, lungs breathe easier, and possibly live longer...
But I just can't stand the idea of sitting inside flexing for no other purpose.

Why not go roller skating or jogging outside?
Look up at that blue thing called a sky
at the green grass and trees,
at nature.
Or flex your muscles moving furniture for the old lady next door? Maybe even make a few bucks while getting the same exercise.

Theres gotta be something useful you could be doing with that work out besides pushing metal bars back and forth.

Working out has many benefits to the true geek. Not only does it dispell the meek stereotype, at least in my case there are many times when physical strength comes in handy. Ever moved 5 server towers from one end of campus to the other? Or just carried a monitor to another room? The stronger you are, the more stable you are - less broken hardware.
Also, I have noticed that I become more confident as I work out more. Both socially and on a physical level (my hands don't shake as much when soldering.)