Was surfin the net and found this really great article. In it the author states that in as little as 15 secs per muscle group, you can build and/or preserve muscle through weight bearing exercises:

http://www.naturalnews.com/011285.html

I believe this to be true, because I've only started weight training 2 weeks ago for about 2 days per week (1 upper/1 lower body). I already SEE progress. Also, I've been playing around with my pull up bar every other day. I went from ZERO pullups to 3!!! I think it's amazing how fast you can see results weight training with little effort! Hopefully, this article can motivate someone else to JUST DO IT!

Happy reading!

Congrats on the pull-ups, that's awesome!