An amazing free ebook called Brain Over Brawn is one of the best things I've ever read on this subject, and continues to include all the big conclusions articles like these come to: http://brainoverbrawn.com/get-the-book/

I highly suggest giving it a a read or scan. It's very well written (fun to read, he's a great writer), short, and very to the point. He applies the 80/20 rule to working out, your body, your diet, and so forth.

My favorite section is how to build what he calls an "engineer bag", which costs a total of around $10 and replacing pretty much all gym equipment.