I heard, and I have no info on the accuracy, that squats naturally increase your hormonal levels of testosterone which helps with muscle building and all that jazz. No idea if it's true but it hasn't *not* worked for me soo..
I've not heard that particular theory but we always knew that if you want to increase your bench, get on the squat rack. Always figured it had something to do with blood flow & cardiovascular activity, etc. -- squats work the largest muscles in your body.
I've heard it and somewhat believe it. Again, because you are working so many muscles to do a squat (I've heard like 200 or something) it makes sense that you are going to improve testosterone production as you put on muscle mass.
Found this from the Men's Health article that I probably saw it in:
To beef up your testosterone levels, the bulk of your workout should involve "compound" weight-lifting exercises that train several large muscle groups, and not just one or two smaller muscles. For example, studies have shown that doing squats, bench presses or back rows increases testosterone more than doing biceps curls or triceps pushdowns, even though the effort may seem the same. This is why doing squats could help you build bigger biceps.