I heard like doing squats and lifting legs give your upper body more overall mass. I was just wondering if this had and truth to it or what the deal was.... thanks..
It is true.
Squats and deadlifts cause the body to release testosterone and growth hormone in the body, the testosterone is released and put into the blood stream and travels via the WHOLE entire body, blood doesn't just run through the lower body it's a continuos liquid that goes through your whole body.
Squats and deadlifts also provide a better stabilization of the bigger compounds, for example do you think a person with a stronger or lower back will have a better stabilization during a standing overhead press? Absolutely. When your press gets stronger, so does the ability to "push", as well as your anterior deltoids, chest and core. When those muscle groups gets stronger, so does your bench press, dips and other movements in which utilization of those muscle groups get stronger.
Lower body development can actually be the key to breaking plateaus towards the upper body, the testosterone produced by the exercises above is significant.