It seems like when you walk through a gym these days, everyone is huddled around the free weights doing arms, while there is no one to be seen at the squat rack. Men often decide to forgo any leg training and just concentrate on their upper bodies. They figure that since they went for a run that morning or did some interval training on the bike the day before, they have already worked their legs enough.
The truth is that working your legs will indirectly help your upper body grow. Your leg muscles are incredibly large; when stimulated, they release a large amount of testosterone — the primary anabolic hormone responsible for muscle growth — throughout the body. Thus, you will benefit your upper body on days you don’t even work it out.
Also, having a strong lower body is the best basis for the rest of your training. Otherwise, it is like trying to build a house without a foundation — not very effective. So be sure you don’t pass up your leg training sessions any longer.