I'm a junior racer too. In fact I am in the same exact position as you. And I keep contemplating on whether or not to bulk up above the waist. So here is my take on it...Muscle grows by tearing it, the more power you put on your muscles, the more they tear. Now when they repair the strand of muscle that was torn will regrow along with a new strand. Key phrase there was that when muscle is under continued stress/power it will rebuild into bigger muscle. So if we look at the top cyclist they don't have big upper body strength. Why? Because throughout training and races on the bike, they dont have as much need for the muscles performance speaking. Therefore they won't improve your performance. Sure they might decrease neck pains. But since you and I are juniors we don't experience back or neck pain, yet.