When did your boys start working out to gain muscle? Are there downsides to starting too early? Stunting growth?

My 11 year old wants to start working out. He's very thin and on the shorter side. I'm wondering if he is too young to start things like lifting weights and whatnot. My oldest didn't really start putting on muscle until last year as a high school freshman and he was noticeably behind a lot of his friends. It was a clear disadvantage for sports. I coach high school lacrosse but for girls so I'm not sure if it's different for boys. I have heard the working out before puberty can stunt growth but others say it's a myth. Is there any truth to that? Should we discourage working out? via /r/Parenting https://ift.tt/2Lt4mQN