Q: how young can you be to start weight training

A: You can and should be physically active at all ages. Weight training specifically you can start early too (as young as 12), BUT you must be responsible around weights, have an adult supervise and spot you, and most importantly use only light or moderate weights and not push yourself too hard till you're at least 16. The reason is that a serious unjury at young age can stunt your growth! So while there's nothing wrong with weight training when young, you should always always always put safety first.