Hi Jake Green, I don't think 16 years old is too old to start boxing...go for it... apply yourself, and who knows, you might really like it. As far as gaining muscle mass, well I think lifting weights is the best for that(maybe get a gym membership instead of buying your own weights). Boxing is a great cardio exercise, but so are alot of things ie. swimming, running, bicycling etc. choose what you like... Jake Green I did want to say something because I read your thread...not everyone is cut out for boxing...but if you got "heart" that is one of the most important things in becoming a excellent boxer in my opinion. Cruiser