to be honest with you i'd wait a couple of years before you go to the gym an do resistance, just ride more you'll soon get stronger, or do core exercises like press-ups, ab-curls, chins, lunges, squats (circuits are good), because where weights are concerned your still abit young an not fully developed, i'd say wait till your 16. i see it in my gym to many kids trying to get stronger at 14 an abit under, its silly they should be outside playing sports, an they don't develop like a full-grown adult would, thats my opinion as a fitness instructor though. if u still decide to go make sure you get advice an help, an dont push your boundaries yet untill your atleast 16-17. up to you if you take my advice, but i know what i'm talking about, hope this helps you alex, cheers ben g