Hey after a long break I want to ride my bike again properly. Because I have problems with my back (Scheuermann) which pisses me off after every ride, because my damn back hurts like hell, it is furstrating and riding my bike does not make as much fun as it used to be. Now my back got a little bit better ofer the last year, but I still get pain. Also I am stuck on a boarding school and dont have many possibilities to ride my bike So my question is how do you train to improve your stammina and strength? What would you recommend to me? PS: there is no gym around here -_-