Horse-faced space dog
since i started riding my carido and breathing have improved slightly but not nearly enough. when i ride at allaire i can usually keep riding for quite sometime before i need to stop. i never really have issues with running out of leg strength. but when i go to places that have some pretty strong climbs i run out of lungs pretty quickly and my heart races like nuts. is there anything i can do to help increase my cardio? some have suggested i run but i have a crappy knee that doesnt cooperate while running. any suggestions would be awesome and thanks in advance.