Hey, I'm 15, I weigh about 135 and i'm 5'8''.. I was looking for a workout routine to help me for my future in racing.. I will not be racing this year but I will be racing 125C next year. I consider myself to have an alright amount of muscle mass in my upper body, but thats not enough, I need more stamina and lower body strength. Right now, all I do is alot of perfect pushups.. Sets of them (14,10,6 Regular width, 14,10,6 Wide and 14,10,6) every other night with sets of crunches (30,30) I feel very toned when I'm done working out, but I know that upper body is not everything. I went to the Sandbox Arena and after one session I was wiped out. So I was wondering if you guys could give me a solid workout routine that involves cardiovascular and lower body to help me build up lots of endurance and strength. Keep in mind I have to muscle around a 220lb machine.