I am a 15 year old n3rd, but i wanna get more into shape, since i found out my pulse is around 75-88, and i'm pretty sure thats not right. whenever i use my school gym i just love usin the excercise bike, and i was wonderin whether i should buy one. my sister wants to get a treadmill, but i can ride the bike for a couple of hours at a time (whilst reading too) - is an exercise bike right for me? what would you reccommend....