Originally Posted by jur
Hmmm, I wonder... If you are in the saddle, then the geometry of rider/bike is constant, that tells me the same muscles are used. If you are standing on the pedals, I guess the rider will be leaning slightly forward compared to a flat riding position, so his arm geometry would be different but wouldn't the leg and body geometry be the same again? Especially for a rider who is very conditioned, they would automatically adopt a position which is essentially the same for both conditions so as to get maximum effort?
I like chanmans explanation better but anyway.. you move in your saddle to keep you upright, as the bike is on an incline.. Even if you are conditioned, you are talking about a bunch of musles, not one single muscle. Power is derived from different muscle groups in different positions..