when you stand on your pedals are you just letting your body weight do the work? or are you using your body weight as well as leg extension (ie muscle force) to do the work. How do you think Robbie McEwen can out sprint me when he is 150 lbs and I"m 250lbs. If it was just body weight on the down force I would kick his a$$...you have to factor in the force of the downstroke (which is much larger than the force of the weight) as well as the weight.