I can tell you I can stand to pedal but not continuous for more than about 40 revs, Has nothing to do with fitness my legs just tighten and I think it is related to my running dystonia. I can sit back down for a a few cranks then get up and repeat it but I cannot just stand and pedal non stop for the distance many are claiming. It really does not make me slower than others it is just I lack with specific ability. I might also add on an unrelated note I don't ride no hands either. I probably could practice and do it a bit but why. I would not feel safe. When I was 12 years old that was a different story could do it with ease.