Standing takes a lot more energy than sitting - remember, the challenge is coming down again as well on each lap, but even on the uphill not having to support f

Standing takes a lot more energy than sitting - remember, the challenge is coming down again as well on each lap, but even on the uphill not having to support full bodyweight is an advantage, instead you just push with the effort you require on the pedals. And of course if you are in the wrong gear a bicycle will be ineffective... that's why you choose the right gear?