I am not sure, but today I did 15km's in the mountains and it kicked my butt! I've never done much more then 10~15Km's on the road either but wow, I am sore! shoulders, legs, arms... wow. I feel great! Not sure the elite would consider it a mountain but it was quite steep (for me at least) I had to step off a couple of times but surprisingly I managed most of it on the saddle. I am trying to remain seated, I remember, when we were younger, we would stand up and pump like mad kids but franlky, I am not sure that the equipment would stand up to that today. But I also remember that most of my friends who were well in to MTB'ing always said that staying in the saddle is the way to go.