My own take has been finding it harder to ride. I started running at about 10 and ran on track teams for many years. I always passed lots of people when it came to the uphill. So much so that it drove my coaches nuts. If I had that much energy up the hill, why didn't I use it over the whole course. (cause I didn't know I had that energy )

I have yet to be yelled at for having too much energy riding up a hill.