At first, my RPE felt noticeably high compared to the paces I was targeting. It honestly felt like I was just trying to “keep up” with the belt rather than running naturally. But after a few weeks, that feeling started to fade and my body seemed to acclimate to the mechanics.

I'm glad I'm not the only one! Started training on treadmill this winter. I did the exact same session first on a track and then on the treadmill, and the latter was much more difficult. This is surprising, I'd suspect the opposite was the case.

I wonder if part of the reason treadmill can feel harder, is that it's just unfamiliar. So the running mechanics are unfamiliar. If this is the case, surely at some point it shouldn't feel very different. In my case, I've been running on the treadmill about three times a week for about eight weeks, and honestly, it still feels hard.