I ran 18 miles at 5:50 pace on my new treadmill (a peloton) this morning. I know treadmill running is lame, but I had to stay home and watch the kids while my wife ran some errands. That is about the pace of my marathon PR, but it didn’t feel extremely difficult. I ran it at 1.5% incline. I’m wondering, is that accurate at all? Can you trust a treadmill or is it always significantly easier than outside?