Walked for 5 mins then set the speed at 5.5 for an hour at 2.5 incline. This is as easy a run as I can do, and still, my heart rate gets up there. It does not feel that fast and my breathing was normal. Running outside, I can’t seem to string together more than 2.5km without taking a walk break. Pace outside is around 6:30-7:30/km. What can I do to get back my distance? My marathon PR from 2011 is 4:55:51.