Trends

I was looking at my exercise pattern trying to see if I can guess how I was going to do on any particular day. I discovered this view on the Nike+ site that shows my walk/jog history (short term) and several things stand out to me. First, roughly every third day seems to be a good day for distance and second, there has been a gradual increase in my distances. There has been a corresponding increase in time spent on the treadmill which means that my speed hasn't increased significantly. I guess I knew that since speed is set on the treadmill. I've been reluctant to go much faster since everything that I've read recently has indicated that we should exercise at about a 60% to 80% of our mazimum hear rate. When I'm running, I tend to be at 80% to 90% already. So is this recommendation based on real science or is it just what everybody has been saying for forever? For myself, I've stayed at the 90% value for literally hours and it doesn't seem to have hurt me or am I just fooling myself? Anyway, that is why I have been reluctant to go any faster. What I really need to do is get off of the treadmill and go outside.