Notes
Today was a "work" day, although my fastest average pace was only in the 8:20 range. I did a 2 mile warm-up at <158, then did 2x15 minutes at <172 with a 5 minute jog recovery. The ultimate goal of an even pace at that intensity was not realized, but I think it can be explained. The route was gentle downhill on the way out and gentle up on the way back, which affected pace. I think if I were to do this on a flat course, pace would be the same for both intervals.
After the "work" intervals, it was very tough to keep the HR down. It was only 65 when I went out, but it was mids 70s when I came back, and with the full sun on me, it felt very hot.