Notes
Noticed that my Garmin stopped at about 18.75, after missing just under a mile, so my splits after that are off. Still, the recorded splits tell the story. I had to slow down because my quads were not ready for the fast pace during the first half. My cardio endurance was not the problem, and I thought this would be my only limiting factor. I will prepare next time by doing more downhill running, thanks to the excellent article provided by Tall Dave.