I decided to run in my triple black ERs with the two holes and fastest carbon fiber plate to see if I could beat my 5K PR from yesterday in VaporFlys. My long term data shows about 4% faster than average times for my VFs, and anywhere from 4-8% improvement from my ERs with custom CF plate. I did beat yesterday's time, but only by a little bit and my average HR was a bit higher, so I consider it a wash. Today's run was very different than yesterday's however. Yesterday's run in the VFs was very consistent throughout the whole run. Pace and HR curves vs distance were perfectly flat. Today's run in my ER with CF plate began 8% faster holding a HR of 160bpm. So I thought I would smash yesterday's record. But halfway through the run I felt the "propel you forward feeling" of the shoes go away. My pace then fell to 0% faster than average (4% less than VF) for the last half of run still holding a HR of 160bpm. Typically this is just due to muscle fatigue as my fastest CF plates need the muscles to load them up during each stride. But this time my muscles were not fatigued at all. The plates just went limp. I think I might have finally found the fatigue threshold of these springy plates after well over 100 miles of running and trail hikes. Not sure yet.