Well shoot. I thought I had planned everything so perfectly. I ran around the Island in my flats today. It was only my third time wearing the shoes. The first time I ran 3.5 and the second time was Friday's 5k. I ran around the Island just fine, I wasn't concerned about injuries but I honestly didn't feel that great. I hit 1:18:00 (5:47 pace) which is obviously quite fast and it should have felt hard, but I have run as fast or faster than that in trainers a couple of times.
Moreover, I did not like the way I passed myself. I ran fairly easy to begin with, then when I tried to pick it up I did not feel good and my pace started to go all over the place. (Including one 800m section in 3:30!). I ran 14:32 for the last section (5:55 pace). This is definitely pretty good as it is a little bit hilly but I ran faster than that closing out my 20miler and I consistently finish of 10mile runs faster than that. I basically felt that my form became quite inefficient running in flat after I got to about 10miles and that I was not receiving any benefit from them. Not only that, I ran to fast at the beginning using a running form that I was not accustomed to, leaving me tired at the end. It may have simply been a bad day, but I know what it feels like when I get tired and this felt weird, completely unlike running a comparable effort in trainers. How my body will react going past 16,17 miles is unknown to me, and I have no time left to find out before the marathon.
In conclusion, flats will have to wait for another time and I will have to integrate them fully into my marathon training (something that seemed like it would be dangerous this year, but now I've run 13miles in them, I don't think I need to worry about it). I weighed my shoes on an old fashioned scale this afternoon. My trainers weigh 5 ounces more than my flats. Using the rule of thumb: 1 second per ounce per mile, wearing trainers will slow me by 2:10 in a marathon. So be it! I know how easy it is to lose two minutes in the last couple of miles of a marathon, I need to make sure I feel good!
Late afternoon 3.5 miles.