Second, my goal was too ambitious given my training window. Having studied my heart rate and Garmin data, I now realize my heart was beating like a bunny on the back half. I compared it to the Scotland Run (2 minutes slower), and I was probably 7% higher on back side. I was running north of 90% HRM for almost all of miles 4-6. That is very hard. Part of that was because of my fast first half. (My 5K split was 22:40, which is really amazing for me, but way, way too fast if my goal was a 47:00 10K.)
Here is a SportTracks graph of the run. Any heart rate above 170 is in Zone 5, the 90%+ zone, and I was running at 180+ almost from the bottom of the Harlem Hill (mile 3) until the finish. HR is the pink shaded area; pace in blue; elevation in yellow on bottom.
In sum, my heart rate simply did not drop after the hill climb at the end of Mile 4, and continued at 180+ for almost 2 miles. And then I bonked in Mile 5.
What I am most disappointed in myself is that I had to take two short walk breaks in mile 5. (They are shown by the big blue spikes in pace during mile 5.) Looking at my data, they totaled about 1:30. I always have the fear in a race that "Hey, I am not going to make it, I can't do it" and then have to stop. And for me taking a walk break is about as bad as it gets. (I have never had to stop a race.) I had to walk in the NYRR 8000 on Mar 15, when I was totally out of shape. Before that, the last time I walked in a race was the 2007 Grete's Great Gallop half-marathon. (That race was on a very warm October weekend, the day before the 2007 Chicago Marathon that had all of the heat issues.) Anyway, looking at my Garmin data, I realize my heart rate was crazy, and it is no wonder I had to stop. Just before I stopped, I was at 94% of max just trying to cruise (albeit at 7:30 pace).
What I really should have done was follow my Garmy. I'll be honest, I wasn't paying attention to heart rates after I got up Harlem Hill. It was just numbers and rain and following the people I was with and being impressed with my split and I don't know. I was focused on just trying to get home and race with the crowd. But I look back at the data, and my heart rate never really recovered. So I was running with a HR north of 90% max, which I did for 15+ minutes until I cracked in mile 5. Trust Garmin. I should have slowed down, brought HR down, and I still would have made it in my goal. Smarter racing, better pacing and experience will get me there.
So it is back to original plan and original goal -- run a 60 AG time at Father's Day 5M on June 21. Smart training and smart racing....