At CIM, I went out at what I felt was a completely sustainable pace. I barely felt the strain, running along with the crowd, not thinking about deadlines, until I got to the 5 km point and looked at my Garmin and saw I was right on schedule (despite the conditions). This wasn't bad, because there were headwind sections ahead, and this preserved my buffer against Boston qualifying for when I'd likely really need it.
Yet despite this my legs let me down and my pace faded, first at 17 miles, but then further at 20 miles, although I seemed to limit the explicit damage to two discrete steps, rather than a steady decay into oblivion.
Here are my splits against Ron, a coworker and an experienced marathoner who usually runs sub-3 hours. I view him as a good model, someone clearly faster than me but not so much so he's in a completely different class:
first second third fourth total Ron: 00:40:31 00:51:04 00:47:59 00:45:14 03:04:36 Me: 00:42:50 00:54:37 00:54:11 00:53:12 03:25:34 delta: 2:29 3:33 6:12 6:58 21:02
Okay, now me versus the top woman (I use women because the times are a bit more comparable, and she, like I, had ample draft opportunity):
Alisha: 00:33:40 00:43:47 00:40:30 00:36:58 02:34:57 Me: 00:42:50 00:54:37 00:54:11 00:53:12 03:25:34 delta: 9:10 10:50 13:41 16:14 50:37
The trend was similar.
At the start I was quickly dropped by the 3:10 and 3:15 pacers. I didn't pressure myself to stay with them, figuring if I kept them ahead of me I'd be fine. But it turned out I did actually pass the 3:15 pacer -- somehow I didn't notice... then he passed me and again I didn't notice:
Peter : 00:43:26 00:53:23 00:50:57 00:47:12 03:14:59 Me: 00:42:50 00:54:37 00:54:11 00:53:12 03:25:34 delta: -0:36 1:14 3:14 6:00 10:35
Here's my time against the 3:10 pacer:
Michael : 00:42:23 00:52:55 00:50:21 00:44:26 03:09:49 Me: 00:42:50 00:54:37 00:54:11 00:53:12 03:25:34 delta: 0:27 1:42 3:50 8:46 15:45
They dropped me and I never caught them.
And here's my time against the 3:25 pacer. He passed me quite late, but again I never noticed.
Lee: 00:45:37 00:56:52 00:54:02 00:48:46 03:24:39 Me: 00:42:50 00:54:37 00:54:11 00:53:12 03:25:34 delta: -2:47 -2:15 0:09 4:26 0:55
Pretty amazing I never saw any of the pacers in three separate encounters with them. It was quite crowded near the start, but after that thinned out a bit.
But the overall trend is clear: given my final time, I went out too hard. I should have dialed back my perceived exertion even further. Yet had I paid more attention to my Garmin I would have run the same pace anyway, as it was close to my target. Indeed I had thought I might be able to follow the pace of the 3:10 group. The last time I was in this sort of situation, in the San Francisco Giants Half last year, I was able to stick with a "reach group"s (7-minute mile) pace (they went faster, but I ended up right at 7-minutes). This year my "reach" group was 3:10, my "should be safe" group was 3:15, and my "safety net" was 3:25. I made a mistake letting myself pass the 3:15 group (which I didn't notice in the crowd) but I doubt that made the difference. I need to digest these results and replan for my next one.