Sunday, March 27, 2011

The National Half Marathon: Pace Analysis

Yesterday's half marathon was disastrous in terms of my overall finishing time. My unofficial net time was 1:50:34 for an 8:27 pace. I've done nearly that pace in 20-mile training runs. But of course, there were extenuating circumstances. I fell hard just after I finished mile 1, dislocating my right shoulder. I was fortunate to be able to walk to a medical tent and have it popped into place, but I lost valuable time in the process, completing Mile 2 in 15:18 when I was shooting for a 7:30 pace.

So let's do some calculations and see what might have happened if I hadn't fallen.

My overall time was 1:50:34 over 13.1 miles. So if we ignore Mile 2, that's a time of 1:35:16 over 12.1 miles. A quick visit to the Cool Running Pace Calculator reveals that to be a 7:52 pace. Not what I was shooting for, but definitely better than an 8:27 pace! If I had run that pace for the entire race, my overall time would have been 1:43:06, or just off my PR of 1:42:55.

Would I have PRed if I hadn't fallen? That's hard to say. Maybe I would have pushed myself too hard at the start of the race and had nothing left for the finish. But I do think if I had been running on an empty course after my fall, I could have made up more time than I did. Thousands of runners passed me while my shoulder was getting treated, and when I rejoined the race, the runners around me were running a much slower pace. I passed hundreds of runners over the final 12 miles of the race. How many?

Given that I was running at an extrapolated pace of 1:43:06, I can look at the results and see how many runners finished between that time and my official time. I finished in the 2,311th spot. If I'd actually run a 1:43:06 I would have finished in 1,222nd. There are some problems with the assumptions made here, but it suggests I probably passed over a thousand half-marathoners -- and that doesn't even count relay runners and marathoners.

But even that number may be low. At the end of Mile 2 my average overall pace was 12:37. Someone running a 12:37 pace would have finished at 9,303rd position in the race. That would suggest I passed nearly 7,000 half-marathoners, because I advanced from a 12:37 pace to an 8:27 pace by the end. That number is probably high, though, because people running slower paces were placed in corrals farther back. Many did not even cross the start line until more than 10 minutes after the gun.

DARTer Josh Schieffer, for example, had a faster net time than I did, 1:49:12 (congrats, Josh!), but he probably hadn't even reached me by the time I left the medical tent -- his net time was more than 12 minutes faster than his gun time, and I only lost about 8 minutes or so getting treated.

So I probably passed somewhat fewer runners than that -- perhaps 3 or 4 thousand half-marathoners. I can't do the same calculation for marathoners, though, because the results page for marathons currently shows the half-marathon results (!). Given that there were about half as many marathoners as half-marathoners, I'm guessing I passed about 5,000 people over 12 miles. That's 417 per mile, or 54 per minute. I may have passed nearly one runner per second. Amazing as that sounds, it actually matches my experience quite well. Remember, I was running on three- and four-lane roads, filled side-to-side with runners. It was like a 12-mile obstacle course. How much did those obstacles slow me down? It's hard to say, but I guarantee you, it's something I'd prefer to experience only once.

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