American Jim Walmsley gave the men's world record set two and a half years ago by Japan's Nao Kazami a serious scare this weekend at the Project Carbon X 2 100 km. A quick look at their splits shows two different race strategies, Kazami essentially going out hard and slowing the second half and Walmsley running the first half more conservatively and then trying to negative split. Both had relatively slow starts before zeroing in on their first half target pace, Kazami settling in around 36:20 per 10 km and Walmsley around 36:50 until they hit halfway. At that point Kazami was projecting a 6:04:10 world record, with Walmsley's 50 km split projecting to a record of 6:08:30.
From there they swapped, Kazami going 36:52 from 50 km to 60 km and Walmsley 36:22. That proved Walmsley's fastest split of the day, as although he stayed close to that pace through 80 km he began to slow for every remaining 10 km split until the finish. In Kazami's case he hit a rough patch between 60 and 70 km, slowing to 37:46 before turning it back around and running faster for each of the next two 10 km splits. The difference in their paces between 60 km and 80 meant Walmsley went ahead of Kazami for the first time at 80 km, at which point he was up 35 seconds, but with the difference in their pace trajectories Walmsley dropped back to just 3 seconds ahead at 90 km.
Kazami had slowed 46 seconds over the final 10 km of his world record, running his slowest split of 37:55. This meant Walmsley had to run 37:57 for his final 10 km to beat Kazami's mark, slower than any of his splits up to that point. That might have seemed doable, but having slowed from 36:33 to 37:41 for his previous two 10 km splits, the latter his slowest of the race, it was a bigger task than in sounded and proved out of range. Walmsley closed in 38:10, like Kazami's closing split his slowest of the race, bringing him in a painful 12 seconds behind Kazami's mark and another second off a new record.
To put in terms of a marathon, Walmsley ran the first half on WR pace, sped up, started to fall off pace coming up to 35 km, and couldn't hold it together in the final 4~5 km. Not exactly a surprise. With a little more conservative early second half he might have been able to hold it together better over the last 20 km, but we'll leave it to the ultra experts to talk about what he might have done differently or might do next time. In any case it was a great effort that came close, and hopefully there's more where that came from.
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