Nike Zoom Vaporfly 4%: Improved performance? Unfair advantage?

Nike Zoom Vaporfly 4%: Improved performance? Unfair advantage?

In a recent Nike funded study, Hoogkamer et al. 2017 concluded that the Nike Zoom Vaporfly 4%, a shoe embedded with a full-length curved carbon fiber plate, reduces the energy cost of marathon running (i.e. improving running efficiency)  by ~4% in comparison to 2 traditional high performing racing shoes (below). The study, then used a predictive model to suggest that a 4% improvement in running efficiency is equivalent to increasing a 2:54/km paced marathon (2:02:58) by 3.4%. To put this 3.4% performance improvement into perspective, let’s undo a 3.4% improvement from recent marathon running performances that were run in the Nike Zoom Vaporfly 4% shoes: Eliud Kipchoge 2:00:25 (Breaking2 at Monza) = 2:04:31 Galen Rupp 2:09:20 (Chicago) = 2:13:43 Edna Kiplagat 2:21:52 (Boston) = 2:26:41 Although none of the above performances were run exactly at 2:54min/km pace (where the 3.4% speed improvement supposedly applies), it can be justified that that improvement would clearly NOT correspond to the predictive models estimation.  Steve Magness of...
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