Nike shoes help elite runners less than thought

An analysis of elite runners’ performances concluded a significant decrease in seasonal best times due to the new footwear technology. Their benefits are yet smaller than previously found.

Kipchoge's Alphafly shoes are forbidden for official competitions — Kipchoge ran a marathon in under 2 hours in an unofficial event with the Alphafly prototype shoes, which are not allowed by the World Athletics | Felix Wong

Nike shoes less beneficial to elite runners than casual runners

Nike shoes revolutionized the world of running in 2017. With their new footwear technology, long-distance runners kept going faster. Although providing real benefits, a new research study led by the World Athletics suggests they are yet smaller for elite runners than previously thought.

The 5 best performances of all time for men’s marathons took place between 2018 and 2019, pushing down the previous world record held by Denis Kimetto from 2014, in 2 hours 2 minutes and 57 seconds, to only the 6^th fastest marathon ever. In 2019, Brigid Kosgei broke Paula Radcliffe’s 16-year-old world record for the women’s marathon.

And the new statistical analysis of elite athlete results in official competitions between 2012 and 2019 reinforces the sensation that Advanced Footwear Technology does improve performances. The results show a significant decrease in seasonal best times in 10-kilometer races, half-marathons, and marathons among the top 20 and top 100 female and male runners. Researchers link these results to the effects of the new AFT.

The shoes reduced race times between 1.7% and 2.3% for elite female athletes. This is a gain of about 2 min and 10 s for the best marathon times. The shoes also improved male marathon performances by 0.6% to 1.5%, and account for an improvement of 1 min and 3 s on average.

It is indeed a significant benefit. However, it is smaller than previously reported.

Nike released the Vaporfly shoes in 2017 claiming runners would be 4% faster with their new technology, which relies on the combination of a thick and light midsole and the embedding of a long and rigid carbon plate. A large-scale data analysis had been conducted in 2018 on regular athletes using a self-declaration data collection method. It showed that the shoes would improve between 3 and 4% the race times of runners in general.

The new results focused on the official competition times during an 8‑year period in 10-kilometer races, half-marathons, and marathons, which gave more insights into the performances of elite runners. And for top long-distance runners, the benefit is less than 3%.

But such help is still a critical advantage among top performers.

No projection of the effect on individual performances

Nike Vaporfly's particular shape — Nike Vaporfly’s particular shape

In 2018, Eliud Kipchoge broke the marathon’s world record time in 2 h 01 min 39 s.

It is 1 min 18 s faster than Kimetto in 2014. Without the 1 min 3 s that the shoes help gain on average, would Kipchoge still have run 15 s faster than Kimetto?

As a consequence, would the world record still be beaten even without the new shoes? Are the shoes really the only factor that marathon records broke in the past years?

According to Dr. Stéphane Bermon, lead author of the analysis and Director of the Health and Science Department at World Athletics (former IAAF), “some athletes benefit from the AFT more than others.” Moreover, “it is difficult and dangerous to extrapolate average figures to an individual situation.”

The projection of results to individual situations could actually lead to opposite conclusions.

Female runner Brigid Kosgei broke Paula Radcliffe’s record by 1 min 21 s during the Chicago marathon. Remarkable progress, yet smaller than the average improvement the shoes provide to women elite runners, according to the analysis. Therefore, would Kosgei not have beaten the world record without her shoes? It would give a different conclusion from what the comparison between Kipchoge and Kimetto’s performances suggests.

In short, the role of the Nike shoes is important in the recent performances but it is not possible to know whether world records would have been broken without them or not.

In fact, some athletes benefit more from the AFT than others and several factors play a role in their performances. For example, it can be seen in the difference between men’s and women’s results from the study. The article pointed out that a lower body mass or smaller shoe sizes could be possible explanations for uneven benefits.

World Athletics adapted its regulation on shoes in 2020, for example with a maximum height for soles, in order to avoid “any unfair assistance or advantage” against the “universality of athletics”. Some shoes already available on the market, such as the Vaporfly that Brigid Kosgei wore in 2019 during her world record, would still be allowed.