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Posted: December 18, 2018:  

Athletics: Should Nike’s Zoom Vaporfly 4% be legal?

By Chelsea Ho of Sweat Elite

With the sudden explosion of new PRs in the elite and recreational running stage, Nike’s latest shoe is like none other in the history of distance running

But are we heading down an ugly slippery slope? Here, we discuss the facts and bring to light the hot points of this debate.

Over the last year, an unprecedented number of athletes finished on top of the podium. Out of 36 possible top three finishes in the 2017 World Major Marathons, 19 athletes were wearing Nike’s Zoom Vaporfly 4%. With several records being broken, here are some of the stats for elite runners using these shoes:

  • Eliud Kipchoge recoded the fastest marathon time across all 6 Major Marathons at 2:01:39
  • Shalane Flanagan was the first American woman to win the New York Marathon since 1977 at 2:26:53
  • 8 of the top 12 finishers ran in Nike’s Vaporfly 4% for both the Chicago and New York marathons
  • 5 of the top 6 finishers for the Boston marathon included big names like Geoffrey Kirui, Galen Rupp and Edna Kiplagat


It’s a bold claim: that the Zoom Vaporfly saves up to 4% of energy per stride. That means shaving off around 7 minutes for a 3-hour marathoner, and 10 minutes for a 4-hour marathoner. Astonishingly, the early stats suggest that the company is spot on this time.

The original Zoom Fly came out of Nike’s 2017 ‘Breaking2’ quest to develop the ultimate shoe for breaking the two-hour marathon mark with Eliud Kipchoge, Zersenay Tadese and Lelisa Desisa. The following timeline shows the different shoes in the Zoom series that Nike produced between 2017 and 2018:

  • March 7, 2017: Nike Zoom Vaporfly Elite
  • April 18, 2017: Nike Zoom Vaporfly 4%
  • May 24, 2017: NikeLab Zoom Fly SP
  • June 8, 2017: Nike Zoom Fly & Air Zoom Pegasus 34
  • September 28, 2017: Nike Zoom Fly SP “Chicago”
  • November 2, 2017: Nike x OFF-WHITE Zoom Vaporfly SP
  • April 17, 2018: Nike Zoom VaporFly Elite Flyprint
  • June 1, 2018: Nike x OFF-WHITE Zoom Fly Mercurial Flyknit
  • July 11, 2018: Nike Zoom Pegasus Turbo
  • August 23, 2018: Nike Zoom Fly Flyknit & Vaporfly 4% Flyknit

The shoe giant’s latest Vaporfly 4% Flyknit released in August 2018 gave this shoe a breathable upper to its predecessor.

The shoe’s most controversial features

As identified in Figure 1 (retrieved from Hoogkamer et al., 2018) this Nike shoe has a stiff carbon-fiber plate running from heel to toe, The ZoomX ultralight foam (used in airplane insulation) used in this shoe is highly resilient, compliant and provides the runner with excellent cushioning. The carbon-fiber plate along with the foam is designed to provide an increased bounce at toe-off and allows the heel to sink into the foam minimizing stress on other muscles as well as the ankle and knee joints.

Technically speaking...

Technological advancements in sport are inevitable, so some may view Nike’s new product as an intelligent and unique innovation. However, the question is whether an unfair advantage is being gained from using a ‘spring-like’ contraption within the shoe. Several running enthusiasts believe it is only a matter of time before these shoes are banned in official races. In 2007, the IAAF made springs, a technical aid, illegal in Athletics, in addition to “any other element that provides the user with an advantage over another athlete not using such a device”. While the carbon-fiber plate in the Nike Vaporfly 4% is in itself not a spring, it acts like one when combined with the ZoomX foam providing the user with an advantage over another athlete. Considering this, the use of Nike’s Vaporfly 4% should have been banned in official and major races around the world. However, the interpretation of this rule falls in a gray area and is not entirely illegal as the carbon-fiber plate is not strictly a technical aid. It is clear that there is no real way to regulate these kinds of advances in technology until they actually happen. Banning these shoes would be the equivalent of banning technological advancements that help to create a safer and smarter way of competing in long distance running. However, the other side of the argument finds that technological advancements may take away the human factor and favor the person with the latest and most advanced device, especially when it comes to top athletes.

What’s the anecdotal evidence?

We had a look in some key running forums and here’s what some runners had to say:

Most runners using the Vaporfly 4% find that the shoe does seem to propel you forward when running. Reviewers attribute regularly achieving faster running times to the ultralight weight, extra cushioning and the carbon-fiber plate in the sole of the shoe. Runners with fore-, mid-, and rear-foot striking styles found the shoe provides a slight ‘pop’ with every step during toe-off. The upper Flyknit on the latest model hugs the foot and creates a custom fit, while molding to the foot during a run. Some found the experience of running in different weather conditions to be surprisingly pleasant. During rain, the shoe provided great traction on the wet ground, while the upper Flyknit seemed to be more flexible. Most runners find that this shoe is value for money, especially for those who run on a casual basis but accumulate around 40 miles every week.

A minority of runners reported pain in the gluteus muscles, lower back, knee and ankle joints as well as Achilles tendons after using the Vaporfly 4% shoes. These experiences cannot be dismissed as no study has reported the long-term effects of running in these Nikes. The study by Hoogkamer et al. (2018) derived conclusions of reducing energetic costs by 4% by testing high-caliber athletes over 5 minute trials, at 14, 16, and 18 km/h on a level treadmill. These conditions do not present a very realistic view of the long-term effects the shoe may or may not have on an individual from the general population. A couple of reviewers also noticed that the shoe was slightly fragile in nature and did not hold up after accumulating over 100 miles in them. With a high wear and tear, it suggests that this shoe may not be a financially viable option to longer distance runners who cannot benefit from a sponsor and have to purchase the shoes for themselves.

Conclusion: Key Takeaways

  • Nike’s Vaporflys can increase your running time over as short as 5 miles and over longer distances such as marathons. The claim that it specifically leads to a 4% energy reduction seems reasonably accurate so far.
  • Majority of casual and elite runners report major improvements in their race results.
  • The legality of the shoes is still under question, however they have not been banned yet. Many runners are therefore making the most of the shoes while they are still legal.
  • These shoes are a technologically unique and bring a major advancement in the sport of running.
  • Consider the unusual features of the shoes before purchasing them.


Hoogkamer, W., Kipp, S., Frank, J. H., Farina, E. M., Luo, G., & Kram, R. (2018). A comparison of the energetic cost of running in the marathon racing shoes. Sports Medicine, 48, 1009–1019.

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