Super Shoes: Not Everyone Benefits Equally

Controversial results from a recent scientific study (March 2023) of the impact of advanced shoe technologies on running economy and other key metrics

On May 6, 2017, the attention of the whole running world was riveted on the circuit in Monza. Eliud Kipchoge was attempting to become the first person to run 42 km and 195 m in less than 2 hours, albeit without complying with the World Athletics rules required to ratify a world record. He didn’t succeed then, but the final time of 2:00:25 was almost 2.5 minutes better than the world record of the time of 2:02:57. Everyone took notice of the shoes Kipchoge wore, the Nike Zoom Vaporfly Elite, custom designed for this undertaking. The shoe was then released to the general public as the Vaporfly 4%: allegedly, it improved results by 4% – primarily by reducing the energy cost of running (that is, increasing its economy). We can say that a new era began in running: the era of super shoes.

In 2019, Kipchoge finally ran out of 2:00 (1:59:40.2) in a similar out-of-competition race, but already in Vienna. This successful attempt required a number of organizational measures – for example, new asphalt was laid on the race route, and Kipchoge’s manager Jos Hermens said that, compared to Monza, they changed the location of pacemakers and the pace car (to reduce air resistance). The general public’s attention, however, was above all drawn to the new shoes in which the Kenyan ran. It was a new model by Nike called Alphafly, also custom designed for the athlete.

Adding to the buzz around the super shoes were the numerous complaints to World Athletics that shoes of the kind were, in essence, a form of mechanical doping. Eventually, on January 31, 2020, World Athletics issued new guidelines concerning shoes to be allowed in competitions under its own auspices. These guidelines now state that “the sole must be no thicker than 40 mm” and “the shoe must not contain more than one rigid embedded plate or blade (of any material) that runs either the full length or only part of the length of the shoe”.

Whatever the case, all this led to huge commercial success for Nike and forced its competitors to rush to release similar shoes – with thick soles and the obligatory carbon plate – that set super shoes drastically apart from the racing shoes of the past.

Adidas’s Adios Boost 2 in which Dennis Kimetto set the last marathon world record before the Super Shoe Era
Alphafly 2, super shoes from Nike in 2023
Alphafly 2, super shoes from Nike in 2023

Ever since the first Vaporfly went on the market, there has been an ongoing debate in the running world about whether a shoe designed for superstars can be useful for amateurs. In December 2019, the New York Times published a study based on statistics from major races, as well as the Strava service, which stated that such shoes “may give runners an even bigger advantage than we thought”. However, even this did not convince those skeptics who felt, from their own experience, that they did not receive the desired benefits from this expensive equipment. Come March 2023, a study was published in the Sports Medicine journal that backs up such subjective impressions with laboratory measurements followed by systematic review and meta-analysis.

For the first part of the study, a team of scientists from Germany, Spain, and the UK asked seven Kenyan world-class male athletes (able to run a half marathon in under 60 minutes!) and seven European amateur male runners to complete a maximal oxygen uptake assessment and submaximal steady-state running economy trials in three different models of advanced tech footwear (AdvFootTech 1, 2 and 3) and a racing flat (FLAT).

The specific models are not explicitly indicated in the publication; we are only given their specifications, such as weight, sole thickness, and drop. However, the study was conducted at the Adidas Sports Science Research Laboratory in Herzogenaurach, Germany, and, in addition, the brand is easily recognized in the illustrations in this paper, so it is obvious that the models falling under the description should be sought from the manufacturer with the three stripes.

So, the specs of the shoes designated as AdvFootTech 2 (weight 210 g, rearfoot stack height 39.5 mm, forefoot stack height 29.5 mm) definitely match the Adidas Adizero Adios Pro 2. AdvFootTech 3 has similar characteristics, only the drop is not 10 but 8 mm; this could well be the Adidas Adizero Adios Pro 3, but the match of specs in this case is not absolute. However, this is enough to indicate the kind of advanced shoes considered in the study.

Percentage change in steady-state running economy in different shoe conditions for both A world-class and B amateur populations

The treadmill study found that, while modern footwear provided an overall running economy advantage across each group, the pattern varied significantly at the individual level. Paradoxically, the most controversial results were for the Kenyan stars, whose running economy of advanced footwear technology compared to a FLAT ranged from a 11.3% drawback to a 11.4% benefit. As for amateur Europeans, their difference varied from a 9.7% benefit to a 1.1% drawback.

Perplexed, the researchers conducted a systematic review of similar works, of which they found more than 900! Here are the main conclusions of this meta-analysis:

  • There has been identified a statistically significant advantage of modern shoe technologies in terms of running economy.
  • A small effect was detected at very low speeds, a moderate effect at low and medium speeds, and a large effect at high speeds.
  • For world-class runners, the effect was small, while for amateurs, on the contrary, it was very significant.
  • The meta-analysis did not show the statistically significant heterogeneity found within treadmill measurements and mentioned above.

The authors of the work under consideration, in its formal conclusion, still emphasize the individual heterogeneity that they found in their own measurements, admitting that “meta-analysis results reveal an overall significant medium benefit of advanced footwear technology on running economy when compared with traditional flats” and proposing to standardize such studies for better comparison of results.

Commentary by Running Expert

It is striking that in large samples (both the meta-analysis data and the 2019 New York Times publication mentioned early in the text) the advantage of super shoes is obvious, while in small samples the picture is much more inconsistent. From this follows an unambiguous conclusion that such technologies really work, i.e., these are by no means marketing ploys to sell more expensive shoes. The results of studies in small groups may be influenced by statistically insignificant factors.

It’s an entirely different matter, of course, if you take a particular runner whose performance not only gains zero advantage from wearing the super shoes but is, in fact, undermined. Acknowledging their individual issue’s statistical insignificance is hardly a consolation. Now, is there a way to avoid this scenario?

At the very least, remember that shoe efficiency is strongly related to running technique. If a particular model is tailored specifically to forefoot running, it will not work well for a heel-strike runner. Practice shows that, for example, the Vaporfly family is more versatile than the Alphafly – despite their common manufacturer.

To figure out which model is best for you, consult experienced coaches (and not shopfloor assistants). If this is not possible, then you at least take all the time you need to select your shoes in the store – and only do it where you can do trial runs: for example, on a treadmill. When testing shoes, you should check them at different speeds and make sure to include a marathon pace check. Do not focus on subjective feelings exclusively (although they are also very important) but pay attention to your pulse, too; yes, having a heart rate monitor with you when shopping is a must.

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