by Dr John Kelley and Dr Ben Heller
Athletics, or Track and Field, is the poster-sport of the Olympic Games. There are many running disciplines – sprints, middle distance, long distance, track, road, cross country and even hurdles. There’s a steady, if not prolific, grass roots structure for competitive clubs, but perhaps the most likely ways that non-elite sports people will relate to elite running is through parkrun or mass-participation road running events such as the London Marathon.
Whatever their level of running, for most people the most important bit of equipment is the shoe. Common sense suggests that wearing a pair of shoes in good condition and designed for the activity is likely to help reduce the risk of injury, although some evidence suggests that as long as they are well adapted, injury rates are similar for barefoot and shod runners [1]. For runners at any level, consistent, progressive training is the best and most effective way to improve performance and reduce injury risk.
As well as comfort and injury risk, another aspect to consider for the running shoe is the absolute performance difference between shoes in a one-off run. Any shoe design-influenced performance improvements prior to 2016 were small enough not to trigger too much attention and often manufacturers focussed on marketable rather than measurable differences. However, in the 2016 men’s Olympic marathon, the podium (Eliud Kipchoge, Feyisa Lilesa, and Galen Rupp) was filled by athletes wearing a prototype of the Nike Vaporfly shoe. Nike’s new innovation was integral to the Breaking2 project by Nike to support Eliud Kipchoge in his attempts to break the 2-hour barrier for the Marathon. This project was unsuccessful, but resulted in a staggering 2:00:25 time on 6th May, 2017, at the time this was a huge two minute and 32 second improvement on the official marathon record. It was not officially a world record as other factors were non-compliant with IAAA rules such as refuelling, interchangeable pacemakers and pace cars which may have contributed to the performance. Kipchoge was ultimately successful in his sub-2-hour quest during the Ineos 1:59 Challenge, this time wearing prototype Nike Alphafly shoes. His time of 1:59:40.2 remains the fastest ever Marathon, but is not an official world record as the event again did not comply with IAAF (now World Athletics) requirements.
The Nike Vaporfly shoe initiated what The Guardian dubbed in 2023 the Battle of the super shoes [2]. While Nike was the first running shoe manufacturer to produce this type of super shoe, all major manufacturers now how their own equivalent. The recipe is typically a thick, specifically shaped lightweight stack (sole) that incorporates a plate made of carbon fibre or similar material, with the rest of the shoe being as light as possible for the shoe to survive the race distance.
From the start of 2020, all elite athletes, regardless of their sponsor or shoe brand choice, have been wearing some form of super shoe in competition in road races. A similar proliferation has happened on the track, with track spikes incorporating the same technology. Even track spikes specifically designed for sprinters incorporate the technology, adjusted for the different biomechanical requirements of sprinting. The engineering and biomechanical factors behind the way super shoes improve performance will be discussed in another blog article. Here we will focus on the performance achieved in running before, during and after the development and uptake of the super shoe.
The headline-grabbing occurrence in running events are world records. They are very rare – at the time of writing it is over 14 years since Usain Bolt set his 100m and 200m world records. In Figure 1, we can see the number of world record set in running events each year since 2010. During that time, we have the development of super shoes and the COVID 19 pandemic. In 2020, many sporting events were cancelled or postponed, most notably the 2020 Olympics which was held in 2021.
Figure 1. The number of world records set in each calendar year from 2010 to the end of November 2023, according to World Athletics [4]. Mixed road races are included in the women’s records. The period of uptake of the ‘super shoe’ is shown by the blue region. The year most affected by the Covid 19 pandemic was 2020, shown by the yellow region.
Figure 1 shows us that the frequency of a world record breaking performance increases from 1 or 2 a year before the super shoe development to 3 to 5 in 2016 to 2019 to 11 in 2021. We also see a reduction since 2021 back to a still relatively high 5 record breaking performances per year. This is strong evidence that something from 2016 has been improving running performance. If we consider the different race types, sprints (100m, 200m and 400m) are almost not represented with only one record in the whole period considered, the 400m record set by Wayde van Niekerk who was not wearing a sprint version of the super shoe. Middle distance (800m and 1500m) world records are also quite rare, only three set during the time we present, two of which were before the super shoe revolution. Endurance track event (5,000m and 10,000m) world records were rarely broken until 2020, since when we have had 7 world records. The most commonly occurring world records before 2016 were road races, and these increased in frequency between 2017 and 2021. Interestingly the hurdle events (100m hurdles for women, 110m hurdles for men and 400m hurdles) are one of the most frequent records to be broken since 2016. Six out of the 7 records have been in the 400m hurdles.
It seems that there is less of an effect from the super shoe as distances decrease, apart from the 400m hurdles. It is commonly accepted that running efficiency improves with the super shoe, with obvious benefit for long distance running. Running efficiency is likely a less important factor in sprint events as, taken to the extreme, 100m runners are not running out of energy after 10 seconds. However, anecdotal comments by coaches have suggested that stride length is increased when wearing a super sprint shoe. This may be of particular advantage for 400m hurdlers who need to have very specific stride patterns. Performance in the 400m hurdles is in part limited by the minimum number of steps an athlete can take between hurdles. The new shoes may allow athletes to follow a better stride pattern by being able to achieve or maintain a smaller number of steps between hurdles. Even a small increase in stride length may be sufficient to permit one less step, thus it may have a disproportionate effect on speed compared to non-hurdle events.
One thing we are not considering when only examining world records is the inherent talent of the athletes racing year-on-year: sprint events may well be struggling to match the achievements of the generational talent of Usain Bolt. Instead of just world record occurrences, we can consider the best time each year and how it compares to the world record, as shown in Figure 2.
Figure 2. The average best percentage performance for each event type, each year. A year’s best percentage performance is calculated using the average speed of the year’s best performance and the average speed of the world record (as of November 2023). The period of uptake of the ‘super shoe’ is shown by the blue region. The year most affected by the Covid 19 pandemic was 2020, shown by the yellow region.
Figure 2 shows that there was a ‘Covid blip’ for most track events in 2020, likely due to the lack of competitive opportunities. The sprints and middle-distance events seem to have generally marginally improved across the whole period. Endurance, road racing and hurdles show an obvious improvement comparing after to before the development of the super shoe. This confirms that there appears much less improvement for the shorter distances apart from for the hurdles.
The frequency of world records peaked in 2021, with the frequency of world records in 2022 and 2023 being still higher than pre-super shoe. The drop since 2021 may suggest that performance may be reaching a plateau after a step-change improvement. Figure 2 also shows a short plateau in performance since 2021. World Athletics have brought in regulations [5] that limit the height of the shoe stack to 40mm on the road (20mm on the track) and limit the number of rigid structures/plates within the stack to one. This may be limiting continued development of shoe performance.
Figure 2 shows us year-by-year detail for the grouped distances/events. To look at event-by-event detail, we can compare the period of time before the development of the super shoe to the period of time afterwards, using a ratio of times. Figure 3 shows the ratio of the average best performance in a year since the start of 2020 to the pre-2016 average.
Figure 3. The ratio of the mean yearly best performance from 2021-23 to the mean yearly best performance from 2010-2015. Values greater than 1 show that performances in 2021-2023 were better than in 2010-2015. The red circle is around the 400m hurdles events. A logarithmic scale is used on the x-axis.
In Figure 3 we can see that all but two male events show an improvement from the period 2010-2015 to the period 2021-2023. It is immediately obvious that women have had a greater improvement than men across every event. This suggests that women are benefiting more from the super shoe, although there could be other factors at play that are causing a difference between the genders. Perhaps women are physiologically or biomechanically more able to take advantage of the performance benefits than men.
Figure 3 has a logarithmic scale on the x-axis. The straight lines of best fit were included to illustrate the difference between the women and the men, rather than to provide an accurate model of the data. The lines fit the data quite well and it appears that the performance benefit increases in size relative to the race time as the distance increases. This may be related to the fact that running speed negatively scales linearly with the logarithm of the distances, at least at longer distances.
Figure 3 highlights the 400m hurdles as an outlier at the shorter distance for both men and women and we have already discussed the potential reasons for this. It also shows that the 100m and 800m for men are the only events to have a negative performance change. This is particularly true for 800m, which was an event dominated by the current world record holder, David Rudisha, between 2011 and 2016 and retired before the super-shoe was in common use. This may be a case where Rudisha, and the athletes he was closely competing with, were of a higher standard than those running the 800m in 2021-2023. This may also be true in the 100m, where Usain Bolt was dominant up until 2016, although his other event, the 200m, has a positive performance change.
In conclusion, there is strong evidence that the innovation in shoe design has provided a performance boost. Women appear to have benefitted more than men and for both genders the improvement appears to increase in relative magnitude as distances increase. At the shorter distances, the 400m hurdles is an outlier for both genders, showing much greater improvement than races of similar distance. The observed performance benefit may transfer to non-elite runners. Indeed, the benefits appear to be higher at slower speeds, which may mean non-elite runners can gain more performance than elite runners. There is a cost associated with these shoes, typically £200 or more for shoes that are likely to have reduced durability due to their lightweight construction. This seems expensive; however, for comparison, recreational cyclists will often spend considerably more than this to achieve marginal gains from their equipment.
A final note is that we have only considered the super shoe. There are many other factors that could be contributing to the general improvement across all events. As previously mentioned, athlete ability could be a factor, although unlikely to explain the effect across almost all the events. The break for covid could have had a positive effect on the sport, allowing athletes to focus on health, training, and recovery for a year. It could also have had a negative impact on the sport, allowing more opportunity to circumvent drug testing rules. Evidence for both these potential covid effects is sparse at best and the super shoe is at least a much more visible explanation for the observed improvement in performance.
To learn more about our research at the of the Sports Engineering Research Group (SERG) at SHU, please head to either Dr Ben Heller SHU website profile, Dr John Kelley SHU website profile or our website. You can also follow us through our social media channels, available at the top right of this page or through our linktr.
References
[1] Altman AR, Davis IS. Prospective comparison of running injuries between shod and barefoot runners. Br J Sports Med. 2016 Apr;50(8):476-80. doi: 10.1136/bjsports-2014-094482. Epub 2015 Jun 30. PMID: 26130697.
[2] Ingle, Sean. Battle of the super shoes: Nike under threat in London Marathon tech race. The Guardian, 2023. Last accessed December 1, 2023: https://www.theguardian.com/sport/2023/apr/22/brands-try-to-get-a-step-ahead-in-battle-of-super-shoes
[3] Hébert-Losier K, Finlayson SJ, Driller MW, Dubois B, Esculier JF, Beaven CM. Metabolic and performance responses of male runners wearing 3 types of footwear: Nike Vaporfly 4%, Saucony Endorphin racing flats, and their own shoes. Journal of Sport and Health Science. 2022 May 1;11(3):275-84.
[4] World Athletics. Toplists. World Athletics, 2023. Last accessed December 1, 2023: https://worldathletics.org/records/toplists
[5] World Athletics. Book of Rules. World Athletics, 2023. Last accessed December 1, 2023: https://worldathletics.org/about-iaaf/documents/book-of-rules