Those who follow my blog have noticed that I have a great esteem for Ross Tucker, a renowned sports physiologist. Together with his colleague Jonathan Dugas, Tucker had a blog entitled "The Science of Sport". It was active from 2007 to 2013 and then went silent. The last post in the blog was on the sub-2 hour marathon. And the title expressed clearly the authors reservations: "Is the sub-2 hour marathon imminent? Don't hold your breath". Well, it turned out that they were somewhat pessimistic or rather they didn't predict the revolution that would take hold of long distance running in the years to come. And six years after the Science of Sport article, Eliud Kipchoge ran the first sub-2 marathon in history.
In 2013 the men's marathon world record was held by W. Kipsang with 2:03.23. The women's records were established back in 2003 (mixed race) and 2005 (women only) by P. Radcliffe with 2:15:15 and 2:17:42. Today the men's record is held by the late K. Kiptum with 2:00:35 and the women's records are held by R. Chepngetich (mixed race) with 2:09:56 and P. Jepchirchir (women only) with 2:16:16. Just to put the women's records in the right perspective, the men's 2:10 barrier was broken in 1967 by D. Clayton. (At that time no woman had run under 3 hours). And what is happening it's not only due to some exceptional individuals. We are witnessing a real revolution in long distance running. One can argue that what we observe is due to better training and a ripple effect where the performance of the leaders reverberates through the whole runner community. Maybe so. But there is one factor that has undeniably contributed to the explosion of performances: shoes.
But let us start at the beginning. At the end of the 90s the team of the Human Performance Laboratory of the University of Calgary started interesting themselves in the effect of shoe bending stiffness on jump height performance. In order to increase the stiffness they inserted a carbon fibre plate into the shoe midsole.
The initial studies were targeting high jump but subsequent studies extended the subject to that of running economy. It was well known at the time that the energy put in on the metatarsophalangeal joint (the joint between the metatarsals and he toes) is not returned when pushing off. Using shoes with inserted carbon plates reduces the energy dissipated in these joints. The Calgary research showed running energy savings of approximately 1% when using a stiff midsole as compared to a "normal" one. To put the result in perspective (since the energy expenditure for running is proportional to the athlete's velocity) a 1% gain would mean shaving off more than a minute from the time of a marathon for an elite runner.
Curiously the Calgary study did not have any impact on the shoe industry for more than a decade. It was around 2015, when people from the Calgary lab went to work at Nike, that the new shoe generation saw the light. The first modification with respect to the initial design was a bent plate. The reason is that a flat plate makes it actually harder for the calves to push up. The team of the Locomotion Lab at the University of Colorado studied the prototype of the shoes that would become known as the Vaporflys and found that they lowered the energetic cost of running by 4%.
Kipchoge did attempt an under-2 marathon using Vaporflys in 2016 in the Breaking2 event held in Monza. He came tantalisingly close to the 2-hour barrier, completing his run in 2:00:25. While the course design was legitimate (flat course) the remaining conditions (like the use of rotating pacemakers shielding the star runner and the use of a car projecting a laser beam to aid pacing) made that the record could not be homologated.
While the people of the Calgary lab attribute the energy gain to the stiff plate, the Colorado team's opinion is more reserved. For them the metabolic savings of the shoes appear to be due to a superior energy storage in the midsole foam, the clever lever effects of the carbon-fibre plate on the ankle joint mechanics, and the stiffening effects of the plate on the metatarsophalangeal joint. Apparently the midsole foam plays an important role. When the foot hits the ground the sole deforms and some energy is lost. However in today's "supershoes" better foams result in diminished energy loss. (And Nike did further improve upon this by introducing air-filled rubber cushioning).
Following these studies Nike came up with a better model, the Alphafly. Kipchoge used them in Vienna in 2019 at the Ineos 1:59 Challenge and this time the 2-hour barrier did fall. Today Alphaflys are available to anybody who can afford the rather stiff price.
The other brands have caught up with Nike and this explains the explosion of records. World Athletics are trying to put some order in this. They require that shoes be on the market for a month before they can be used in an official competition. Moreover there are limiting the stacking height (the amount of material between the foot and the ground) for track events to 20 mm. However the marathon shoes are allowed to have a 40 mm stack height. Some people are speaking about "shoe doping". I believe that this choice of words is most unfortunate since nobody is cheating and everybody has access to the new shoes. But it remains that they give the athletes a massive advantage.
If you wish to learn more on supershoes, I suggest that you read an excellent article on Runners World.
Speaking of the advantage offered by the shoes reminds me of a controversy going back to the 50s. In 1957 Yuri Stepanov, a soviet high jumper, broke the World Record with a 2.16 m jump. When photos of the record attempt were circulated people noticed that Stepanov was wearing a shoe with a thick sole on his take-off leg.
People cried foul (some were talking about a 4 cm "trampoline" but a closer examination of the photo, as well as other photos of Stepanov in competition, point at a thickness not exceeding 2 cm). In absence of specific rules the IAAF homologated the record and proceeded to limit the shoe sole thickness to 13 mm. This limit has been raised today to 20 mm. (But as P.J. Vazel is pointing out, it is not clear that an elevated shoe offers any advantage in the Fosbury style, it might even present some risk due to the quite different take-off technique). While Stepanov's sole thickness would have been acceptable with today's rules, back in 1957 he was heavily criticised by the media. Being mentally fragile he foundered into depression, alcoholism and committed suicide in 1963, at just 31 years of age.
PS And when we thought we had seen everything, along came the running sandals.
B. Kiplimo won a Marathon in Thailand running with carbon-plated sandals. Now, how can anybody run 42 km with this kind of shoes is a mystery to me. But Kiplimo did it and won the race in a respectable 2:18:55 time.
