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11 January 2021, 8am

Recent changes in shoe technology have led to wholesale revision of distance running records and made comparison with earlier performances meaningless, argues Hugh Jones

Magic shoes

by Hugh Jones

The Nike Vaporfly racing shoe was made available for sale in 2017 to huge fanfare. The manufacturers knew it was a game-changer. They had not only run the tests in their laboratory but had seen what athletes could do when wearing them in open competition.

Shalaya Kipp was a researcher in the study published in 2017 in which athletes wearing the shoes were treadmill-tested and found to improve their running economy by anything from 2–6%. She recalls that “We were calling it ‘The Magic’ because we didn’t have a name for it and whenever we put someone in the shoe in the lab it seemed like a magical result was coming out.”

Eliud Kipchoge was among the very early wearers of the shoe, still only a protoype, when he won gold in the 2016 Olympic Marathon in Rio de Janeiro.

Strange as it might seem it is only relatively recently that different designs of shoe have been rigorously tested to compare their efficiency in action. There were claims decades ago implicit in Reebok’s “Energy Return System” (with promotional material which fancifully included images of springs and kangaroos). But shoes were perceived by athletes and coaches alike as “performance enabling” rather than performance enhancing. The assumption was that models were all very similar and that the most important issues were weight, comfort and injury prevention with what was thought to be a trade-off between the first and last of these: that the lighter the shoe the less support or protection it gave.

That was why Shalaya Kipp, herself an elite runner, was so surprised by the Vaporfly’s test results: energy return seemed to have become a reality. How?

The Vaporfly was noticeably taller than previous models. The Olympic Marathon front runners wearing the protoype in Rio had teetered around a U-turn before the final run-in in a way that drew attention to this. Competition footwear had long been called “racing flats” for a reason. Designers calculated that the higher heel, or what was now termed the “stack height,” would provide both more cushioning and greater energy return. A new, lighter midsole foam combined with a curved carbon fibre plate would assist the forward motion of the foot as it rolls off the ‘stack’, thereby increasing stride length. Or, according to later promotional literature put out after it went on the market, there is “A Built-In Secret Weapon: A full-length carbon-fibre plate underfoot provides a propulsive sensation to help you push the pace.”

The combination of these features on average produced a 4% improvement on running economy compared to Nike’s previous fastest racing flat.

Since the technology was first introduced all the major shoe companies have done treadmill tests with elite athletes. They run at a set speed for a fixed time (maybe 5 minutes) in a range of shoes and measure pulse and lactate levels after each trial. Each company knows how they compare although they are unlikely to publish the results. The general consensus seems to be that Nike have maintained a market lead but the other companies are at various stages of catch-up.

To agents and coaches it might seem a Godsend: put a pair of these shoes on a runner and, without doing anything else, they will improve their performance by about 4%. The shoes do (part of) the work for you. It could be compared to the effect of blood doping: without anything else being done a runner’s current level of performance ratchets up a notch.

Kipp confirms this with a vivid phrase in referring to what was happening in 2016 as “mechanical doping”. Now, “if [a company’s] shoe is not up to standard they will come under pressure from agents, coaches and the athletes themselves to let their contracted athletes run in the Vaporfly or they will be at a disadvantage. We know that the shoe is working well and that it’s creating all the results.”

Results have more recently included Eliud Kipchoge’s “Sub2” Marathon in October 2019, in a paced time trial in which his entire team of pacers were kitted out in the same ‘magic’ shoes. Meanwhile his compatriot Brigid Kosgei broke the 17-year old world record for the women’s Marathon and other word road records also fell at 5km, 10km and Half Marathon.

As on the road so too on the track: while there is not the same test data available the consensus is that the new ‘Dragonfly’ spikes also out-perform all previous models. Conducting a treadmill test is more problematic and the track world records broken in the women’s 5000m and men’s 10000m in October 2020, while likely to have been shoe-aided, could also have been assisted by the ‘Wavelight’ pacing technology.

As the sport’s governing body World Athletics were expected to bring clarity to the confusion and duly obliged with a rule change announced on 31 January 2020. The rule required that the shoe should have a sole that is no thicker than 40mm and contains no more than one rigid embedded plate or blade. It also disallowed the use of prototypes (as in the Rio Olympic Marathon) by specifying that for all competitions held after 30 April 2020 any shoes worn must have been available on the open market for at least four months.

World Athletics President Sebastian Coe said: “we don’t believe we can rule out shoes that have been generally available for a considerable period of time, but we can draw a line by prohibiting the use of shoes that go further than what is currently on the market.”

But the rules only ban the shoes in competitions under World Athletics rules. The ‘Alphafly’ is billed as “A Racing Shoe For the Future of Fast. Best for: Long-distance races… our fastest racing shoe.” That sounds like they are expecting the rules to change again under the relentless pressure in pursuit of ever-faster times.

Like the use of fibreglass poles in the pole vault, mattress landing areas in the high jump, javelin design, and even the change from cinder to all-weather tracks, the ‘magic shoes’ have changed the basis on which performances are evaluated. It was always questionable to compare abilities between athletes of different eras but now it has become so even between athletes of the same era.


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