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World Triathlon Confirms: Iden’s IMWC Shoes Not “Illegal,” No Rules On Running Shoes

Exclusive: An investigation into the legality of Gustav Iden’s prototype Hawaii Ironman run shoes has lead to a surprising conclusion: anything goes. But other than the Norwegians, nobody seems to know.

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Professional triathletes do not have to comply with any rules over their choice of running shoes, World Triathlon has confirmed.

Despite regulation in athletics governing shoe technology – such as limiting the sole thickness – triathlon’s governing body admitted that it isn’t adhering to World Athletics (formerly IAAF) standards and no checks are being made on any of the footwear being worn.

With every other triathlon organization deferring to World Triathlon for guidance on acceptable shoe technology the net effect is that athletes competing in events such as Ironman and World Triathlon’s own races—including its flagship World Triathlon Championship Series—can wear whatever they like when racing.

Unless the situation changes, this also includes the Olympic Games in Paris 2024 and effectively opens a Pandora’s box of opportunity for innovative shoe brands looking to develop faster footwear without restraint.

The issue has come to light after newly-crowned Ironman world champion Gustav Iden of Norway ran a new marathon record at the event’s return to Hawaii on Saturday wearing a pair of prototype ON running shoes that appear to have a chunky midsole (or stack height) in excess of 50mm. World Athletics rules stipulate that the stack height on shoes must be no more than 40mm for road running events.

Gustav Iden at the 2022 Hawaii Ironman World Championships pictured wearing his On prototype racing shoes. (Photo: Brad Kaminski/Triathlete)

RELATED: What the Heck Are On Running Shoes (and Why Should Triathletes Care?)

When not covered by its own rules, World Triathlon has historically adhered to World Athletics regulations for technical aspects such as equipment choice. It operates in a similar fashion for the swim leg (by following FINA) and to a lesser extent the cycling leg (UCI).

However, because World Athletics is currently using a working group to determine the direction the sport should take in terms of footwear development, World Triathlon has abandoned enforcing World Athletics’ rules.

A spokesperson confirmed: “The implementation of the rule that World Athletics has in place, and to which our rules refer to, is still under review by their working group.

“Since the implementation of this rule (the approval process, especially) is still under review and not defined to be implemented in other sports, World Athletics has recommended us not to adopt the rule until the process has been clearly defined. Therefore, currently we don’t check or approve shoes.”

While World Triathlon’s stance ushers in a free-for-all in what triathletes choose to wear, our research found that other than ON and Iden – who have taken advantage of the loophole – no other professionals, coaches or even national federations seem to be aware of the situation and are still attempting to comply with World Athletics standards.

For example, one brand who wished to remain unnamed, decided not to proceed with a prototype tri shoe for a multiple world champion triathlete because its stack height would have breached the 40mm rule.

In contrast, ON, who signed Iden in the week leading into the race on the Big Island, were given a green light to adapt a shoe for the Norwegian any way they pleased.

“Gustav was wearing a Cloudboom Echo 3 model that was adjusted to his specific needs for this race,” said ON’s press officer Silke Tegethof. “To ensure the legality of the shoe, we contacted both the Ironman and World Triathlon organisations who confirmed that they complied with their rules.

“Ironman competitions do not fall under the World Athletics regulations, a fact that both World Triathlon and the Ironman organisation confirmed to us before the event. Ironman rules apply, which do not contain any regulations for running shoes.”

While Tegethof is correct, World Triathlon went further when approached to confirm this wasn’t just the case for Ironman races but extended to ALL types of triathlon.

In contrast, World Athletics has a list of approved shoes it refers to when governing track, field and road races that do comply with its current standards. Shoes such as the Adidas Adizero Prime X with a heel stack of 50mm—for example—are not on the list.

Iden won in his rookie Kona performance with a time of 7:40:24, taking 11 minutes off Jan Frodeno’s course record time from 2019. ON said the exact specifications of Iden’s shoes would not be publicly available.

The focus on high-performance running shoes has increased in recent years following technical improvements using carbon plates combined with highly responsive Pebax foam that purports to increase running efficiency and return more energy to the runner with each stride.

As a result, run times have fallen across almost all distances, with Eliud Kipchoge’s time of 1:59:40 for 26.2 miles in the INEOS: 1:59 Challenge in 2019 capturing global attention as he wore a pair of Nike’s previously unreleased AlphaFlys.

In Saturday’s Ironman World Championship, Iden lowered German Patrick Lange’s marathon course record by more than three minutes to 2:36:14, after swimming 2.4 miles and cycling 112 miles.

The slew of fast times caused an outcry among traditionalists who felt the integrity of athletics, from the track to road, was being eroded as record books were rewritten and certain athletes—such as those wearing and sponsored by Nike—had an unfair advantage. There were also concerns about soaring costs of footwear pricing out runners from taking up the sport or being competitive.

The pressure forced athletics governing body chiefs to bring in regulations to try and rein in shoe development, such as limiting sole thickness and restricting models to just one carbon plate or blade. World Athletics latest regulations came be found here.

Tom Hughes, a Doctorate researcher at Leeds Beckett University in the U.K. and expert in biomechanics explained why increased stack height could provide an advantage to athletes such as Iden.

“In brief, as long as it doesn’t significantly increase weight, it gives more midsole material for return of energy,” he said. “This is the crux of the new style Pebax and other foams. When you have more stack you get more energy.

“It’s a trade off with weight, but these foams are very very light. Secondly, there is an increase in ‘leg length’, which could also confer benefit.”

A 2005 research paper also suggested that increasing leg length may improve running economy by allowing longer stance times and therefore more time to generate force for the subsequent stride.

Whether the loophole will be closed to restore some order to what is permissible footwear in triathlon remains to be seen. World Triathlon said to check with World Athletics for timelines on when its regulations might be ready for adoption.

Triathlete has reached out to World Athletics for comment regarding the conclusion of the working group’s results. Until that time comes, it seems triathletes can wear whatever they like.

RELATED: Understanding Stack Heights in Running Shoes