Gustav Iden’s Kona shoes “legal” according to World Triathlon

Gustav Iden's Kona shoes "legal" according to World Triathlon. (Photo: Livestream)

It was quite a hot item in recent years: carbon running shoes. While we are completely used to carbon plates in running shoes by now, shoe brands keep innovating. Brands keep searching for ways to make athletes run even faster: thicker soles, more responsiveness and carbon. On Running seems to be doing well with their newest model – a prototype of the On Cloudboom Echo 3 – as Gustav Iden just blasted to not only a new course record on Hawaii, but also gold at the Ironman World Championship. But: are these shoes legal? asked World Triathlon about it.

The answer is clear: Yes. After the introduction of carbon plates in running shoes – started by Nike with the Vaporfly – World Athletic came up with a set of rules that brands need to comply with when it comes to running shoes. However, these rules don’t apply in triathlon yet, World Triathlon confirms with That makes Iden’s shoes “legal”. On the contrary, World Athletics – formerly IAAF – would have banned the shoes. That’s because there are rules for how thick the sole can be, how many carbon plates a shoe can have; and, additionally, the shoes need to be made available to the public.

The shoes that Iden ran a 2:36:14-hour marathon on during the Ironman World Championship, have a sole thickness that exceeds 50 millimeters, while World Athletics allows a maximum of 40 millimeters. It could very well be that World Triathlon will go by the rules of World Athletics in the near future, but as recommended by World Athletics that is not the case so far. World Athletics first wants to sort out the rules in more detail. Usually World Triathlon eventually ends up taking rules of the swim-, bike- and athletics world federation into account. However, that’s not the case yet, and that means Iden can enjoy some big soles.