The trend towards carbon fibre plates in trail running shoes

After years without particularly striking innovations, the appearance of the first trail running shoe model with a carbon fibre plate raises doubts among users. What benefits does it bring? Does it make sense in the mountains? Will it be as noticeable as on tarmac?

Carbon fibre plate has arrived in trail running

Trail running, as a hybrid discipline between traditional running and classic mountaineering, is a perfect blend of the best of two worlds. On the mountain side, you enjoy a natural environment and terrain that often exceeds what we understand as demanding; on the running side, technology and its benefits such as lightness and comfort bring an extra dimension to mountain equipment, traditionally characterised by valuing resistance and durability above all else.

Innovation or technological doping?

In the world of athletics, where success in competitions is an incentive for brands, the concept of "technological doping" has been talked about for some time now to explain those innovations that would be increasing the athlete's capacities in an excessive way and would not correspond to an accepted optimisation of effort in his or her sport.

There are no such debates in the world of mountaineering at the moment. Still far from those innovations that force to regulate even the milimetre of a shoe's cushioning, trail running is nevertheless benefiting from characteristics of shoes for asphalt races that improve the results in competitions.

Hoka One One Mafate Speed 3: 32mm cushioning.

One of those technological innovations that is allowed in athletics with certain limitations is the use of plates inside the midsole, whose benefits in stability and reactivity have proven to be excellent over the years.

Use of carbon plate between the midsole in road shoes. Photo: Saucony.

In trail running they have also been used for a long time in countless models, normally in lightweight and highly responsive materials such as thermopolyurethane (TPU) and the Poliether block amide, better known by its commercial name, Pebax®.

However, despite the common use of carbon plates in high-end running shoes, it was not until now an element that had been used in trail running shoes. It seemed as if the desire to optimise the race and to shave seconds off the time was exclusively for use on tarmac.

To be honest, we must admit that carbon has been used in mountain footwear for a long time, although it is limited to high-end mountaineering or competition ice climbing boots. Of all the characteristics of carbon fibre that we will now go on to detail, it is the rigidity that was most sought after in the construction of the technical mountain boot.

What are the characteristics and performance of carbon fibre?

Carbon fibre is made up of filaments of this chemical element with a thickness that can vary between 10 and 50 microns (one thousandth of a millimetre), less than that of a human hair. Comparatively, carbon is five times stronger than steel, just as strong, and lighter than aluminium.

Exploded view with carbon plate in Flight Vectiv

Its main benefits, apart from this surprising relationship between strength and lightness, are its high flexibility and low thermal expansion, essential attributes for activities carried out in such demanding environments as those in the mountains. The main application of carbon fibre to date has been in the construction of vehicles where energy efficiency is to be maximised: Formula One cars, space navigation, aircraft construction or, more closely related to our world, high-end bicycles.

Application of carbon fibre to mountain equipment

In mountain equipment, apart from the stability plates of high mountain boots that we have already mentioned, carbon fibre has its most outstanding field of action in trail running poles, where its characteristics make it essential in this sport in which every gram less means more energy efficiency. It is also used in ski touring shells, ski boards and certain ice axes and competition helmets, as well as in various safety gear and equipment such as probes.

Leki Micro Trail Pro: carbon fibre in trail running poles

The price of this material, which is still quite high given the complicated manufacturing processes involved in its construction, has not made carbon fibre popular in other elements of our equipment where it would be very useful, such as in the frames of backpacks.

Carbon fibre plates in footwear

As we have said, carbon plates are already used in some models of mountaineering footwear. Boots such as Kailand 6001 GTX or the Millet Everest Summit use carbon fibre insoles with the aim of giving rigidity to the sole without adding much weight and with excellent thermal performance for use at altitude. The extra stiffness provided by full carbon fibre insoles is essential in this high altitude footwear to improve footing with crampons and for safety, to prevent the automatic crampons from popping out if the footwear flexes.

SCARPA Phantom 6000: in mountaineering boots, the carbon plate provides stiffness

In trail running, however, we had to wait until the spring-summer 2021 season to see the first shoe with a carbon fibre plate on the market. The Flight Vectiv de The North Face is a shoe that falls into the Vectiv category, whose main features are a 3D plate, which provides stability and impulse, and a rocker profile that allows for a much smoother transition of the stride.

But what does the carbon plate really contribute to a shoe? Basically, the carbon plate provides reactivity because, when it returns to its original shape after bending during the stride, it generates a forward impulse for the runner. This results in lower energy expenditure and therefore greater running efficiency. But not only that, the plates used in The North Face Vectiv range not only have a spring effect to propel you forward with every stride, but the three-dimensional shape in the heel provides useful stability on steep mountain terrain. Normally TPU stabilisers already fulfilled this mission, the advantage with carbon fibre is the reduction in weight and volume they allow.

The North Face Flight Vectiv, first carbon plate trail running shoe

The spring effect of carbon is well studied on tarmac, but is it really useful for trail running? For now we only have one model on the market with this technology, the Flight Vectiv by The North Face, but the great results in races, personal bests and FKT (Fastest Known Times) seem to mark a trend in which these shoes are always present.

Pau Capell, Ultra Trail Mont Blanc alone using carbon plate. Foto: James Poole, The North Face

In 2020 alone we have had several records in races with carbon shoes, such as Kaytlyn Gerbin's in the Transgrancanaria (also in the Wonderful Trail) or Pau Capell's in the Trail de Menorca Camí de Cavalls to mention just a few of the closest ones.

Will we find ourselves in the near future with a ban or a regulation of technology in mountain races? If we look in the mirror of competitions on tarmac, that may be the fate, although for now the model we have does not seem to contravene any rules such as those that now regulate athletics, neither for cushioning nor for using more than one plate.

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