The super-shoe that could unofficially break the marathon world record: Puma unveils £310 trainer with a double carbon plate 'springboard' - but admits it's NOT race-legal

Puma has unveiled a new 'super–shoe' that could break the marathon world record...but there's a catch. The £310 trainer is not race–legal, meaning any records broken in it would be unofficial. Dubbed the 'FAST–RB NITRO Elite 2', the futuristic shoe features two carbon plates that have been fused together to form a 'springboard'. Puma claims the shoe 'represents the next frontier of running', while acknowledging that it's not race–legal. Romain Girard, VP of Innovation at PUMA said: 'With the FAST–RB 2, we set out to take rule breaking to the next level. 'By simplifying the design and giving our NITROFOAM technology more room to perform, we've created a shoe that delivers the highest energy return we've ever recorded in our testing, within an incredibly lightweight package.' Puma has unveiled a new 'super–shoe' that could break the marathon world record...but there's a catch. The £310 trainer is not race–legal, meaning any records broken in it would be unofficial Dubbed the 'FAST–RB NITRO Elite 2', the futuristic shoe features two carbon plates that have been fused together to form a 'springboard'Puma spent two years crafting the shoe, according to Mr Girard.He explained: 'Two years of innovation, lab testing and collaboration with athletes have gone into refining the experience, bringing together groundbreaking performance and the pure joy of running.' Puma FAST-RB NITRO Elite 2: Key specs Price: £310 Weight: 250g (UK size 8)Colour: PUMA Black-Lime Squeeze Lifespan: 200 miles (320km)Carbon plates: Two fused together into a springboardRoad legal: No Availability: 28 October The shoe has several clever features that are designed to boost speed and efficiency. Puma's 'Nitrofoam Elite' cushioning absorbs energy, stores it briefly, and releases it at precisely the right moment.'It doesn't matter whether you're a heel striker or a forefoot striker,' explained Matthias Hartmann, Head of Material Engineering Innovation Footwear. 'This foam technology offers an improvement for every type of runner.'The top of the shoe is crafted from 'Ultraweave' – Puma's ultra–light weight fabric. Stefano Favaro, Creative Director Teamsport at PUMA, explained: 'Through ULTRAWEAVE, we are able to reduce apparel and kit weight and restrictions to improve performance.'Meanwhile, the outsole is made from 'Pumagrip', which provides improved all–surface tractionWhile many super shoes feature carbon plates, Puma's offering has two, which are fused together to form a distinctive springboard. Puma's 'Nitrofoam Elite' cushioning absorbs energy, stores it briefly, and releases it at precisely the right moment The top of the shoe is crafted from 'Ultraweave' – Puma's ultra–light weight fabric - while the outsole is made from 'Pumagrip', which provides improved all–surface tractionThe idea is that, as you're running, this springboard provides dynamic propulsion, pushing your forwards. Unfortunately, this specific design means the shoe is not race legal, with World Athletics stipulating that shoes can only contain a single carbon plate. The launch will no doubt reignite the debate over super-shoes, and whether or not they give athletes an unfair advantage. The controversy began in 2019, when Kenya's Eliud Kipchoge became the first person to ever run a marathon distance in less than two hours.However, his record was unofficial, because he was wearing the newly developed Nike Alphafly shoes.Described as 'the shoe that broke running', by sports scientist Dr Ross Tucker, Nike claimed that the Alphafly shoe gave a 3.4 per cent increase in speed.Across a marathon distance, that can translate into a difference of two to three minutes and make the difference between a fast race and a world record. The Alphafly's were promptly banned under new guidelines brought into place by World Athletics, but a new generation of shoes soon emerged to skirt these rules. The launch will no doubt reignite the debate over super-shoes, and whether or not they give athletes an unfair advantageWorld Athletics now rules that no shoe can have a midsole that exceeds 40mm in height or contain more than one carbon–fibre plate.As a result, shoe manufacturers have created new, race–legal versions with a 'stack height' that just scrapes beneath the legal limit. For example, earlier this year, Kenya's Sabastian Sawe made history with the first sub–two–hour marathon in race conditions wearing the ADIZERO Adios Pro Evo 3, one of the lightest racing shoes ever created.These shoes feature carbon–fibre plates and 'mattresses' of foam, which allow runners to move faster, while using less energy. But as the technology keeps improving, experts are concerned that super shoes could become a form of 'technological doping'.Speaking to the Daily Mail, Shaun Creighton, an Olympian long–distance runner turned sports lawyer at Moulis Legal, said: 'We should be clear that modern marathon super shoes are performance enhancing devices in a very real sense.'I genuinely do not believe a sub–two–hour marathon would have been achieved without super shoes. 'The regulatory task now is to keep tightening the technical boundaries just enough to preserve the marathon as a contest of human performance first, and of shoe design a distant second.'