The sub-2 marathon has become something of a holy grail for the long distance running world; a glowing beacon that brands are striving towards and pushing their athletes to reach.

In this quest, sports brands such as adidas and Nike are developing shoes that they say will help athletes break the two hour barrier.

Seven of the men’s and three of the women’s top 10 fastest marathon times were achieved in the Berlin Marathon over the years, including the current fastest time of 2:02:57. It seems like brands should especially be aiming at this year’s event to set new records.

In last year’s Berlin Marathon, adidas’ Wilson Kipsang was only 10 seconds behind Kenenisa Bekele who won in 2:03:03 (the second fastest men’s marathon time). At this marathon, Kipsang joined Emmanuel Mutai on the 2:03:13 mark (joint fourth fastest marathon time), a time which Mutai also ran at the Berlin Marathon, but two years prior.

The adizero range has already been involved with breaking four world records. Will adidas’ adizero Sub 2 shoe be the next? It certainly did well for Kipsang, who wore it in its premier race earlier this year (the Tokyo Marathon) — he won it with a comfortable two minute lead over the rest of the runners. He didn’t break the 2 hour mark, but he recorded a personal achievement by breaking the sub-2:04 mark for the fourth time in his career.

The prime weapon in adizero SUB 2’s arsenal is its new Boost technology, the Boost Light, which adidas says is lighter than before while retaining the energy return properties.

“Independent sports science research has shown that the new adizero Sub2 can provide 1% improvement in running economy, the overall 100g weight reduction also enables an additional 1% improvement in running economy and its Continental Microweb rubber outsole provides more grip and reduces slip.”

Other features include a lightweight, reinforced mesh upper and its Microfit technology gives support, comfort and good fit.VaporFlyElite_Profile

Nike’s Zoom Vaporfly Elite (above) also works to improve running economy. Its ZoomX midsole cushioning is lightweight, soft and responsive, has a 21mm forefoot stack height, and it is designed to give energy return and protection from the road.

It also has a curved carbon fibre plate, similar to what Oscar Pistorius used on his Nike blades. It “critically serves to add bending stiffness, tuned to improve stride-by-stride efficiency and minimise energy loss over the course of the race.” The extra spring in his step might not have resulted in a win for Pistorius, but Nike is hoping it will propel either Eliud Kipchoge of Kenya, Lelisa Desisa of Ethiopia or Zersenay Tadese of Eritrea to break the 2 hour barrier during a special attempt at the Monza F1 racing track in Italy in May.

It’s this carbon fibre plate and its energy conserving rebound that has sport scientist Ross Tucker questioning the shoe’s legality. He was a vocal critic of the decision to allow Pistorius to run against able-bodied athletes because his carbon spring blades reduced muscle fatigue.

“The elite athletes who have worn [Pistorius’ blades] report that they have no muscle pain after running, which suggests the shoes unload the muscles, exactly as a spring would do,” he writes in an article for The Times.

“Are they legal? That’s the big question. My opinion is that they should not be. I don’t think any device added to the shoe, acting as a spring, or providing energy return, should be legal.

“The current regulation says that the shoe must not be constructed so as to give an athlete any unfair additional assistance, including by the incorporation of any technology which will give the wearer any unfair advantage.

“Curved carbon fibre plates that add to energy recoil, in my opinion, contravene both clauses. They provide additional assistance, and they do so by incorporating a curved carbon fibre plate.

“Where the argument will happen is the definition of unfair, a loophole big enough for a lawyer to run through. Until then, we count down to May, when the attempt is due to take place.”