"I'm happy to have run two hours for the marathon", added Kipchoge.
The race began in pre-dawn gloom at a brutal pace around the Monza track, which was chosen for its wide, sweeping curves, lack of undulation and cool, low-wind environment.
The spectacle, more science experiment than road race, will involve a clock-carrying Tesla, a rotating cast of big-name pacers and all the engineering and marketing firepower Nike could muster.
It was determined in 1991 by Mayo Clinic anesthesiologist Michael Joyner that the fastest time to run a marathon possible by the human body should come out to 1:57:58.
But Saturday's event is not about the record - in fact, the results nearly certainly won't be eligible for record consideration.
The Olympic marathon champion's incredible demonstration of human endurance will not be officially recognised as a world record because of the carefully controlled (and, as some consider it, controversial) conditions in which the race took place.
The hashtag #Breaking2 is now trending online as marathon fans, who had been glued to the live streams of the event on Twitter and Facebook, heap praise on the runner. Instead, runners completed 17.5 laps around the 2.4km Monza Formula One track.
Nike paid the three runners to forego the London and Berlin Marathons this year prompting some criticism of the event given the resources invested and the fact it will not count as a legitimate record.
"I think we need to accept it as it is". Now it is just 25 seconds.
"I believe in good preparation and planning and if I stick to that the 25 seconds will come".
Besides the favorable track chosen by Nike, the "Breaking2" organizers looked to ideal the athletes' own individual performance, tracking their hydration and nutrition down to the minute details of how much sweat each runner was expected to lose during the race.
It isn't clear what is next for the three runners, who skipped the lucrative spring marathon season to focus on the Nike race.
The three athletes have each been equipped with a specially-designed marathon shoe - lightweight, cushioned, thick soled, and fitted with a metal plate to reduce the amount the foot flexes. The company hasn't said when its sponsored runners will try to set a new record, but its shoes will hit stores later this year. Still, his mark likely won't be ratified as a world record, since Nike didn't obey regulations on pacing and hydrating in its race.
Some of the world's leading scientists were drafted in to offer their expertise, visiting the athletes in their home countries, to monitor their training and share advice on how they can improve their physical and aerobic standards.
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