For the attempt to be successful Kipchoge would have to run about 7 seconds faster per mile than current world record holder Dennis Kimetto (who ran 2:02:57 in Berlin in 2014). Although on paper the performance increase of 2.5% required doesn't sound too difficult, but for runners operating at the very limit of human endurance, any gains would be very hard won. Many in the sports science community had predicted that the 2 hour barrier wouldn't be broken for 50 years or more in regular competition. Although Kipchoge ran much faster than the current world record, the Breaking 2 project deliberately employed a number of tactics that meant his time is not recognized as a legitimate world record. I don't want to go into too much detail here, but the Nike team apparently applied a "scientific" approach to optimizing every part of his kit, training, nutrition, and in race tactics.

More Information: mdx.2plm.automation.siemens.com/blog