Can a marathon be run in under two hours?

— The shoe looked far bigger and more clunky than I expected, a significant design departure from the minimalist and lightweight shoes most marathoners currently wear. To be clear, though, it's not that the shoe necessarily has any extra spring boost, as I learned after dissecting it into its components.

The secret sauce has more to do with a thin carbon fiber plate which sits between two generous pads of foam. This plate serves to keep the foot from bending as much at the metatarsophalangeal (MTP) joints between your toes and your forefoot.

The idea is that runners "bleed" a certain amount of energy the more those joints are flexed, and this plate helps reduce the loss.

Bret Schoolmeester, head of Nike footwear for the global running division, puts a number on how much the shoes can help: 4%.

He says the Zoom Vaporfly Elites improve "running economy" by 4% -- that's the amount of energy required at any particular running speed.

In the lab, lead physiologist Brett Kirby and research director Brad Wilkins put me to the test in a pair of the prototypes the Breaking2 athletes will use in the record-breaking attempt. As soon as I laced up the shoes, I felt myself rocking back and forth. These shoes make you want to move, and I could not stand still.

As I jumped onto the treadmill, I urged Kirby and Wilkins to crank up the speed as quickly as possible, because it was more comfortable to be running than walking. And, looking carefully at slow-motion video of my running gait, I realized the shoes made me more of a mid-foot striker, rather than a fore-foot striker.

It was a different style of running for me, and yet it still felt very natural.

In addition to the shoes, the Breaking2 team has focused a lot on apparel. It is a departure from the usual free-flowing shorts and singlets we're used to seeing on long-distance runners.

To gain as much of a time advantage as possible, the look for Breaking2 is skin-tight, like a sprinter, using materials such as lycra and polyester. On the front of the singlet-style shirt, as well as the mid-thigh shorts, there are small rubbery blades that Steve Jackson, Innovation Project Director, told me urges air along the runner, cutting down friction.

Oxygen, hydration, and time

Besides apparel, there are a few other pillars the Breaking2 team are focused on optimizing.

Overall training is driven by a runner's VO2 max. You probably hear the term a lot -- and simply, it means the maximum amount of oxygen your body can utilize during intense exercise.

V02 is determined by how much blood your heart can pump and how well your muscles can grab oxygen out of the blood stream. While one's VO2 max is, in part, genetically determined, the truth is most never reach their true potential.

Three runners were selected by Nike to help break the record. They are -- Eluid Kipchoge, 32, from Kenya, Lelisa Desisa, 26, from Ethiopia, and Zersenay Tadese, 34, from Eritrea.