The benefits of barefoot training really revolve around the intrinsic muscles in the foot being able to go through their full range of motion. When they do that, they get stronger.
Back in about 2001, we were talking to one of our Nike coaches Vin Lananna. He’s been very successful over the years, and so we were asking him: “What is it that really sets your teams apart from other teams? ” and he says: “Toby, we’re actually taking your shoes off.”
Basically, we decide: Okay, we will go on the grass, we’ll bring athletes in, we’ll set up our equipment outside to measure the motion, the joint angles, pressure forces under the foot, barefoot running on grass, and see is this different from running in traditional footwear? So, what we actually found, when we collected our data, was that one of the motion variables was the angle the foot contacted the ground. This was a more neutral angle. The plantar flexion, when they push off, was the full range that you have and the metatarsophalangeal joint, the ball of your foot, had a full range of motion during push off when they went over it. The other thing that we saw was, the toes actually gripped the ground and extended and spread and splayed apart, so those were very different from anything we’ve ever seen in shoe condition.
In a traditional shoe we’re masking and basically holding on to some of that movement and not allowing that to happen and if we want to have a muscle to increase in its strength, it needs to actually go through its full range of motion.
Here’s a solid piece of foam, with just some square lines in it. It’s still a solid piece of foam, and the small intrinsic muscles can not move this. They’re just not strong enough to do that in the foot. But, if I go deeper into this grid line, what we get out of that is a very fluid situation with the same material. It’s now very organic, very easy to articulate.
And this is probably prototype 4. You can actually see, this is my writing on it, where I’m Xing out sipes that aren’t working, that I don’t like. I’m talking about putting in what we call “the reverse flex groove” that allows the toes to both flex or grip and extend, which is something that’s very different about Nike Free from any other type of footwear. The numbers that are on here are actually the depth, in millimeters, of each of those sipes. That was how precise we were when we tried to lay out and engineer this.
Once we did that, it really allowed the foot to be more in control of the shoe, instead the shoe being in control of the foot.
So, we have these numbers for barefoot, let’s take the most built up Nike shoe that existed, which was a 2000 air max, that’s a 10, barefoot is a 0, and it seemed like a good way to approach this, it has an access point. So, we said: We need to create what we call “a 5″, something between that 0 and 10, but then, once we did that, we kind of realized we know what we’re doing and it worked, we could make a 3.0, that would be more barefoot like, right? So, by looking at those variables we were able to say: “Yeah, you’re a 1, a 3, a 5, a 2″, or whatever and that became what I call “the free continuum” or what some people call “the free scale”.
I think the Nike Free really informs everything that we do now to the point where every designer is challenged to think about natural motion in every single design that they’re going forward on.
The fundamental question is: “Why does Nike Free work?” And I think it works because it allows the foot to be the foot.