The biggest story from this morning’s 2015 Berlin Marathon was that Kenyan Eliud Kipchoge won it with the insoles of his trainers hanging halfway out. Here’s a picture.
Talk about an impressive victory.
There are obviously many remarkable things about this feat. Since others have already written about how uncomfortable it was for him, and how remarkable that he pushed through it to run so very fast, I’ll instead do what I do best: obsess about small details and see what can be learned from them.
To my detail-obsessive brain, it was very surprising that both of Kipchoge’s insoles slid out of his shoes to his right. Obviously there was a problem with the shoes, but you’d think it would be a symmetrical problem unless Kipchoge was doing something massively lopsided.
It is a joy to watch Kipchoge run, he has gorgeous form. And he is really remarkably symmetrical, relatively speaking. So, again, why did both insoles slide right?
In fact, if you look closely at the men’s highlights video below, you’ll see that his insoles weren’t the only thing to slide right. His shirt did too.
Both these things are happening because Kipchoge is turning his upper body slightly more to the right while keeping his weight more over the left foot. During the full race it was visible but none of the shots in this short video capture it — this is why I normally wait till the following Sunday to blog about a race, by which time high-quality full-length race video has usually appeared on YouTube.
Nonetheless, here you may be able to catch the fact that his head oscillates a little right of center, and that’s another indicator of the same thing.
This asymmetry, subtle though it seems, means he pushes off both feet not straight forward but slightly towards the left, pushing his insoles the opposite direction, to the right.
Many, many runners have this movement pattern, and in my experience it’s extremely rare to see the opposite. One reason may seem to be the effect of running on a track, turning always to the left, which causes the weight to shift towards the left foot, on the inside of the turn. However the fact that we run counterclockwise on a track is more in response to this phenomenon than a cause of it. The fact that runners much more commonly have their right foot pointed outwards and left foot pointed forward, and that if one foot is larger there’s an 80% chance it’s the left, are also indicators.
Our organs, of course, are not symmetrical. The heart is a bit to the left, while the liver, on the right, is the largest and heaviest organ. The movements of Tai Chi, for instance, are asymmetrical because of such physiological and energetic asymmetries. This all may have something to do with the frequency of the pattern I’m describing.
I have another notion about the cause, however, which might be an organizing factor even for our organs. It has something to do with the rotation of the upper body and the way a gyroscope works. I think it may be the right-hand rule. I’ve been thinking about this for a while in relation to running, and when I ran it by a couple of scientists and they didn’t think I was completely crazy I decided to share it.
It’s probably also not precisely right, and this is where I could use your help if you’ve got a relevant physics/engineering background. Please leave a comment so we can figure this out!
The right-hand rule in physics says that a rotational force creates a force vector one direction only along the axis of rotation. If you make the thumbs-up sign with your right hand, your curled fingers show the direction of rotation and your thumb points the direction of force.
When you run, your upper body turns. When your left foot is on the ground your shoulders are turning clockwise (viewed from above). The right-hand rule says this means there is a downward force when you’re on your left foot.
Whe your right foot is on the ground your upper body is turning left, and the right-hand rule says this creates an upward force.
The upward force when you’re moving over your right foot should make it easier to raise and shift your center of gravity forward and to the left for the next stride. The downward force when you’re moving over your left foot should make it harder to raise and shift your center of gravity to the right. The result is that the weight tends to stay a bit to the left and it’s easier to support yourself in stance on the left and to swing your right leg, twisting in the right side of your waist and turning your shoulders to the right. The extra force also makes your left foot grow larger because bones respond to the force they’re subjected to.
Your upper body turns in walking as well as running, so these forces would affect you even if you’re not a runner.
Okay, it’s way out there. But it’s about as basic a phenomenon as you can find to explain a mysterious asymmetrical movement pattern that many movement and health professionals who deal with runners have remarked upon.
None of this probably matters to Kipchoge, who would have been uncomfortable no matter what direction his insoles migrated. But for the rest of us who might be concerned about how to keep an unavoidably asymmetrical force from generating injury, it’s a powerful reminder of the value of variety, making sure our lives include all different kinds of movement and not just walking and running, so we’re not always subject to the same forces.