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.
13 thoughts on “The 2015 Berlin Marathon: Kipchoge, Symmetricality, and Those Insoles”
I believe your application of the right-hand rule is wrong. You can describe the torque with a torque vector, but that is a naming convention, and not an actual force upwards or downwards. At least, per google and my mechanical engineering training. Now with magnets rotating you can create electro-motive force, but that would be different.
The right hand rule could be relevant here to characterise the spin-angular momentum as in a spinning gyrowheel.
In an ordinary demonstration of a gyrowheel, a wheel is spun in say the XZ plane, a weight is applied to one side, and the wheel spins at a right angle to the pull of the weight, because the angular momentum from the wheel is much larger than the angular momentum from the gravitational pull of the weight. The direction of precession follows the right hand rule.
To see how this might apply to running this model just needs to be rotated. Now the spinning object is the rotation of the upper body carriage in the XY plane during running. The force perturbing the spinning system is not gravitational pull on a weight, but the ground force reaction to the footstrike. Since the torque on the system from the two different foot strikes is similar, but the body is rotating in opposite directions, it seems reasonable to speculate that some sort of precessional force is applying to the body that is the opposite for each foot, and the right hand rule is relevant here.
Eric, if the runner rotates their upper body equally inwards when stepping on their left foot, as when stepping on their right foot — like a mirror image — then any precessional force will be like a mirror image. The right hand rule only gives us a convention for describing the direction of rotation, not to describe any actual force.
Fully agree with Eric: the right hand rule is merely a convention. The only things in physics that I know of to have some predisposition for left or right is the corioliseffect, but that would mean that people on the other side of the equator would have the opposite problem 😉
I think it is more correct to attribute this effect to the asymmetric position of the organs, or asymmetric functioning of the brain…
Yes, exactly. Consider 2 tops (or gyroscopes) spinning in opposite directions. They will move in mirror image to each other.
Thanks very much for clarifying, Steve! Much appreciated.
Bert, I couldn’t say for sure whether people on the other side of the equator have the opposite pattern. 🙂 Enchanting idea. In any case, my main assumption for many years has been that it has to do with the organs and it may even be that people whose livers are more stressed have a stronger version, but I haven’t found it to be that clear-cut. It would be fascinating to see a runner whose organs are reversed (there is such a condition) and see if they have the opposite pattern.
I see. So really there are two (if not more) right hand rules being conflated. In the case of electromagnetic force, the rule describes the direction of the induction of the force. There is an actual force in the thumb direction. But with torque the rule is a convention, describing an angular force by using a quantity normal to it, like using a unit normal to describe a surface. The precession is about the axis, so one describes it using a right-hand rule as a torque through the axis. But with torque, there is no force through the axis.
Very helpful. Many thanks!
As already pointed out, the theory with right hand side rule is not very plausible. Almost everyone is one hand dominant and I believe that similarly almost everyone is one leg dominant. By that I mean that this leg is better for doing actions (like kicking) and in the consequence the second leg is better organized for stabilizing. Also in my case the left leg is more stable. I feel however, that reason for this should be similar to that of why 90% people or so are right-handed. And actually this is not known yet! As Bert already suggested it is believed to be connected especially to the asymmetry of brain itself, but social and environmental factors seem to be important as well. So, this is not an easy question at all!
Leg dominance should be also clearly connected to scoliosis, so one could try to find out if there is a tendency for scoliosis to develop more on one side than the other.
Tomek, leg dominance doesn’t work the way it does with hands. Which attributes would you consider dominant–offering better balance or being free to move through the air? Furthermore, most soccer players kick the ball with the leg they balance on better, not the freer leg, because the pelvis moves with the leg organized for balance and thus more body mass goes into the kick.
In my professional experience there is no relationship between a person’s preferred standing leg and their dominant hand. I see every combination. I’ve been looking at this pattern for many years and have considered a number of possibilities, including that it had something to do with handedness or something to do with driving. Neither of these has stood up to scrutiny. That’s why the right-hand rule as I [mis]understood it seemed like such a neat explanation.
In any case, the pattern is so pervasive it’s unlikely the explanation is only a single thing, such as the liver. Why, after all, is the liver on that side? It’s more likely a number of explanations that all layer over each other. It could be organs and physics and the triple burner meridian (or whichever one it is that runs up the left side and around the head). I will keep looking.
I didn’t mean that leg dominance is correlated directly to hand dominance (so that R-hand implies R-leg or anything like that), only that a reason of choosing one side to be dominant should be similar in the case of leg and in the case of hand. And till know this reason is not known.
I called the leg dominant that is better for more dynamic action like kicking, catching us from falling, starting to ride a bike etc (but this is only a question of convention). So in my case my left leg is better organized for stabilizing.
shows that it is the most typical situation, as for 90% of participants their right leg was dominant (in the sense above), but only for 40% of them it was better for stabilization. So in most of the people dominance of the leg is dependent on the task being performed.
Wow that is unusual. I thought something with torque and did some searching. I don’t have an answer but liked one video explaining torque in a helpful way. I thought maybe it is in part due to your more comfortable side and how you twist. Anyway here is the video I found that interested me around this question. https://youtu.be/M_a3N-SsF60