Upright posture

As you likely know, youtube has an annoying "nifty" feature wherein it suggests videos you might like based on previous watched videos. I was watching Tom Kurtz's new Flexibility Express video when it suggested I might be interested in a couple judo videos, including one featuring Tom teaching Judo to a student of his.

For curiosities sake, here's the video, but it's not particularly relevant to my meta-point below

https://www.youtube.com/watch?v=D349Se2aB88

Anyway, as I was watching the video, Kurtz mentions a few times that his student is using his arms to much and that he should remain more upright etc. Of course, that seems like such obvious advice, but I wonder if anyone has casually considered the fuller implications.

For example - if you were to push a car, you'd likely adopt this posture



Now yes, we do see that kind of posture in judo a lot; however, the admonishment to 'stay upright' seems to permeate the ages. Whyfore how come?

I thought it might be fun to have a discussion of the physics (at the level of the laymen, more or less if possible) of upright posture, in terms of power generation, do's and don't etc.

I'll kick this off, then.

Obviously, being more vertical / upright allows for a smaller moment of inertia - meaning that it's easier to turn, pivot etc. The down side is that it requires dynamic stability (movement) rather then static stability to maintain, as the base of support (distance between two feet) is narrow and thus easily perturbed.

This perhaps explains why many judo throws derive power from rotational, rather then pure lifting. In other words, shizenhontai affords easy rotation about an axis, so you may as well use that to power throws.

Other implications?

Creamy creamy baileys wrote:
For example - if you were to push a car, you'd likely adopt this posture



Now yes, we do see that kind of posture in judo a lot; however, the admonishment to 'stay upright' seems to permeate the ages. Whyfore how come?

You push the car like that, but you don't walk up to the car like that, and you don't avoid a car like that ...

and you don't pull a car like that

Can you throw anyone like that? If your butt is that far away it takes too much effort to turn in to a proper throw.

Creamy creamy baileys wrote:
I thought it might be fun to have a discussion of the physics (at the level of the laymen, more or less if possible) of upright posture, in terms of power generation, do's and don't etc.

This is quite an interesting question. I recall from my undergraduate days that the opening chapter of a standard physics text (Halliday Resnick Walker) had a mechanical description of tai-otoshi that never seemed to make much sense - mostly because it required such a high degree of abstraction.

I'm also curious about an analysis of shizentai from a physics point of view.

classical mechanics aside, the picture deals with pushing a car, a car that presumably weighs more than the guy pushing the car. This wouldn't really relate to throwing, but more kuzushi, and even then the position isn't all that relevant since our partners are much more the size of human beings, and not cars (with a few noted exceptions here and there). To pull a door open or push a door closed, my body position stays much more upright - there's no need to assume such an extreme position as it's antithetical to the continued motion of going through the door.

What would seem logical to me is to maintain a position for establishing kuzushi that as closely resembles the position necessary for the kake without going overboard.

And, while we see this type of position in judo competitions, it's more akin to fighting defensively and stalling rather than actually throwing (with a few noted exceptions - I've seen some spectacular uchi matas from the hunched over position, though I think the line going into the throw is a bit different than in a standard, nage no kata type uchi mata).

I'm blathering on at this point, but I do think the point needs to be made - 1. the car is a much different load than a partner or opponent, and requires different leverage. 2. the intent to move the car is not the same as the kake in a throw, but more akin to kuzushi.

The car can't turn and bury you with tai otoshi or grab you by the back of the collar and snap your head down to the mat or hikkikomi gaeshi with you.

Stacey wrote:classical mechanics aside, the picture deals with pushing a car, a car that presumably weighs more than the guy pushing the car.

Of course. The picture does deal with basic mechanics - and particularly, the optimal skeletal configuration needed to push something heavy. The fact that judo happens (or is suppose to) from a more upright posture means that there more to it then just generating the largest back/forward momentum. In fact, even in Sumo - where you can indeed just hoik the other fellow out of the ring - that configuration isn't the only thing happening

Now, considering that one of the major directions of off-balancing is at a 90 degree angle to uke's feet (ie: backwards, basically) - and that we don't / can't shove them into that hole by just pushing, how should this weakness be exploited?

This wouldn't really relate to throwing, but more kuzushi, and even then the position isn't all that relevant since our partners are much more the size of human beings, and not cars (with a few noted exceptions here and there). To pull a door open or push a door closed, my body position stays much more upright - there's no need to assume such an extreme position as it's antithetical to the continued motion of going through the door.

Sure...but what if the door had some substance to it (ie: let's say it weighed 30 lbs or some notional amount). Would that make a difference to how you'd arrange yourself to open / close it?

Firstly, the example of pushing the car fundamentally differs from what happens in judo.

The first difference is that a car is in static equilibrium. A judoka is not. A judoka is in unstable equilibrium.

Secondly, in attempting to explain the physics of judo by referring to the car, one would commit the same mistake as Kanô did, namely to approach the human body as a rigid body, which it is not; a car is though.

The car in itself does not shift its point of gravity, apart from slowly over time because of the fuel in it diminishig. This is even far more critical in airplanes where the center of mass indeed can be greatly affected by burning fuel, which has important effects on its stalling and recovery from unusual attitudes characteristics.

In judo (at least if practising with a partner) one has two bodies in contact which are interacting, what in physics is called a 'collision'. The same applies to the example of the car, but because of the mass of the car is probably about 20 times greater than the mass of the human, the car has a much larger momentum than the person trying to push it. In judo this difference is thus much smaller.

The type of collision is also different. Two judoka interact as a plastic collision, but two cars pushing each other would not be a plastic but inelastic collision. The index of elasticity of the collision between two judoka is described in physics by the coefficient of restitution, i.e. the relative elasticity of their impact.

The human body rotates around 1 of three principal axes (longitudinal, anteroposterior, or transverse), but the car's axes are limited. It does not move up and down or sideways.

Momentum of both a judoka or car to which force is applied changes, the magnitude of tht change depending on how long and how much force is applied.

In the body position one takes to push the car, the shape and surface of your base of support is changed entirely from shizenhontai. Pressure and pressure distribution in the feet are changed. Pressure equals Force over surface area.

The pressure needs to be calculated in order to show the difference between both positions. The surface of the foot depends on the size of the foot, but is often average for a symbolic person about 525 cm² for the foot + 12 cm² for the ball of the foot + 0.0006 m² for the heel, during normal walking. This pressure will be different when in the position indicated for pushing a car. The moments of the forces of the limbs and segments will be thoroughly different and friction will be much greater. The friction force will be determined by the coefficient of the kinetic friction multiplied by normal force. That force will be determined according to Newton's Second or Third Law, that is it will accelerate if unbalanced with F then equally m x a, or it will exert an equal and opposite force on you, thus F = -F. Both gravity and friction forces play a role here.

Through changing hips, ankles and distance between feet we change our stability and instability. In pushing the car we greatly increase our stability in one direction as well as the pushing force. Since the car moves only in one plane, we do not have to care about our own static or dynamic rotational imbalance that could be caused by the opponent like in judo. In judo we do, and the upright position can deal with that through much quicker compensation and changes in body position, essentially "tai-sabaki". In judo, angular momentum becomes very important, but in pushing the car, we have a very linear motion. Hence the optimal body position is different for both activities. In judo the body position has to quickly and dynamically change both depending on what we want to do and on what the opponent is doing to us.

However, historically such positions like in pushing the car where not uncommon in judo. They are clearly jigotai-positions. If you look at the oldest existing original judo exercise (gô-no-kata), you just have to look at the first technique to see its prevalence.



Kanô-shihan clearly and intentionally moved away from jigotai positions in jûdô. As with almost everything in jûdô what we generally attribute to Kanô is not originally his, but was imported. The jigotai position in jûdô interestingly does not originate in one of jûdô's two parent schools (TSYR & Kitô-ryû) but in Sekiguchi-ryû. Kanô has extensively commented and written about the neutral shizenhontai position of Kôdôkan jûdô. Shizenhontai unlike what most Westerners think is not "just standing". Shizen hontai in jûdô in Kanô's mind is a position that has to be learnt. This is quite different from how it is approached in most jûdô clubs. When a novice joins a jûdô club the first things that are taught are how to put on a gi and an obi, closely followed by how to grip and how to make ushiro ukemi. One is usually not really 'taught' at length how to practice shizentai. Instead one is simply told to mimic a neutral position and then a position with the right foot forward. This differs from Kanô's thoughts. I have to think if any of his writings on shizentai exist in translated version. Let me look for this and come back.

Reading and knowing Kanô's philosophical and pedagogical reasons for the choice and reliance on shizenhontai rather than jigotai will not explain the physics, but it is still --so it seems to me-- useful in the context of your question.

In terms of physics, since shizenhontai is far more neutral and dynamic, this position enables you much better to swiftly change your center of mass. The center of mass, as you know, plays a very important role in successfully applying techniques. This is particularly so in lever-based techniques, but somewhat less in mechanical couple-based techniques at least in relationship to effecting the throw though not unimportant in protecting yourself from being countered. Since lever techniques are more difficult to carry out (they require momentary cessation of movement or a "stopping moment" which mechanical couple-based techniques do not) these issues are more critical with regard to this throw. With mechanical couple-based throws it is possible to throw without any 'jûdô' or any kuzushi though obviously the technique in that case does not adhere to the principles of jûdô. Nevertheless, it is precisely this that illustrates why such techniques are less critical when it comes to your own center of mass and thus also your own body's position. From this follows also that the shizenhontai position rather than a jigotai position (or the position you suggest in pushing the car) provides far more advantages with regard to lever-based techniques. If trying to apply lever-based techniques from a jigotai position it will often require having to come back from very far, from too far to be able to make optimal use of debana and swiftly respond to the opponent's actions unless you limit all of your responses to mechanical couple-based techniques or the limited arsenal of of lever-based techniques that still might work from such an extreme position.

Without the hard science and in a way explained very visually and understandably the following clip tackles the weaknesses of such an extreme jigotai position like in pushing the car when applied in budô. The clip doesn't go as far as to apply the problems to actually throwing, but it shows the problems in relationship to actual moving/fighting. It actually compares selected rugby positions with a few classical martial arts principles, espec. tai-sabaki:

Creamy creamy baileys wrote:As you likely know, youtube has an annoying "nifty" feature wherein it suggests videos you might like based on previous watched videos. I was watching Tom Kurtz's new Flexibility Express video when it suggested I might be interested in a couple judo videos, including one featuring Tom teaching Judo to a student of his.

For curiosities sake, here's the video, but it's not particularly relevant to my meta-point below

https://www.youtube.com/watch?v=D349Se2aB88

Anyway, as I was watching the video, Kurtz mentions a few times that his student is using his arms to much and that he should remain more upright etc. Of course, that seems like such obvious advice, but I wonder if anyone has casually considered the fuller implications.

For example - if you were to push a car, you'd likely adopt this posture



Now yes, we do see that kind of posture in judo a lot; however, the admonishment to 'stay upright' seems to permeate the ages. Whyfore how come?

I thought it might be fun to have a discussion of the physics (at the level of the laymen, more or less if possible) of upright posture, in terms of power generation, do's and don't etc.

I cannot effectively and efficiently throw in all directions in any position other than an upright posture. Anyone that can do bent over Judo effectively and efficiently I admire them. I simply do not have the speed and timing from that position.

Creamy creamy baileys wrote:I'll kick this off, then.

Obviously, being more vertical / upright allows for a smaller moment of inertia - meaning that it's easier to turn, pivot etc. The down side is that it requires dynamic stability (movement) rather then static stability to maintain, as the base of support (distance between two feet) is narrow and thus easily perturbed.

This perhaps explains why many judo throws derive power from rotational, rather then pure lifting. In other words, shizenhontai affords easy rotation about an axis, so you may as well use that to power throws.

Other implications?

Shizenhontei is a fundamental building block of judo and other budo. The stance is the most versatile to move from in terms of action-re action.

Now the next part is important. As CK sensei has written there is more to shizenhontai than just standing up straight.

I was taught and also teach to stand with a slight belly forward posture in randori, convex, not concave as is the common. It is unwise to develop a safe feeling by placing ones butt back, take ones head down and stiff arm. Believe it or not it is easier to throw a partner from that posture than throw a partner in an upright posture.

With time and tons of positive experience a judoka can build immense power at the centre of their body, the hara. One learns to 'drop ones weight' Hell, difficult to explain or even teach, it needs to be felt and experienced by fighting a partner who can do this.

When young, before the stone age, I was able at club level to fight pupils without taking hold and they could not throw me? I had zero grip. What one should do is learn to make this convex shape and use the side of the hip to defend. As soon as tori turns in I turn my hip and hit them with my hip making their attack dead before it even starts. My HEAD is up and I could not afford even an inch of allowing my butt to push back or I would sail over the top.

Shizenhontai is also the easiest posture and most effective posture to breath from, deep abdominal breathing just like an opera singer.. Remember the Japanese used to dominate judo because they used their natural hip power whereas in the West we used to try and fight them from the shoulders. The Japanese would love this as they could and did turn in under us to throw. The playing field has levelled somewhat as the Japanese have adopted some Western ideas and we have adopted some of theirs.

It is initially easy to prevent a partner from throwing us by making a concave shape, head down butt back, this is a quick fix that will last for a short time. To stand the chance to master some form of judo it is of vital importance to learn how to stand and move. Only toward the middle of last year did I manage to feel comfortable in walking in judo vis ayumi and tsugi ashi while keeping body control.

The OP asks a very important question, the answer is not so easy to explain without the use of judoka and a tatami.

Mike

I'm gonna simplify things: aside from the initial ability to defend forward throws (I say initial because it doesn't make you hard to throw, it makes you hard to throw safely and as such a noob can adopt this posture and feel like it's useful because his more experienced randori partners don't wanna bury the new guy), I can't think of too many throws that are easier to do from this position than from an initially upright position (I didn't say throws can't be done from there, I said I can't think of throws that are easier to do from there than from upright). and in judo the goal is to throw your partner/opponent, not so much to go full matches without being thrown without accomplishing anything yourself.

also I remembered reading something about how reaction time is faster when one is in a state of equilibrium. I can't help wondering if this comes into play as well.

bent over posture is useful in defense against some attacks (morote gari, etc), but rarely useful for offensive actions.