Weak shoulder???

[bernard]

Somasimplers,

Here is a try to understand the riddle!
Suppose that is an arm! And suppose there is a constant (for simplification) force that resists to the normal movement.

http://www.somasimple.com/flash_anims/shoulder01.swf

First trial: how is the necessary force to lift up the arm (not represented)?
flash version (http://www.somasimple.com/flash_anims/shoulder01.swf)
html version (http://www.somasimple.com/flash_anims/shoulder01_test.html)

Sorry Takao, but it needs mathematics and physics! :wink:

[Diane]

Bernard, maybe you could move a copy of this to the eye-deas forum?
I like it. However, to perfect it I think you would have to add resistance in there somehow. Maybe from underneath, like a cable that was meant to kick in to stabilize the humeral head down but ends up contracted and pulling the entire periosteum down... (maybe I'm being too concrete and literal and you are being abstract and mathmatical! :))

[bernard]

Ok I move it to Eye-Deas,

But forget cables and...
As a SomaSimpler, I try to explain complex physics with simple images. :wink:

1/ this first step might be more simple (forget the little resistance near humerus head?).
The big arrow shows the weight of the arm itself. it is positioned on the gravity center.

The next steps could show the formation of our chronic problems?

[bernard]

Somasimplers,

I removed the little resistance to show the first major problem.
The arm lever is not linear but varies and thus changes the necessary force to lift up the arm!

Fp* (Lmax*cos((-pi/2)+a)) < (Famax*cos((-pi/2)+a)) *La

http://www.somasimple.com/flash_anims/shoulder02.swf

First trial: how is the necessary force to lift up the arm (not represented)?
flash version (http://www.somasimple.com/flash_anims/shoulder02.swf)
html version (http://www.somasimple.com/flash_anims/shoulder02_test.html)

[Diane]

Hi Bernard,
I'm liking this version better..
I can't help but think it would be more "real", if you showed a force pulling downward on the head of the humerus (latissimus.)
(Sorry, just can't help myself!)
Diane

[bernard]

Diane,

It is an ideal model. It helps to understand the forces happening while we are moving. I think that many of us are totally unable to appreciate the real physic behind a simple movement like lifting up an arm?

But I might be wrong? :wink:

So, I'll try to show, firstly the normal conditions, and the a resistance that breaks a bit the normal motion (call it parasite or SMA, if you want!).

Importance is to touch the reality of physical process to understand the reality of pain!!! :?: :idea:

[bernard]

Somasimplers,

This third essay shows a passive movement. the lift up is applied at the end of the arm (i.e. by a PT).

At the top you see the levers, in action, in black => the passive forces (weight of arm), in green, the level of action for the PT.

http://www.somasimple.com/flash_anims/shoulder03.swf

Third: The necessary force to lift up the arm is applied by a practitioner (passive movement). in green.

flash version (http://www.somasimple.com/flash_anims/shoulder03.swf)
html version (http://www.somasimple.com/flash_anims/shoulder03_test.html)

You can enlarge the view by clicking on flash version!

more to come...

[bernard]

Somasimplers,

This fourth essay shows an active movement. the lift up is applied at the midle top of the arm.
The force is let perpendicular to the lever (not really matter for an essay and does not change the reflection about the idea)

At the top you see the levers, in action, in black => the passive forces (weight of arm), in red, the lever of action for the muscle.

Fp* (Lmax*cos((-pi/2)+a)) < (Famax*cos((-pi/2)+a)) *La

http://www.somasimple.com/flash_anims/shoulder04.swf

Fourth: The necessary force to lift up the arm is applied by the muscle (active movement). in red.

flash version (http://www.somasimple.com/flash_anims/shoulder04.swf)
html version (http://www.somasimple.com/flash_anims/shoulder04_test.html)

You can enlarge the view by clicking on flash version!

more to come...

[bernard]

Hello Somasimplers,

The first conclusions about this simple lift are;
The rules in physics are simple. The moments must be, at least, a bit superior for the active force to produce a movement which is able to lift up the arm.


1/ passive force is applied through a lever which is varying in length during all the movement.
2/ the length of this lever grows first rapidly and then more slowly.
3/ this variation is quite sinusoidal and induce a huge resource at the beginning of the movement.
4/ the active force is the counterpart of the passive one.
5/ the force is applied through a lever which is constant.
6/ the force is then obligatory variant and grows first rapidly and then more slowly.

Some questions about that?

[Diane]

Hi Bernard,
Does this sinusoidal idea you have introduced account for overcoming physical inertia? Or is physical inertia in the body strictly a mental construct, i.e. laziness? (Laziness, languor, torpor, sloth, languidness... "it's a nice long hot June and I don't want to move" sort of attitude..)
:),
Diane

[bernard]

Diane,

No sorry, a simple mathematical fact. Since the beginning of movement (here for the arm) is not easy, a little resistance applied at this starting will produce a huge effect! it will stop/reduce the movement.

Inertia is another thing not introduced for the moment (we try to play simple).

[bernard]

Somasimplers,

This fifth essay shows the same active movement.
But I show only levers and forces for a better comparison.
The right bottom image shows the sinusoidal variation of force/lever.

At the top you see the levers, in action, in black => the passive forces (weight of arm), in red, the lever of action for the muscle.
Middle page shows forces.

http://www.somasimple.com/flash_anims/shoulder05.swf


flash version (http://www.somasimple.com/flash_anims/shoulder05.swf)
html version (http://www.somasimple.com/flash_anims/shoulder05_test.html)

You can enlarge the view by clicking on flash version!

more to come...

[bernard]

Somasimplers,

This sixth essay shows the same active movement but with a little, silly, constant resistance (purple). In reality, this resistance is never constant.

If the muscle is able to lift up the arm, the necessary force is increased in this virstual trial by an amount of 5%. Imagine a daily usage with a muscle obliged to work all time 5% harder! what would be the consequences?

At the top you see the levers, in action, in black => the passive forces (weight of arm), in red, the lever of action for the muscle. Purple is resistance.

Fp*(Lmax*cos((-pi/2)+a)) + Fr*(Lrmax*cos((-pi/2)+a)) < (Famax*cos((-pi/2)+a)) *La [5]


http://www.somasimple.com/flash_anims/shoulder06.swf


flash version (http://www.somasimple.com/flash_anims/shoulder06.swf)
html version (http://www.somasimple.com/flash_anims/shoulder06_test.html)

You can enlarge the view by clicking on flash version!

more to come...

[bernard]

A bit of science, here.

A movement involves a lever and a force to compensate the passive ones.
It is called moments in physics and the equation is like that;

Passive force * length lever = active force * length lever
Fp*Lp = Fa*La [1]

But this equation is equilibrated then no move occurs, so,

Passive force * length lever &lt; active force * length lever
Fp*Lp < Fa*La [2]

We have said that the lever of passive force Lp is not linear and follows a transformation all along the movement.
We can expand it with a mathematical equation where Lmax = the maximum length of the lever.
Lp = Lmax*cos((-pi/2)+a) [3]

Now our equation is;

Fp* (Lmax*cos((-pi/2)+a)) < Fa*La [2]

If the lever of active force is constant then we must conclude that the active force is effectively varying.
Famax = maximum active force to achieve the goal.
Fa = Famax*cos((-pi/2)+a) [4]

The temp equation becomes now;
Fp* (Lmax*cos((-pi/2)+a)) < (Famax*cos((-pi/2)+a)) *La

Of course it can be simplified to the first relation.

[bernard]

If we add a little resistance as in my animation (a constant one for simplification) we have now;

Lr = Lrmax*cos((-pi/2)+a)
Fr = constant resistance

Now our equation is;

Fp*(Lmax*cos((-pi/2)+a)) + Fr*(Lrmax*cos((-pi/2)+a)) < (Famax*cos((-pi/2)+a)) *La [5]

The only way to achieve a movement with the same amplitude is now to increase the necessary force to lift up the arm. But it is sure that resistance is not a constant thing.

[bernard]

The better way to appreciate mathematics and physics is to forget dry formulas and use numbered examples:

The first equation is to remember that lifting up an arm is already a hard thing for a muscle!

Fp* (Lmax*cos((-pi/2)+a)) < (Famax*cos((-pi/2)+a)) *La

This equation could be easily simplified to the form, we take an example when the arm is lifted till the horizontal;

Fp* Lmax < Famax*La

In our visual example, we have Lmax = 2*La. It is quite a real vision.
So,

Fp* 2*La < Famax*La => Famax > 2 Fp

The active force, muscle, is then 2 more times higher than the weight of the arm itself. Fortunately, the active force is applied progressively => protection of joint and efficiency!!!
If our arm is 5Kg then it needs 10kg force for muscle to lift up horizontaly.

[Diane]

Bernard, I must confess I am too dense to follow your logic. Keep going though. It looks like you are creating a mathmatical formula for pain. Maybe after you've perfected it and knocked out any bugs, test driven it, you could explain it to us and we might (I might...) get what it is. (Are you sure you are in the right profession?)
:D
Diane

[bernard]

Diane,

I said it was boring! :oops:
The goal of this topic, in clear, is to give us a mathematical theory that explains how and when we find a weak shoulder. It explains why a patient can't lift the arm and why it hurts him.

Physiotherapy is full of empiric theories or simple findings. Perhaps we need some basic explanations and some visual translations of them?

[bernard]

To help the lost readers, I put some used equations with the animations. I changed also the colors to fit to the appropriate forces and levers.

[Diane]

Yes, the visuals are going to be a big help, as they are already. And the mathmatical formulae will be a big help I'm sure to those who "see" pictures with math. (Not me, I'm sort of math blind.. :( )
Cheers

[bernard]

Somasimplers,

This last essay (for the moment :wink: ) shows that weak shoulders are very common.

The first reason is because the muscles are really weak but in my view this case is rare.

The most common cases are shown here. the muscles are not really weak but the movement is uncomplete???


http://www.somasimple.com/flash_anims/shoulder07.swf


flash version (http://www.somasimple.com/flash_anims/shoulder07.swf)
html version (http://www.somasimple.com/flash_anims/shoulder07_test.html)

You can enlarge the view by clicking on flash version!

Do you understand the subtle differences?

[bernard]

Somasimplers,

Some explanations?

http://www.somasimple.com/flash_anims/shoulder08.swf


flash version (http://www.somasimple.com/flash_anims/shoulder08.swf)
html version (http://www.somasimple.com/flash_anims/shoulder08_test.html)

You can enlarge the view by clicking on flash version!

You have to focus your mind on the spot to understand!!!

[bernard]

Ok,

I give the conclusions.

1/ All movements, faulty or not, have the same origin.
2/ The frontiers between normal movements and faulty ones at the origin are quite thin.
3/ Divergences between faulty and normal appears already near the origin.
4/ Movements have been anticipated before doing really them. We realize them with the good strength, the good speed and the good direction. Brain calculated all parameters with a great accuracy. Only few modifications are done while moving.
5/ At the start of a movement, brain knows already if the movement will be correctly achieved because it has calculated the trajectory and the possible goal.

If brain knows that the movement will inevitably fails, is it really necessary to try it or is it another way to say it?

[bernard]

I must thanks Nari, and Servaas for the paper.

If brain knows that the movement will inevitably fails, is it really necessary to try it or is it another way to say it?

http://www.fibromyalgiasupport.com/library/showarticle.cfm/ID/5845/

[Diane]

This is very intriguing. Nari, you started a thread on this at NOI lately?
I will go back to RE with this info, because in the spring there was a thread there about virtual bodies/phantoms, and I was wondering if the body receiving info and the body putting out actions were having problems overlapping exactly. This article reinforces that line of thought. So thanks Bernard and Nari!

[bernard]

Nari started this one:
http://www.noigroup.com/cgi-bin/ubbcgi/ultimatebb.cgi?ubb=get_topic;f=5;t=000083

[nari]

Servaas kindly responded, but it basically fell on its face.

I wonder why? The concept should involve a radical paradigm shift in management of arthritis - not clear to what- but at least a recognition of the process.

Nari

[bernard]

but it basically fell on its face

I read the topic and I do not see your point of view? Please could you elaborate?

[nari]

Bernard

Nobody replied or responded except Servaas!

Nari

[bernard]

Ah, ok :roll:

[bernard]

Hello,

This is very intriguing.

Not really, muscles are not sensitive by themselve. We know it but our mind refuses yet to accept this fact.

Brain is not sensitive too! And this fact has an enormous impact on body?
A muscular programs that fails by its feedback must be corrected or stopped. If brain corrrects it, well but if the perturbance remains thain brain says failure and creates...pain!