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Dorothy
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Hi Dr Deb,

Are you or any other reader familiar with Jean-Claude Racinet's tri-dimensional law?

He has concocted it with an osteopath (?) M. Giniaux, and it relates to the co-ordination of movement in lateral flexion and rotation with flexion / extension.

It describes the movements in a way that does not correspond to my understanding of spinal motion from my training as both a human and animal Chiropractor.

Can you 'unpack' what he is trying to say, and explain it to me??

Thanks

Dorothy

DrDeb
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You will first have to explain to me what you think he is saying, and then we can discuss it. I don't regularly read Racinet. -- Dr. Deb

Dorothy
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Yes,

When discussing the longitudinal flexion of a horse on a circle, or in lateral work, Racinet suggests that if there is lateral flexion associated with spinous process rotation to the outside, this will be associated with spinal hollowing (extension?) and if the lateral flexion is associated with spinous process rotation to the inside this will be associated with spinal lifting (flexion?).

I have 3 questions relating to this:

Firstly, I wonder if he is describing the sum of individual spinal segmental movements, or if he is describing the effects of tilting of the entire ribcage between the shoulder blades?

Secondly, my understanding of the biomechanics of individual spinal joints in the human is that flexion / extension occurs independently of rotation and lateral flexion, whereas rotation and lateral flexion are associated and cannot occur independently of each other. Can you tell me how the horse's spinal joints function and to what extent the individual motions are or are not dependent  on each other?

Thirdly, in certain European Federation Riding Manuals, one is instructed that on a circle, or in lateral movement, the horse should be bent uniformly from poll to tail, even on circles as small as a 6m volte. Is this possible? My understanding is that the degree of rotation and lateral flexion in the equine thoracolumbar spine is so limited that this would not be possible. Please can you clarify the reality for me?

Many thanks,

Dorothy

Obie
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Hi Dorothy,

I am somewhat familiar with this tri-dimensional law from the late Dr. Giniaux. I am an enthusiast of equine osteopath and have not had any special training in it or any other manipulative modality. So I will just say what I think he may be meaning  by the tri-dimensentioal law. I thnik he is talking about one of the main laws that would be associated to any osteopathic manipulating of a horses spine and soft tissue.

Inward bending, outward rotation equals convexity . Inward bending, inward rotation equals concavity . The bending would mean the direction of the bend or arc of the horse, and the rotation would mean the direction of the vertabrae is rotating. I believe you had it the otherway around. If the vertabrae bend in the same direction of the bend of the horse then you would get concavity of the dorsal spine. Basically the "tri" is saying that if you have two of these components then you will have the third. You could have inward bending, concavity then that would mean that the horses vertabrae would be rotating in the same direction of the bend of the horse. If the vertabrae rotate the opposite direction of the bend of the horse then you will always get convexity of the dorsal spine. (which is good) The way I understand in his book is that the ribs themselves tend to bulge slightly inwards with relation to the bend of the horse,and the dorsal part of the spinous process will rotate outward. The vertabrae rotate around an imaginary longitudinal axis which is seperate from the ribs. We can apply this theory with our riding of the horse, and basically this is what Dr Deb has been teaching us.

This is what I understand it to be.

Linda

.

Dorothy
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Hi Obie,

Thank-you for your thoughts, but I still have questions about what this actually means in terms of segmental spinal joint motion.

This implies that spinal bending can occur with rotation in either direction (compared with the human, where lateral flexion is always associated with rotation in one or other direction, depending on the region of the spine)

Is 'spinal bending' the same as lateral flexion?

Does 'inward rotation' or 'outward rotation' mean a tilting or rotation of the entire ribcage between the shoulder blades, or rotation of specific vertebral joints?

By 'concavity' and 'convexity' do you mean spinal extension and flexion?

Are spinal flexion and extension not totally independent of rotation and lateral flexion?

Maybe I am trying to make things too complicated, but it is important to me to understand exactly what Racinet's / Giniaux'  terminology actually means.

Dorothy

 

DrDeb
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Obie, another thanks from me for your post; you have it fairly clear. But Dorothy, we are all suffering from the poor translation of Giniaux's work, and it is this and not what the good doctor actually said or meant that is the source of the problem.

That, and the complete unfamiliarity of most people with the actual bones of a horse's spine. Very few people have ever had the opportunity to examine, much less manipulate, these bones. Another reason why I never can understand why committed riders do not sign up in droves for the anatomy classes, and specifically the "skeleton class" that I offer. Nothing short of your actual, direct experience with the bones will really do.

A description here must suffice, then.

1. When the horse tracks a circle to the right, his body is concave on the right side and convex on the outside. This means his body as a whole, his ribcage, and the chain of vertebrae. And vice-versa if he tracks a circle to the left (an anti-clockwise circle).

2. When the horse tracks a circle to the right, the chain of vertebrae curve as above described. This has no DIRECT effect upon causing him to either raise or lower the spinal chain. By 'raise or lower' I mean either to arch his back or hollow it. By 'direct' I mean that raising or lowering the spinal chain does not automatically happen because the spine has flexed laterally.

3. There is, however, a very powerful INDIRECT effect of lateral flexion, which occurs because the long muscles of the body are affected asymmetrically by lateral flexion. When the horse tracks a circle to the right, the muscles of the right side of the body necessarily function differently, and give different feedback to the brain, than those of the left side of the body. This asymmetry is one of the two keys to the technique which Baucher called 'jaw flexions' and which I call 'head twirling', and also to 'untracking' of the inside hind leg. The asymmetry of muscle function is automatic, a direct and unavoidable consequence of lateral flexion, and the indirect effect that it tends to produce is RELEASE of excess muscle activity, i.e. the release of what a rider would commonly call 'tension' or 'stiffness'.

4. It is utterly impossible for the dorsal process of any vertebra to rotate independent of the rotation of the vertebra as a whole. This is because the dorsal processes do not hinge on to the vertebral centra, but rather both are one single solid bone. Neither do the dorsal processes, considered as a chain, rotate as an automatic consequence of lateral flexion. By 'the dorsal processes considered as a chain rotating', I mean that one may observe, if the chain of lumbar and thoracic vertebrae from a horse are held in the hands, that if the chain as a whole is laid on a tabletop and then flexed to left or right, the tops of the dorsal processes do NOT tilt to either side.

However, in the living horse the lumbar-thoracic chain is not resting, or functioning, on a tabletop, nor is it working in isolation from other body parts. Most importantly, the lumbar chain is attached directly to the sacrum, which in turn is attached to the pelvis, and this again to the hind limbs. And, as Francois Robichon de la Gueriniere taught long ago, there are certain important and beneficial effects when the horse 'untracks', or steps under the body-shadow with the inside hind leg. This action, which Gueriniere himself called 'engagement of the hindquarter' -- (note the vast difference between this connotation and that of Podhajsky or the Germans) -- is the basis and heart of the shoulder-in.

When the horse steps under the body-shadow with the inside hind leg, two things automatically occur: 1. The pelvis, sacrum, and lumbar vertebrae rotate inward, i.e. to the concave side of the bend. By 'rotate' I mean that these parts, as wholes (not just the dorsal processes) rotate around an axis which passes through the centrum of each vertebra from front to back. 2. The lumbo-thoracic chain flexes laterally so that the concave side is on the same side as the hind leg that did the under-stepping, i.e. if the horse understepped with the right hind leg then the spine will curve to the right. Thus, the REAL way to initiate a turn is not by the hands on the reins, but rather by inducing the horse to untrack, i.e. by influencing the horse's inside hind leg. This is the most important maneuver that any horseman can ever understand, because it is not only the ultimate physical key not only to release and to flexions, but to the physical control of the horse's motions and actions.

For more on this, with what I am happy to call 'refrigerator pictures', please hop over to http://www.eclectichorseman.com and get yourself a subscription to "The Eclectic Horseman", which is just at the point of distributing the issue containing the first installment of my series for them on the anatomy underlying a whole series of the actions which we consider important in horsemanship. The first installment is on head-twirling and the second is on untracking.

By 'refrigerator pictures' I mean illustrations that are so good that you really have to copy them and then hang the copy on the door to your refrigerator, so you see them and think about them every day. -- Dr. Deb

Dorothy
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Thank-you, Dr Deb, that clarifies things for me.

I have a question, though, about the actual degree to which the spine can laterally flex - is it as much as is suggested is necessary for a horse to bend uniformly from poll to tail by the FN guidelines on a 6m volte?

I have read that this amount of 'costal flexion' is an illusion created by the swing of the ribcage together with the results you describe when the horse untracks.

Dorothy

Obie
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Dr Deb,

So are the lateral flexions on a longitudinal axis? What flexions are then on a vertical axis? I'm a little fuzzy on this? I think I have the same question as Dorothy. What axis causes the flexion and extention of space between each single vertabrae? I'm not quite sure how to ask this question.

Thanks,

Linda

Dorothy
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Hello Obie,

I understand lateral flexions to be on the longitudinal axis as you suggest, also commonly known as 'bending' or 'costal flexion', such as the bending round a circle or in lateral work.

Flexion and extension in the thoracolumbar spine, by definition, relate to the raising and lowering of the horse's back, so flexion would be loin coiling and rounding up, and extension would be hollowing. In the cervical spine, flexion would be raising the root of the neck and rounding the Mitbah, extension would be stargazing!

Dorothy

DrDeb
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Dorothy, it's perfectly OK to refer to the bending of the horse's spine from side to side as 'lateral flexion'. 'Flexion' just means 'bending'. If you have upward flexion, then two examples of that would be raising the base of the neck and loin coiling. Hollowing the back and stargazing would be two examples of extension -- which is downward bending -- of the spine.

You might note that the reason I use this particular set of terms -- i.e., "lateral flexion", "coiling the loins", "arching the neck", "raising the base of the neck", "hollowing the back", "extending the neck", "extending the nose" -- is because they are clear. The standard medical terminology is, on the other hand, quite confusing and unclear -- "extension" or "flexion" used without qualification, and especially bad are "dorsiflexion" and "ventroflexion", so I avoid using these terms.

The attached illustration is a gift -- it's from the Eclectic Horseman series and you're getting to see it here in a small size ahead of its publication. I can add no more to your query by words, but my belief is that this illustration is paradigmatic and contains the answers you seek. -- Dr. Deb

Attachment: Untracking top view bones labels.jpg (Downloaded 563 times)

Dorothy
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Thank-you, Dr Deb,

That picture explains alot!

I tried to go to the Eclectic Horseman website from your link, and only got a blank page, but I will try again.....

Dorothy

 

Dorothy
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Now this has got me thinking!

Would I be right to think that as the inside hind leg becomes weight bearing and disengages, and the outside hind steps under, it rolls the pelvis together with the lumbar spine to the outside, and will reduce the amount of concavity / convexity in the ribcage?

So, during a stride of this movement with left bend, there is a fluctuating amount of ribcage concavity / convexity as the hind legs cause the pelvis and lumbars to roll from one side to the other.

saffire_100
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The correct address: http://www.eclectic-horseman.com/

DrDeb
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Thanks, Saffire -- seems I am always getting links wrong.

Dorothy -- Please do not use the term 'disengagement' when what you mean is 'untracking'. The term 'disengagement' in this context has been promoted by the Parellioids, and it is both highly (almost laughably) incorrect, as well as confusing. The correct term for the motion being made by the left hind leg in the above illustration is either 'untracking', or else (if you want to use Gueriniere's original term) -- 'engagement of the inside hind leg'. Note, once again, that the old master's connotation is absolutely at odds with the schools of Podhajsky and Otto Lorke (i.e. the term as used by those interested in competitive dressage).

But yes, clearly: a horse cannot go anywhere unless he steps from one leg to the other. How much his arse sashays -- and as a consequence of this, how much the degree of flexion in his spine fluctuates -- will be a product of his build to begin with, and then of how wide he is stepping-in/stepping-out with the hind legs as they alternate.

I attach another gift, from the same upcoming article, which again (having been prepared some months ago), anticipates your question. -- Dr. Deb

 

Attachment: Untracking rear view in and out labels.jpg (Downloaded 533 times)

Dorothy
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Thanks for the link, Saffire, I've got there!

And thank you, Dr Deb, for the excellent diagrammes.

I am not using 'disengagement' in the Parelliod sense, and I do understand the difference and the scope for misinterpretation.

I, too, use the term 'engagement' in the Gueriniere sense, being the equivalent of 'untracking'

If one hind limb is 'untracking' or 'engaging', what word do you use to describe the action of the other? is it 'tracking'? This is the action that I use the term 'disengaging' to mean.

Dorothy

 

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Here is a clip of two mustangs fighting that I have slowed way down so you can see the relations ship between the hind leg and the rib cage.

http://www.youtube.com/watch?v=93Qym4jDrgE

David Genadek

DrDeb
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Dorothy: 'Stepping outward' or 'abduction' would both be good choices for the outward-stepping action of the outside hind leg.

Notice that in all Class I lateral work, that is in all movements belonging to the same class as the Leg Yield, neither the forelimbs nor the hind limbs should ever cross. The inside limb may come as far as the midline, but no farther. Thus the action in this class of movement is always: step out, step in.

Note further that in order to step at all, in any manner, whether protracting or adducting, before the limb that is going to be moved can be moved, the horse must take his weight off of that limb. And to do that, he must lean away from that limb.

Thus, an important insight taught by Ray Hunt, who knew all of this, is this: that the most important part of any lateral work is not to get the horse to step under, but rather, to initiate the movement by actually leaning over the leg that will later step under, so as to free up first of all the leg that needs to step out. The action is to be thought of just as I wrote it above: step out, followed by step in -- not the other way around.

Nuno Oliveira also knew this, and he reveals this knowledge when he says that the most important thing in a half-pass [i.e. in a Class III lateral movement] is not that you should be driving the horse with the leg that is on the side opposite to that in which you want the horse to go, but rather that you should free up and draw the horse toward the side you want him to go. This is why the half-pass so commonly gets 'stuck' -- because either the forelegs, or more commonly the hind legs, can't take the steps they need to take because they're weighted at the wrong time or even all the time. So if you want to go from right to left in half-pass posture, you have to make sure you never get yourself over onto the left side of the horse, and you help him by lifting your left hip when he's standing on his right hind leg, so that in other words you are also "standing" on your right seatbone. This allows him to pick up the left hind leg and get it abducted.

Anatomically, by far the more difficult motion for the horse to make, either with a forelimb or with a hind limb, is abduction. Adduction is easy, and the muscles (pectoral complex and adductor complex respectively) are large, powerful, and have placement that gives them excellent leverage.

Abduction -- the action of stepping out -- is enabled in the hind limb by the femoral biceps -- the 'britches' -- which are fairly capable and which can be conditioned through practice to become even more capable. The real difficulty is with abduction of the forelimb; the muscle that does this in the horse is the deltoideus, assisted by the supraspinatus and infraspinatus. None of these muscles is very big; the deltoideus is actually vestigialized in horses. And none of them have very good leverage for moving the forelimb outward to the side. Therefore, in any class of lateral movement, whether it be Leg Yield (Class I), Shoulder-In (Class II), or Half Pass (Class III), in order to hork that forelimb out there, the horse not only has to be leaning away from it but it also helps if he's collected at least enough to be 'round', so that he's not dead on the forehand. -- Dr. Deb

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Wonderful clip there, David! Thank you very much! What a pleasure! -- Dr. Deb

Dorothy
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Thank you both David and Dr Deb

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DrDeb wrote:

snip:
Nuno Oliveira also knew this, and he reveals this knowledge when he says that the most important thing in a half-pass [i.e. in a Class III lateral movement] is not that you should be driving the horse with the leg that is on the side opposite to that in which you want the horse to go, but rather that you should free up and draw the horse toward the side you want him to go.



Not to take this out of context but how true is it that we strive to "draw" our horses in all that we do way more than "drive" them.  Bringing the birdie along vs chasing it ahead?  The visual of the draw is plain easier for me to follow when sitting astride my horse. That and being in synch with the movement.  Harry helped me so much in getting in time with the horse's feet and not trying to influence them at the least opportune time physically.

Great thread, lots to think on here. Thank you everyone!

Kathy 

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Thanks Deb,

    The thing that caught my eye was how the whole battle seems to be about preventing the inside hip from raising which is the set up for the outside leg to come under. They push the hip down or bite the leg to block the set up.  

     I've attached a picture please explain why the lumbar and thoraciac vertabra all have them paddle thingy's of some sort? Are they to prevent individual rotation, transfer rotation or am I out to lunch here?

David Genadek

Attachment: rotation_prevention.jpg (Downloaded 431 times)

Dorothy
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Dr Deb, please may I answer David's question as I understand it? and then please correct me, this way I will really learn the extent of my understanding. Thank-you for your indulgence!

David, I think that the 'paddle thingys' that you have highlighted are the actual spinal facet joints.

If these did not exist, the only thing that would limit spinal movements would be ligaments, and these would be vulnerable to damage by excessive flexion, extension, rotation or lateral flexion. Without them, the spine would be extremely flexible and unstable, and could not act in the way it does. The facet joints, purely by their bony approximation will significantly restrict the potential for these individual movements, and contribute hugely to the ability of the spine to act as the 'drive shaft' of the hind quarter's engine.

In different species, such as the cat or dog, the facet joints allow for a much greater range of motion thus allowing the cat to curl up as it does.

In humans, the orientation and angulation of the facet joints also ensures a dependency between rotation and lateral flexion, which cannot occur independently of each other, though flexion / extension are independent of R and LF. Hence the expression structure governs function.

Dorothy

DrDeb
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Yes, Dorothy, very good. The proper name of the little paddly-looking things is "accessory articular facets". I have taken David's photo and colored it, which might be helpful to you both. The key to the colors is:

Green -- the smooth "facet" or working face of a lumbar accessory facet. Note that this facet is nearly planar, and oriented nearly vertically. If you consider the lumbar accessory articular facets as a pair -- there is one on the left and the right side of the dorsal process -- you see they have the form of a dovetail joint. This design forbids rotation, inhibits lateral flexion, and promotes loin coiling. As Dorothy notes, the lumbar accessory facets in cats are designed with wide-open oblique angles, hence permitting all kinds of movement and flexibility that simply isn't possible in a horse. Likewise, in a cow the lumbar accessory facets are formed with a cone-in-tube design, which permits lumbar rotation; this is why a bucking bull can kick the cowboy's hat off with a hind hoof.

Rose-red -- David, this photo looks suspiciously like part of that pony skeleton you purchased from the Institute a year ago. That pony had many small bony pathologies, and the red here marks some of them: there is exostosis and rugosity on the outer (non-working) surfaces of many of his lumbar accessory articular processes. These exostoses relate to calcification of the roots of some of the deep intervertebral ligaments and/or the tendons of insertion of the multifidus muscle complex. The pony had a great interest in holding his spine stiff, and/or had systemic arthritis. His teeth tell us he was old. We won't be able to solve why this pony had the pathologies entirely here, but it is important (since most of our readership has never looked at a horse skeleton in any detail) to note that the roughness and irregularity of the articulation marked by the red line is not normal. The WORKING surfaces of the joints are, however, unaffected, so that if the pony needed to loin-coil, he still could -- he would just be stiff in doing it.

Purple -- This marks the working surface of the central intervertebral articular facet. there is one of these (convex) on the posterior aspect of each lumbar vertebral centrum, and one (concave) on the anterior aspect of each. These facets are relatively broad and stout and are shaped more or less like the back or front face of a tablespoon. These are what transmit the back-to-front thrust from the hind legs and pelvis to the thoracics and the rest of the fore part of the body. They permit and promote up-and-down, rotatory, and lateral flexions, so that, as Dorothy notes, it is the lumbar accessory facets rather than these that limit the possibilities for lumbar motion in horses. -- Dr. Deb

Attachment: rotation prevention colored.jpg (Downloaded 423 times)

CarolineTwoPonies
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I have some questions that may or may not fit in this discussion. What exactly happens when we say the horse is "broken" at the third vertebra? Does the c2 and c3 vertebras relate to each other differently or does it just refer to how the silhouette of the neck looks? And what causes vertebras to fuse? I have been trying to understand how horses develop arthritic changes in the neck especially and I read that there can be genetic component, concussion component and training component but I I am looking to better understand how cervical vertebras who are encased into the body so I would think protected can fracture or rub. I just bought a medical book on the equine back but I would like your thoughts doctor Bennett or a link to other materials I can learn from.

DrDeb
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Dear Folks: Here we have an excellent illustration of why I do not recommend most of the German literature.

Whereas the science upon which the postings (now deleted) that were made today by "Digital Goddess" is valid and interesting, the conclusions with regard to "how you are to ride" are not such as I can well recommend.

Neither are the ideas regarding how the cervical muscles 'support' the spine. Those ideas in particular are incorrect and highly damaging.

If anyone wants to go over to Dr. Gerd Heuschmann's website (recommended by "Digital Goddess"), they are welcome to do that, but I will not tolerate the intrusion here of material that is his (and which is copyright to Dr. Heuschmann). The Internet is a wide world, and I invite everyone to make free use of it. However, THIS is my classroom, and in my classroom, we will have discussion by students, not lecture by students.

Digital Goddess, I wonder if I haven't already made your personal acquaintance -- in New Zealand, perhaps? But if not, then, I beg you to introduce yourself by name. You will be able to do that at this point only by EMailing me privately at office@equinestudies.org.

If you care to post anything further, you will kindly do me and everyone else here the courtesy of posing your inquiries in the form of politely-worded questions, rather than in the form of 'well Dr. Deb should really read the existing literature before she pretends to teach.' In other words, DG, I have banned you until you figure out a way to approach this Forum with the attitude of a student.

The idea is, DG, that I am not actually PRETENDING to teach at all. I'm quite familiar with the literature you cite, and if I had not mentioned it previously to Dorothy or to the others here, it might have been for a very good reason. This does not seem to have crossed your mind before you made your series of posts.

So next time, ASK -- that's the way to add to the discussion. What I want to foster here is the exploration of principles -- so that I really never want to hear "this has already been known for a long time."

You see -- I am not really very interested in what you claim someone else has known, or how long they have known it. What I am interested is in how much YOU know and how effective YOU are with horses. We will find out how much that amounts to by the content of your own posts -- in other words, when you stop posting the writings and Web content of other people whom you consider gurus. Let us hear what YOU wonder about, what YOU can draw or photograph, what observations YOU have made, what feels YOU have gotten from horses. Then we will know who you are, and we will know also whether it is really you, and not Dorothy, who requires assistance.

Before you will be allowed to post here again, as I said DG I will require you to EMail me and then you can re-register under your own name. You do not, of course, have to give your address or other personal details. But just as I post under my own name, I ask all serious correspondents here (or those whom I do not already know), to do likewise. If I take the risk of sticking my neck out, then you must do so also. Thanks for the courtesy. -- Dr. Deb

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Hello Dr Deb,

Please may I ask again the question that got sandwiched between Digital Goddess' posts which was, if in the lumbar spine, the accessory articular facets forbid rotation, inhibit lateral flexion and promote loin coiling, how does this change in the thoracic spine? is there some rotation? or even more rotation than lateral flexion?

thank you

Dorothy

 

DrDeb
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Dorothy, no part of the horse's spine is really designed to permit rotation EXCEPT one single joint, and that is the one between the atlas and axis at the front end of the neck. At that joint, rotation is the ONLY motion permitted, and quite a wide arc too.

This is not to say that the horse's spine cannot rotate throughout its length. I have mentioned this before, rather recently, in some other thread or maybe above in this one; I forget where. Anyway, you can see with your own eyes that the spine, considered as a whole chain, can twist to some extent -- for example, look at a horse lying half on its side as they often do when snoozing in sternal recumbency, or in the moment just before they rise from having rolled. Their neck and withers will be vertical and their sternum will be pointing more or less straight downward, but their hips are rolled over about 20 to 30 degrees to one side.

Because the pelvis is joined to the sacrum, and the sacrum to the last lumbar, in such a manner as to prevent rotation at those joints, the rolling over of the hips causes the whole spine up to the base of the neck to twist. It is a twist with a long axis. If you distribute 30 degrees of rotation over the 18 thoracics + 6 lumbars in a normal horse, you get about two degrees of rotation per joint, and this much "looseness" IS designed into the lumbar and thoracic accessory articular joints.

The accessory articular processes of the thoracics are quite different from those of the lumbars. Whereas the facets on the lumbar ones are oriented nearly vertically, the facets on the thoracic ones are oriented nearly horizontally. Both quite effectively inhibit rotation.

However, whereas lateral flexion is absolutely forbidden within the sacrum (because its five vertebral elements are fused together), and forbidden among the sacrum and last three lumbar vertebrae (due to the presence of the inter-transverse articulations), and inhibited among the first three lumbars (due to the lumbar accessory facets) -- it is perfectly OK among any of the thoracics. It is also perfectly OK between the last thoracic and first lumbar, and in fact this joint can act almost as the hinge to the garden gate -- when you are standing to the side of a horse and he wants to kick you, the first thing he does that lets you know you ought to be backing out of there pronto is he'll cock his arse toward you. The 'cocking' is a sidestep he makes with the entire hindquarter, considered from the dock forward to the lumbo-thoracic joint, and hinged upon that joint. The horse who can do a really free half-pass also uses this joint plus any lateral flexibility he can squeeze out of the first three lumbars.

But the thoracics have the greatest lateral flexibility within the freespan of the back. Even the withers, which are inhibited from arching upward or 'fanning' because of the ligamentous ties between the long dorsal processes of those bones, can bend laterally and do so especially in the horse that's had lots of practice at leg-yields and shoulders-in.

One of the things I discuss in the series for The Eclectic Horseman is that the old dressage maxim (like so many dressage maxims) is incorrect -- "the horse should bend evenly on the arc of the circle on which he travels." A horse cannot literally do this -- it's an anatomical impossibility. But there's no need to get into a wrangle over it -- I'm about sick of wrangles, myself -- but this is one of the favorite old areas of argument for dressage enthusiasts, European so-called experts, and railsitters of all stripes. Much more profitable is to look at the horse's spine in detail, just as you keep asking about Dorothy, and I wish more students would do what you are doing. -- Dr. Deb

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Since  the most a horse can roll their hips to the side is 20 to 30 degrees, is that the most that we should ask them to bend? Also does that explain why bending on a circle of 6 yards or less requires two tracking?
Also when riding should we point with our pelvis as part of our setup before the movement, then release everything and hover so to speak so the horse freely moves into the movement?
 Also have thye dates for your fall anatomy class been set yet. And if so can you say how much tuition for the class will be?
 Best wishes
 Bruce Peek

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Dear Bruce: To roll the hips and twist the spine along its long axis is not the same as to bend laterally.

Look again at the top-view skeleton drawing that I posted above. The hips roll as a consequence of the horse stepping under with the inside hind leg. The lateral bend arises not as a consequence of the rolling, but as a consequence of the thickness of the muscular covering of the understepping thigh. When he understeps, there is simply no room for both the rear end of the ribcage and the thigh to be in the same place. The thigh impinges upon the rear end of the ribcage as it steps forward-and-under, and the horse arcs his spine to move the ribcage and make room for the thigh.

What I was saying above is not that "roll" and "flex" cannot, or do not, go together, but that they do not HAVE to go together. Of course, it is easy and natural if when the horse flexes laterally some rotation occurs, and this is what we usually observe in live horses. What the rider feels is that the outside of the ribcage rises, the inside drops; in other words, the platform upon which the rider is sitting tilts. And it does this, along with oscillating up and down, with every step he takes no matter in what gait. It is the combination of tilt, flex, and roll -- complex three dimensional movement -- that gives the walk the typical "butterfly" oscillation that the rider can feel.

As to how you are to sit: Bruce, you've heard me say this before. Just sit. That is how you sit: you just sit. Sit square in the middle of the horse and let the horse do it. Try to draw him rather than shove him. Ride every day with the thought that you are looking for the smallest aid that the horse will respond to with an effort that meets the minimum standard or higher.

As to two-tracking on voltes: not necessarily. Depends on the horse, and also on how you approach the volte. If he is falling in, you bet he'll two-track because it's an escape from being flexible enough longitudinally to track the figure 'square'. So you perfect the volte at a walk and then move to a new goal, which is to perfect it at a trot (or at a pace, in Ollie's case, which by the way he can do). At a canter it will be another matter, however, because you have three choices as to how to approach any volte: as square-away, as a shoulder-in (Class II movement), or as a half-pass (Class III movement). In none of them, however, will you expect the horse to cross any pair of legs.

And Bruce, as to anatomy: you missed it, buddy. The only anatomy class which I offer in the U.S. has, in the past, always been offered in December. We put it off this year to January because I had a truck breakdown and then a freezer breakdown, so that class was held Jan. 4-7th. Next year, I think we will be offering the class in March as being easier for students to get to. So you could think about that.

I have just heard from Dave Elliott, though, and we are going to offer an anatomy up his way March 8-12. To enroll, call Elliott Bit 'n Spur at (403) 687-3000. Don't expect too prompt a reply, as Dave and Louise are headed for Texas this month (snowbirds, yes), but they will get back to you as soon as they can. Thanks for your interest, and hope to see you at one of these classes, as I know you are a very interested student. -- Dr. Deb

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Hello Dr Deb,

thank you, I am much clearer now in my understanding of what is, and can, happen.

However, I have some questions regarding flexion / extension in the spine.

Firstly, when my horse 'lifts his back' when I am riding, how much of this is attributed to actual flexion of the spine (apart from the LS junction), as opposed to the ring of muscles starting to work, loin coiling and lifting at the root of the neck?

Secondly, when I ask my horse to lift his back by touching him under his sternum, the contour of his back changes alot, flattening to a significant degree, again, how much of this is spinal flexion as oppposed to lifting the root of the neck. If the wither thoracics cannot flex, what is happening here?

Thirdly, when an older horse looses the support of the ring of muscles, it will frequently become rather more dipped in the back - is this due to normal extension, or has it become pathological?

Dorothy

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Dorothy, all good questions that, having been asked, will be of help to many other people.

There is no 'opposition' of the Ring of Muscles "vs." upward arching of the spine. The Ring of Muscles is the PARADIGM or conceptual model that explains how upward arching of the spine actually happens. The paradigm allows us to speak of the anatomy in terms of systems, rather than in terms of all the separate parts/separate names (regional anatomy), which is the approach that surgeons need to take.


But a "biomechanic" is a different type of beast. Biomechanics study, particularly of whole-body phenomena such as raising the back under a rider, needs to take a systems-anatomy approach rather than a regional-anatomy approach. Thus, the systems incorporated into the Ring of Muscles paradigm are: the passive support system which is composed of elastic (noncontracting or 'passive') structures that run dorsal to the vertebral chain; the 'core muscles' or active system that are attached below the vertebral chain; and the long perivertebral muscles which are attached above the vertebral chain.

The latter are called 'enemies' and the first two are 'friends'. The major point being made in the papers about the Ring which I have posted at this webite and published in books and in the national magazines is that the German/European teaching 'you must strengthen the muscles of the horse's topline' is wrong, if what you mean by 'strengthen' is to do something (like use draw reins, 'developers', tiedowns, martingales, or certain techniques of saddling or sitting) that directly cause the long perivertebral muscles, the enemies, to contract (especially bilateral contraction, but any excess contraction). These muscles DO NOT raise the back, and their equivalents above the spine in the neck DO NOT arch the neck or support it. There is only one place from which the back may be actively arched, and this is from the contraction of muscles whose attachments to the vertebral chain are below it.

One thing not understood by the Germans and the Germanoids who imitate them -- and this is a historical thing, not just recently; by which I mean, they have never yet understood it -- is how the horse arches his neck. I have seen laughably incorrect expositions of this, written by American veterinarians and published in magazines that, in an earlier day, were the "competition" for Equus Magazine. These wrong explanations fall into two categories: either, like those propounded by Digital Goddess, they think that muscles located above the vertebral chain in the neck somehow 'support' the neck; or else they confuse curling the neck with raising the base. There are indeed fairly large muscles, that span between the basioccipital region of the horse's skull and the ventral surfaces of the first three or four vertebrae, that the horse uses to pull his muzzle backwards for example when he is grazing. He will also use those muscles when he wants to curl the fore part of the neck. But this is not at all the same thing as raising the base of the neck, which is what he does for example on rare occasions when he sees you approaching and he is so glad about it that, like a dog, he first plie-bows and then "stretches" his neck far upward. You notice that this action is an apparent total contradiction to what we know about muscle function! Muscles CAN ONLY CONTRACT and that means they CAN ONLY GET SHORTER FROM END TO END! Right! So then how in the world can the muscles of the neck, given their attachments and their geometry, ever possibly cause the horse's neck to get a foot or more LONGER in length!!?

This was the Great Conundrum of the European Classical High School -- the mystery that all the old authors show us they were working to try to comprehend, all the way from Federico Grisone at the end of the Renaissance to Francois Robichon de la Gueriniere in the 18th century. 300 years, and they still could not totally solve it or even cogently describe it. The first man to put it ALL together was Francois Baucher, whose translation you have just ordered, Dorothy, and which I hope you are enjoying. As I say in the introduction to that, though, neither Baucher nor even his latter-day followers such as DeCarpentry understand in specific how the anatomy works. What they got right was -- as DeCarpentry puts it in the appendix to his book -- "....I am not absolutely sure what is going on with the anatomy, but what I DO know is that when my horse is relating correctly to the bit, his neck is doing THIS" -- and he provides a picture of a horse's neck with seven little blocks drawn in there to represent the vertebrae, and he puts an arrow that shows the blocks moving from the chest upward and forward. Right! And I am only too overjoyed to give these old boys the main credit!

The credit for the anatomy discoveries goes in another direction, and I review this in the 1986 introduction to Vol. I of my "Principles of Conformation Analysis". The main person is the Dutchman Sleijper, who first investigated the axial musculature of whales and dolphins, which, being mammals, also "hump" or "coil their loins" in order to swim, in other words they swim by moving their flukes up and down. He then moved into antelopes and there discovered the differences between swimming animals that hardly have necks and quadrupedal animals that have long necks.

I did no more myself than to read this literature and some related stuff by Kellogg, and realize that something similar must also go on in the horse, an animal that they did not look at. My whole programme of study in this area was kicked off when, one afternoon in 1976, a woman at the stable where I kept Sadie had one of those big old moosey TB geldings that used to be fashionable for dressage before Warmbloods came in. She had trained this horse to piaffe in hand. I asked her to show me, so she put him broadside to a fence and raised the whip and clucked at him, and he quietly "sat" and began trotting in place. I saw him fold the pelvis downward at a sharp angle, but something else also struck me: that at the moment he did this, his body got noticeably shorter -- not just from the downfolding of the pelvis, but in the front end you could see that the distance from the front of the lower part of his throat straight back to, say, his heart or where the girth would go, got less; you could say it got "more compact."

At the same moment, the topline over the LOWER part of his neck rose, and not just because the whole rest of the body was tilted by the lowering of the croup. The neck ROSE FROM THE BASE and in that instant I 'gestalted' and 'comprehended' the whole system. I then went looking in the library at our Museum of Natural History and found the pre-existing literature. It is to academics very important, that even if we obtain an insight which is truly out of our own juices, never to suppose that that would be the first time anyone ever had a similar insight, no matter how outstanding and pleasing it might seem to ourselves. So what Sleijper and Kellogg taught me was that the mechanism for extending the neck, arching the neck, and raising its base is first a product of the canted shapes of the lower three neck vertebrae, and second empowered by the longus colli (assisted by the scaleni), which are located under the declivity at the base of the neck, and which support it as a hammock supports a fat man. When they contract, the fat man rises -- ergo DeCarpentry's little diagram.

Next question. When you touch your horse under the sternum to get him to raise his back, next time have somebody who's a pretty good quickdraw on the camera take sequence photos. Or else have them put it on 'automatic sequence shots' if the camera has that function -- so it goes bzzip bzzip bzzip and you get series of three. Then run them up on your computer and drop the background (or save yourself the trouble by parking the horse in front of a dark wall or a white wall). Then use the overlay function to put no. 2 on top of no. 1 at 75% opacity, then put no. 3 on top of no. 2 at 40% opacity. This will allow you to see what changes are actually occurring.

What you will discover is this: (1) the horse lowers his head, which has an enormous effect in raising the center of his back, via the passive support system (vis. abovementioned). (2) the horse contracts his abdominal muscles, which also raises the center of the back. (3) When the center of the back rises, it must alter the angle of the row of centra which compose the fore part of the thorax. In short, this section of the back tilts downward at a slightly steeper angle than when at rest. Since the dorsal processes are firmly fixed to the tops of these centra, and also because they are long, it looks like the withers are moving up when what they are really doing is tilting just a wee bit forward.

Withers vertebrae that are strongly bound together by the deep ligamentous fibers can "fan" very little. But the strongest binding is between T2 and T6, the vertebrae with the tallest spines. T7-T10 or even as far back as T12 form the BACK aspect of the horse's withers, and these spines are much more capable of fanning. Also, if you have worked with your horse for a long time to supple him and free him, and/or if he is young, a little fanning among all the withers spines is, in fact, possible. The greatest finished horses arch their back, meaning every joint in their back, as much as possible when they bascule or round up or collect. And, you should also remember that the caudal attachment of the longus colli, the major muscle that empowers the raising of the base of the neck, lies under T7 or T8, so the effort does in fact affect the withers. But the whole reason for the existence of the withers is to act as a "stable zone", so that this muscle, and the whole mechanism of the shoulders exteriorly, can have a firm, non-moving place to attach to and from which leverage can be exerted. So no matter how much training or therapy you do, the withers will always be pretty unfannable and pretty stiff.

Third question. When an older horse starts to get a sagging back and you see it accompanied by a sagging belly -- like two ") )" symbols oriented horizontally -- then you know that his core muscles have become unfit. This by itself I would not call pathological: see the upcoming March issue of Equus Magazine (March or April, I'm not quite sure which), where I print a good example of a saggy older QH who is in no wise pathological, and who could be recovered as a good ride if he received some conditioning.

BUT look at this same article for other examples that ARE visibly pathological -- attenuation/strain of the loins, hydrocoeles, sacro-iliac pathologies. In the issue after the one I've just mentioned -- which I am just now finishing -- I'll be printing the photo of a mare whose withers were just beaten to a pulp through her employment as a field hunter but wearing always a saddle with the gullet too low; and another, very weak-fronted mare, with big saddle scars to either side of the withers. These are pathologies that are visible. Sometimes you also get pathologies that are not visible, vis. the ones present on the pony vertebrae submitted in this thread by Dave G., and to detect those you have to see the horse move or try to flex him and find out he can't, etc. Another photo I'll be showing along with the field hunter mare is some anterior thoracics with unreduced, healed fractures of the withers spines. These came from the specimen we dissected in Australia last April: the reason this horse BECAME a dissection specimen was that he was an incorrigible bucker. No wonder!

So the answer to your last question is: it becomes pathological when it becomes pathological. Mere sagging is not pathological. The best technique to determine the borderline between mere sagging and actual 'saddle back', which I would call pathological, is for you to develop (through intimate familiarity with many horse skeletons, and/or study of drawings that I provide, and/or study of the very best skeletal mounts in the world's great Museums of Natural History) -- a sort of "X Ray Vision" that tells you where the row of centra actually are. You need to learn to relate the shape of the topline that you can see and feel with your hand externally to the row of centra internally. This will tell you that the QH with the sagging back is not pathological, though he could easily step over the line in the wrong direction and become that; whereas the busted-withers mare, or the weak-fronted mare, or the mare with the attenuated loins, or the kyphotic mare that I show in these articles are all pathological.

Hope this helps. Cheers -- Dr. Deb

 

 

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Thank you for your time, and thorough answers - they are extremely helpful.

I shall now go and sleep on this information, and see what other questions it throws up.

(I am gradually working my way through other posts, and learning lots!)

Dorothy

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Hello Dr Deb,

Thank you so much for the fridge pictures and the great discussion.  I have a couple of questions relating to this:

If you are initiating a turn (of say 45degrees) by inducing the horse to untrack and this automatically flexes the lumbo-thoracic chain laterally, how much lateral bend would you have in the cervical vertibrae, when the head is twirled?  Would it follow the curve as illustrated in your first drawing?

Secondly, how much lateral bend would you have in a Leg Yield?

I am thinking that in both you would have the bend flowing right through otherwise you would be blocking the movement.  Would trying to keep the neck straight make it difficult for the horse to unweight the shoulder?

Many thanks,

Wendy

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Hi Dr Deb,

I have 2 questions at the moment!

1. How does a pony like the one you mention get the exostoses? I understand that bone will 'grow' in the direction of a consistent pull on it, so it must be due to abnormal tension in the deepest layers of spinal muscles (the multifidus?), so would this occur in a horse or pony that carries itself for a long time with the spine in extension, and the ring unsupportive?

I have recently seen a lovely jumping pony, with a huge heart, and a very poorly fitting saddle, who's back was so locked down, I could not persuade her to coil her loins, flex her spine or lift the root of her neck at all using using any of the 'physical therapy' type lifts and reflexes - would she be a candidate, in time, for this type of arthritic change?

2. Is there a consistent relationship between the position of the vertebral centra and the rib angles, and can I use the rib angles to indicate the positioning of the centra?

Thank You

Dorothy

Sam
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Hi Dr Deb and everyone,

Thanks for the fridge pictures, these are awesome.  Also thanks everyone for the great thread, as usual am learning so much here.  I have about twenty questions but am just off to ask the horse first.  Happy 2010.

Kind Regards Sam.

David Genadek
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     Okay, it seems those little paddle thingies are very important so let me see if I can lay this out from an overall systems perspective.

     Imagine if you will an old-fashioned oscilloscope with the  round screen and in the screen appears horse from the side view. Slowly the body fades away so all that is left is the spine. The spine is a wave shape. Below our screen there are two knobs. One knob controls the hind end of the wave and the other controls the base of the neck. By turning the two knobs you vary the shape of the wave.  This is a two dimensional view. So now let the screen part of the oscilloscope fade away and let the wave rotate around so you're looking at it at from a 45° angle. Now where the sacrum would be add at a stick that goes 90° to the wave. Next add two controls to the bottom part of the oscilloscope these would be  up-and-down sliders which represent the legs of the horse from a three-dimensional perspective. By sliding the two sliders up and down your rotating the entire wave and thus influencing  its direction.

Conclusions:

    Straightness is important because it allows uninhibited spinal rotation. If any of the horses reciprocating systems are out of balance it will inhibit or block spinal rotation.

   Properly initiated gaits are a product of the establishment of a pattern of spinal rotation in conjunction with the setting of oscillatory limits of the spine through engagement of the hind quarter and the lifting of the root of the neck.

   The way you get a horse to bend in the rib cage is through a placement of the hind feet. So for those people who say horses do not bend in the rib cage what they are in fact saying is they have not yet gained governance of the hind legs.

David Genadek

Last edited on Sun Jan 24th, 2010 05:52 pm by David Genadek

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Hello David,

A very interesting perspective!

It would be fascinating to take this model further and examine the difference in the relative movements in walk, trot and canter (and other gaits). I am imagining hard.

Dorothy

 

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David, I'm not quite sure I understand where you're going with this....true enough, when a horse is not straight, it inhibits (or screws up) ALL THREE dimensions of possible oscillation, i.e. up-down, side-side, and rotatory. However, as I mentioned above and as you saw in anatomy class, rotation -- which means motion around the fore-aft spinal axis -- is freely permitted in horses only at the joint between the atlas and axis vertebrae. As I have been saying in this thread, all other rotation that occurs is a kind of twisting, like a barber-pole, along the entire spine, i.e. lumbars + thoracics + lower cervicals. Although a horse's hips might drop over quite a bit (depending how vigorously he's moving, in what manner he's moving, and also on how wide his arse is), all the rotation that he can accomplish by lowering one hip would never be more than 30 degrees at the highest extreme, and normally more like 10 to 15 degrees. Again, as I have mentioned above, this imposes on average less than 2 degrees of rotation upon any one spinal joint outside of that between the atlas and axis.

From this you may reason that rotation is the MINOR component of spinal motion in horses. Further, in the ridden horse, rotation even where it is naturally designed to occur, i.e. between the atlas and axis, is to be as much as possible forbidden by the rider; in other words, the horse is not to be allowed to tilt his nose up to the side. The reason for this is that, if a horse is 'stuck' on other bends that we would like him to make, particularly lateral bends, finding these difficult he will offer to twist his head up to the side instead. Many horses will do this instead of twirl their head properly when asked, head-twirling being pure lateral translation or sideslipping of the occipital condyles upon the atlas, with no rotatory component whatsoever. If the rider or therapist permits anything else, it is not good form and to that degree the therapy will not be effective.

All gaits have their characteristic oscillatory 'emphasis' or 'composition'. The walk presents some up-down, lots of side-side, and lots of rotatory motion. Gait is similar but all the amplitudes are diminuendo (this is why gaited horses are in special need of suppling exercises, for 'diminuendo' can easily degrade into to 'rigid'). The trot presents about equal amounts of up-down and side-side, with less rotatory (and yet to sit the trot, it is crucial that the rider feel and follow the rotatory component; this is the key to sitting without bouncing). The canter, gallop, jumping, and airs above the ground emphasize the up-down oscillation, with less side-side or rotatory.

But even the particular mixture of oscillations at each gait differs from horse to horse, depending not only on build but age, soundness, and whether or not there is a background of proper training. Cheers -- Dr. Deb

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Wendy wrote: Hello Dr Deb,

Thank you so much for the fridge pictures and the great discussion.  I have a couple of questions relating to this:

If you are initiating a turn (of say 45degrees) by inducing the horse to untrack and this automatically flexes the lumbo-thoracic chain laterally, how much lateral bend would you have in the cervical vertibrae, when the head is twirled?  Would it follow the curve as illustrated in your first drawing?

Secondly, how much lateral bend would you have in a Leg Yield?

I am thinking that in both you would have the bend flowing right through otherwise you would be blocking the movement.  Would trying to keep the neck straight make it difficult for the horse to unweight the shoulder?

Many thanks,

Wendy


Hi Wendy,  I am glad you asked these questions because they were similar to the ones I have been tossing around in my head as I review the pictures.  Did this get answered and I missed it one of the other answers?  Sometimes all of this bends my brain in a hurtful way, lol.

Kathy 

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Deb,

 

      I wasn't real sure where I was going with it but it made a few connections in my head. What I have been searching for is how the intangible of energy is moving and being directed throughout the body and at first I thought perhaps rotation could be serving as the director of energy. However, I have been experimenting with my own body(oh I feel so dirty) and have come to realize the thing that is directing my energy is my intent.

    At first I began by taking a step and I could feel the rotation but then my arm would compensate for it when I was thinking about going forward. If I then thought about turning the same movement would allow me to turn. My intent was directing the motion. So the notion then becomes that the art of training is getting the horse to accept our intentions over his own.

I would like to say that I don't think that 15 to 30° is a small amount considering that is only one side so the you have to double it for the entire range of the rotation. It is also intrigued me in regard to the functioning of the curvatures of the spine. Rotating a straight rod is one thing rotating a rod with curves  is another. I have to think on all this more.

David Genadek

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DrDeb wrote: Dorothy, no part of the horse's spine is really designed to permit rotation EXCEPT one single joint, and that is the one between the atlas and axis at the front end of the neck. At that joint, rotation is the ONLY motion permitted, and quite a wide arc too.

The accessory articular processes of the thoracics are quite different from those of the lumbars. Whereas the facets on the lumbar ones are oriented nearly vertically, the facets on the thoracic ones are oriented nearly horizontally. Both quite effectively inhibit rotation.

However, whereas lateral flexion is absolutely forbidden within the sacrum (because its five vertebral elements are fused together), and forbidden among the sacrum and last three lumbar vertebrae (due to the presence of the inter-transverse articulations), and inhibited among the first three lumbars (due to the lumbar accessory facets) -- it is perfectly OK among any of the thoracics. It is also perfectly OK between the last thoracic and first lumbar, and in fact this joint can act almost as the hinge to the garden gate -- when you are standing to the side of a horse and he wants to kick you, the first thing he does that lets you know you ought to be backing out of there pronto is he'll cock his arse toward you. The 'cocking' is a sidestep he makes with the entire hindquarter, considered from the dock forward to the lumbo-thoracic joint, and hinged upon that joint. The horse who can do a really free half-pass also uses this joint plus any lateral flexibility he can squeeze out of the first three lumbars.

  Much more profitable is to look at the horse's spine in detail, just as you keep asking about Dorothy, and I wish more students would do what you are doing. -- Dr. Deb
Learning to understand (and appreciate) what the spine can do is a fascinating study!  Thank you to every one who's added to the discussion - didn't know how much I didn't know until reading here....now I have more questions:

1. If the joint between the atlas and axis allows a rotational movement only (if I understood correctly) Then is it the connection of the Atlas to the skull that allows the horse to move his head/nose up and down. eg. to move the nose from pointing toward the ground to pointing straight outward. Is this kind of a hinge joint? I have never seen it.

I have the "Horse Anatomy, A Coloring Atlas." Kainer, McCracken. If there is anything in there that is useful for explaining this.

2. Are there pictures here somewhere of the Accessory Articular Facets of the Thoracic Vertebra? (horizontal orientation is what i want to see) I saw the pic of the articular facets on the lumbar vertebra (vertical orientation)?
 
I think I found a pic of the lumbar vertebra "Articular processes (Dens of the axis)" on plate 7 of the book. Not sure what "Dens" means.

Thank you in advance for your help on this....:)
Betty Ann



DrDeb
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Yes Betty Ann, good, you've been studying the anatomy books. That's real good.

"Dens" means "tooth". Projecting forward from the front lower edge of the axis vertebra in humans there is a prong that kind of looks like a fang. That's how it gets its name. It is not really a tooth; just a formation of the bone. Many names in horse anatomy or mammalian anatomy generally are taken from the human terminology, not always perfectly aptly. The horse's "dens" is shaped more like a wide spoon.

The dens projects into, and seats in, the lower half of the rear part of the atlas. Picture holding a serving-type tablespoon in your right hand, convex side down. Cup your left hand under the convex part of the spoon. Your left hand represents the atlas and the spoon the dens of the axis; this is a good picture of the actual arrangement.

It is upon the dens that the atlas + skull rotate. When rotation occurs, it is the skull + atlas moving together, locked together. They are locked together because rotation is not a permitted movement at the joint between the skull and the atlas.

Movements that are permitted at this joint are extension and flexion (poking the nose out and tucking it back), and twirling (swivelling of the skull around its long axis). Note that twirling and rotation are NOT the same action. In twirling, the skull rotates about its own long axis; in rotation, the skull + atlas rotate about the (projected) long axis of the axis vertebra.

What you have found with an anatomy book is that although the book may feature many things, movement is not one of them, because it is a book. A book is two-dimensional and it isn't a videotape. To really learn about horse anatomy, one must have an actual skeleton. You get a start on that by doing what others who correspond here have gone out of their way to do: visit museums of natural history, where mounted skeletons can be seen. You look at them, you make sketches, and if it is permitted, you take pictures (it generally is permitted so long as you turn off the flash).

You can also download the PDF's from our "Knowledge Base" section on evolution. Those PDF's contain many photos of skeletal mounts taken at various museums. This is not as good as being actually at the museum, but it might be helpful.

This is the beginning. After that, if you want more, you'll have to find a museum that offers a public-handling area or public-learning area, where they will have a staff member during certain hours who will supervise you as you handle actual box specimens. A box specimen is a skeleton that hasn't been mounted, just loose bones in a box. These are valuable because, even though the mounted skeleton shows you the correct relationships between the bones, it cannot move or be moved. You cannot open or close the joints on a skeletal mount because of the steel armature that holds it up. However, you can find pairs of bones in the box, i.e. for example the femur and tibia, and with your hands hold them in articulated position, and then manipulate them until it's clear to you how the joint functions. This is how all University students enrolled in anatomy programs, be they aspiring vets or zooarchaeologists or vertebrate paleontologists, learn it.

The museum where you find the "learning center" may or may not have horse bones specifically available. It won't matter. Learn the dog or the cat, and most of the principles will still apply. Then after that, you can come and take one of my anatomy classes where we specifically study horse. -- Dr. Deb

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Very valuable pictures to be printed in this thread!!!!
Brilliant.




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