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Racinet's tri-dimensional law
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David Genadek
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 Posted: Sun Jan 17th, 2010 08:47 pm
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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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 Posted: Sun Jan 17th, 2010 08:55 pm
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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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 Posted: Sun Jan 17th, 2010 08:59 pm
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Wonderful clip there, David! Thank you very much! What a pleasure! -- Dr. Deb

Dorothy
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 Posted: Mon Jan 18th, 2010 06:53 am
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Thank you both David and Dr Deb

kindredspirit
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 Posted: Mon Jan 18th, 2010 01:47 pm
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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 

David Genadek
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 Posted: Mon Jan 18th, 2010 03:21 pm
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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 429 times)

Dorothy
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 Posted: Mon Jan 18th, 2010 04:06 pm
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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

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 Posted: Mon Jan 18th, 2010 08:25 pm
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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 421 times)

CarolineTwoPonies
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 Posted: Tue Jan 19th, 2010 04:29 am
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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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 Posted: Wed Jan 20th, 2010 06:11 am
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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

Dorothy
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 Posted: Wed Jan 20th, 2010 07:27 am
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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

 

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 Posted: Wed Jan 20th, 2010 08:56 am
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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

Seglawy Jedran
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 Posted: Wed Jan 20th, 2010 03:18 pm
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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

DrDeb
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 Posted: Wed Jan 20th, 2010 06:46 pm
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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

Dorothy
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 Posted: Thu Jan 21st, 2010 10:47 am
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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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