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The Long and Low Position
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DrDeb
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 Posted: Tue Aug 28th, 2018 03:59 pm
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Yes, 'enthesis' is the $10 word for 'connection' in the anatomical sense. And the description given by the Wikipedia authors is helpful, especially where they mention that there is a gradual transition from one tissue composition to the other, i.e. for example from tendon to periosteum or from tendon to bone.

But they don't go into much specifics about the other end of the tendon, i.e. where it "attaches" to the muscle, and the reason for this is that it does not "attach" in any sense that you could attach to the word "attach". An "attachment" implies that two things are being joined -- stitched together or riveted or glued in some way. It implies that there is some sort of abrupt boundary. But that is not at all what happens as we go from muscle belly to tendon, and this is the crux of the matter that I am after having you realize.

Muscles in the gross are hierarchical in structure. In other words, if you pick a muscle that has a name, say the biceps brachii in your arm, the anatomy book is going to tell you that it has 'x' attachments (called origins) at the top, where it comes off the scapula, and 'y' attachments (called insertions) at the bottom, where it goes into the radius. So between the scapula and the radius, lying upon the humerus, we have the belly of the biceps brachii. That's the gross structure.

Always when you see skeletal muscles pictured in an anatomy text, and this is quite real also if you were to be in the actual dissection lab and see the real muscle exposed, it has a striped or striated look. This is because every skeletal muscle is in reality a bundle of muscle fibers; and each of those fibers is itself a bundle of muscle cells. And this is the hierarchical structure -- bundle of muscle cells, bundled into a muscle fiber; bundle of muscle fibers makes up the muscle in gross.

Now each muscle cell is a long, spindle-shaped affair if you were to dissect it out separately. And what you would notice if you did that would be, that the ends of the spindle looked pale or whitish in color, while the thicker middle or 'belly' of the cell had a pinkish or red color, which is due to the location within the middle part of the cell, of the mechanism which makes it possible for the muscle to contract when stimulated. The contractile mechanism is invested by an incredibly dense network of tiny blood vessels which bring the sugars and oxygen which the cells require in order to do their work of contracting.

The contractile mechanism and its investment of blood vessels fill almost 100% of the space within the 'belly' of the muscle cell. And, of course, like all other cells, the contents of any given muscle cell are held together -- 'bagged' -- by the cell membrane, which is said to be 'intelligent' in that it has the ability to allow certain substances to enter the cell while barring others. Enwrapping the cell membrane and supporting it, external to it, is an outer 'bag' formed of collagen and elastin fibers which is called the endomysium.

If you look in Wikipedia you'll encounter three similar terms around this aspect -- endomysium, epimysium, and perimysium, but in reality they're all the same in terms of their chemical composition and their physical structure. The different names are applied because each hierarchical level of the gross muscle has its own 'external bag' wrapping. The names thus don't matter terribly much, but what does matter crucially to the question being asked here about 'long and low' is that there isn't any substance in the body more stretchy than endomysium (or perimysium, or epimysium, whatever level of wrapping you're looking at).

In short: the structural walls of muscle cells are incredibly stretchy. This is obviously necessary to permit the muscle, in gross, to bulge up in the center when fully contracted. But the opposite applies too: the muscle must be stretchy enough to be capable of being lengthened, because almost all skeletal muscles are opposed by some other skeletal muscle which, when it contracts, acts to stretch the given muscle. In short, every flexor muscle has opposed to it an extensor muscle which acts upon the same joint.

But this still isn't as far as we need to go just to get to Square One with your question. Let us perform a mental experiment and say that we have dissected out a single muscle cell and it is lying on the lab table before us. Now we take an aspiration needle or a very fine pipette, and we puncture into the 'belly' of the cell, right in its middle, and we use our needle to carefully suction out all the contents of the muscle cell. This will leave us with the empty cell membrane and its external investiture of endomysium -- a long, spindle-shaped empty bag made mostly of endomysium.

What color is the endomysium? Grocery-store plastic-bag white. Where does the endomysium end? It doesn't end anywhere; once the reddish cell contents are sucked out, it becomes clear that they only filled the center part of the long, spindle-shaped cell. The ends of the cell are what people call 'tendons' or 'tendon fibers', but there is no such thing as a tendon, or a tendon fiber, existing on its own independent of or separate or disconnected from the endomysium that forms the whole rest of the cellular 'bag'. It is all one continuous whole, from the upper tendon or tendon of origin, through the center length of the cell, all the way down to the lower tendon or tendon of insertion. It is all one, single, continuous, tough, stretchy bag.

So, in this sense, there is "no such thing" as a tendon. The horse's forelimbs below the knees do not have "tendons". The Achilles band above the hock is not a "tendon". And so on for everything in a horse that horse people and horse magazines of the common sort call "tendons": they do not exist. What DOES exist is muscles, which are hierarchical in structure i.e. they are bundles of cells, whose ends are flatter or skinnier than the bellies of the muscles because they do not contain the red cellular juice. Thousands of muscle cells which compose even the smaller skeletal muscles are bundled together so that the bundled upper ends comprise tendons of origin and whose bundled lower ends comprise tendons of insertion. Every
"tendon" is, thus, properly called and most usefully thought of, as the tendon OF A MUSCLE. So the correct name of one of the structures on the back of a horse's cannon bone is "the tendon of insertion of the superficial digital flexor MUSCLE."

Now we are halfway there as far as realizing why I asked you to define the word "attach" in the anatomical sense. What we have found out is there is no "attachment" but instead, total continuity from one end of the muscle cell to the other.

The second half, then, is this, and it's your new question to answer: what is a muscle -- I mean in terms of its function -- that is completely at rest, not contracting at all but just quietly resting? What function can a muscle in this state potentially perform that it ABSOLUTELY CANNOT perform when it is contracting?

As always when I ask a question -- don't overthink this and don't make it more complicated than it is. The answer should be obvious from the foregoing discussion. Cheers -- Dr. Deb


iwanttolearn
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 Posted: Tue Aug 28th, 2018 07:02 pm
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"What is a muscle -- I mean in terms of its function -- that is completely at rest, not contracting at all but just quietly resting? What function can a muscle in this state potentially perform that it ABSOLUTELY CANNOT perform when it is contracting?"

Hm... this is tough. I'm afraid I don't really know. I mean, I do understand a little. The tendons do not exist on their own, not unless viewed as extensions and structural supports of the muscles. What we call tendons are "one continuous whole, from the upper tendon or tendon of origin, through the center length of the cell [muscle], all the way down to the lower tendon or tendon of insertion. It is all one, single, continuous, tough, stretchy bag".

So I think to myself, perhaps the function of the muscle at rest is to stretch this 'bag'. But the muscle stretches the bag when it is contracting, too, because the endomysium needs to accommodate the bulging shape, so that is not the answer. But now I realize I am thinking of the endomysium and tendon as much the same thing.

Maybe the function of the muscle at rest has to do with force dissipation. But this is not something you mentioned, and you said, "the answer should be obvious from the foregoing discussion". So again I think I'm on the wrong track, even though I do have a somewhat amusing image in my head of the Newton's cradle thingy, those metal balls on strings that knock into each other back and forth. That's how I imagine the output and input of energy dissipation between the tendons and the muscles.

Put otherwise: for all the information you have presented me with, I do not know the correct answer. If anyone else who is reading can answer, I'd be very much obliged.

Last edited on Tue Aug 28th, 2018 10:09 pm by DrDeb

iwanttolearn
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 Posted: Tue Aug 28th, 2018 07:21 pm
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In terms of the muscle hierarchy, should I be thinking on the cellular level or the gross structure? Or does the concept you're trying to get me to understand apply to both?

DrDeb
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 Posted: Tue Aug 28th, 2018 10:08 pm
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Once again, you're overtrying and overthinking. It's a bad habit of students who are worried that they'll be punished in some way for failing, that they give a scattershot answer -- just try anything and maybe they'll get "credit" for partial-correct. The image you posted is not relevant to our discussion, nor either to the question. Since it takes server space, I have deleted it.

The answer is much simpler and is a direct conclusion of the lecture which I gave above.

Again: What is a muscle IN TERMS OF ITS FUNCTION when it is not contracting? In other words: HOW DOES A MUSCLE FUNCTION when it is not contracting? It functions -- like a WHAT? -- Dr. Deb

iwanttolearn
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 Posted: Wed Aug 29th, 2018 01:16 am
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Like a tendon?

DrDeb
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 Posted: Thu Aug 30th, 2018 04:00 am
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Yes! Correct. A muscle which is not contracting is simply a stretchy bag. Is a muscle "all tendon" or is a tendon "all muscle"? Moot point when contraction is not happening.

This leads us to several new insights. In terms of teminology, we speak of a muscle that is contracting as "active", but we speak of tendons and/or muscles that are not contracting as "passive." Muscles coordinate in various areas of the body to form functional systems, and therefore, each of those systems (because it contains muscle in addition to sometimes also having bone, ligament, periosteum, or other connective tissue) can be "active" at one moment but "passive" at the next.

Second, it causes us to notice an error that is in every single existing published equine anatomy textbook, and an error that has been repeated by every secondary source (i.e. the common sort of magazines and all the books that I know of that have been recently published that purport to explain equine biomechanics or physiology). The error is this: that the anatomy book talks about "ligament" as if it were one single kind of tissue. And its author will do this despite, in some cases, also telling the reader that for example the suspensory ligament is likely to once have been -- in animals ancestral to Eohippus -- muscle tissue. This likelihood is raised to a certainty not only by detailed study of the bones of the forelimb in phenacodontid condylarths and an array of fossil equines from the earlier half of the Tertiary Period, but also by histological and chemical examination of the suspensory ligament tissue from modern horses. "Histology" studies the microstructure of a given tissue, and this type of analysis shows that suspensory ligament tissue is very different from a sample taken from an annular or collateral ligament. Likewise, chemical analysis which is done by grinding up the sample, macerating it, and then using electrophoroesis to discover its molecular makeup, shows gross differences between suspensory ligament tissue and annular or collateral ligament tissue.

In short, the error in the anatomy books is that they conflate what are really two categories of tissue into one, and they do this because they are beguiled by that rotten Pony Club definition that says, 'a ligament connects bone to bone.' Now, it should already be obvious that this is not a useful definition because that is exactly what almost every muscle does, too.

Now I am going to lead you through the same thought-experiment that we did before, but to a new purpose. Remember pipetting the red cell contents out of the muscle cell. Now think of doing that for every cell in a muscle. What you are left with  is tissue that is identical to the suspensory ligament, and which should properly be termed "yellow ligament." Every yellow ligament in the body was once a muscle; yellow ligaments are muscles that have lost the ability to develop sarcomeres/contractile apparatus. Yellow ligaments are the empty, highly stretchy, epimyseal bags which perform the function in the body of rubber sheets and of stretchy bungee-cords.

Thus, a proper and correct classification of the tissues we are discussing would be:

1. Muscle tissue, which includes "tendon", which are the "empty bundled ends" of muscles;

2. White ligament tissue, which has almost zero content of the molecule elastin but has a high content of collagen; which is not at all stretchy but can be very strong if pulled parallel to its fiber structure; however it is liable to tearing if it experiences forces at an angle to the fiber structure. The manufactured functional analogue to white ligament is fiber-tape. The function of this kind of tissue is primarily to hold one bone to the next.

3. Yellow ligament tissue, which has a high content of elastin although also structured (as all connective tissue is) by collagen. Yellow ligament is highly stretchy and can stand not only direct but crosswise or twisting pulls. What it can't stand is overstretching. Whereas white ligament is usually sheetlike, yellow ligament tends to be thicker even when formed as a sheet; otherwise it looks like a rubber trucker's tiedown or bungee cord with a circular cross-section.

At this point it's time for more homework:

1. Please go to http://www.equinestudies.org, click on "knowledge base", and then click on the button that says "The Ring of Muscles". Read this paper and particularly, study the illustrations.

2. One of the major points made by this paper is that when a horse coils its loins, that is the essential basis for collection. In order to coil the loins, muscles on WHICH SIDE of the spine are activated (i.e. muscles that root above the vertebrae, or muscles that root below the vertebrae)?

3. Muscles located WHERE must actively contract in order for a horse to arch the freespan of its back?

4. Muscles located WHERE must totally shut off in order for a horse to arch the freespan of its back?

5. What will happen if the correct muscles do not completely shut off, i.e. completely relax?

This should lead you right up to major insight as to why the original photo you posted, of the bay-colored horse "going long and low" is a picture of remarkable ugliness. The poor horse! But not for the reasons you originally thought, or the reasons you heard on the Internet! Cheers -- Dr. Deb

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 Posted: Tue Sep 4th, 2018 03:20 am
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Thanks for starting this thread, Anne-Marie. It has been a great reminder and I am watching the next bit of the discussion with interest. I have only just logged in to see the picture you posted to start with and as I am always in a hurry I just looked at it and thought that looks yuk but didn't really sit and look at it as to why it looks yuk. I am now processing the why. Your youngster is beautiful.
Kind Regards
Judy

DrDeb
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 Posted: Tue Sep 4th, 2018 05:37 am
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Yes, Judy, I have been waiting not only for "I want to learn" to ask the obvious question, but also for anybody else to ask the obvious question. Let's get on to WHY I said the bay horse posted as an example of 'long and low' is 'remarkably ugly.' And remember: it has totally got to do with what was said in the foregoing posts. The horse is not innately ugly, but there's certainly a problem with his VERSION of 'long and low'. Cheers to everybody who has their thinking cap on around this. -- Dr. Deb

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 Posted: Tue Sep 4th, 2018 05:50 am
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When I look at this picture I see tension all through the horse's body, it looks like the muscles below the spine are being used as he has a line in his belly but it also looks like the muscles above the spine are not released, especially in his neck. The flow of energy doesn't come out of his withers like a fountain and his expression is not mellow and okay.
Cheers Judy

DrDeb
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 Posted: Tue Sep 4th, 2018 06:09 am
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Yes. Absolutely, Judy. 100% correct.

The ugliness equates to a high level of tension: emotional and psychological tension (on the inside) and visible, palpable muscular tension on the outside.

Going 'long and low' in this manner is worthless to training, and destructive of both the inner life and the physical life of the horse.

Anything we do with a horse that is NOT done from the softness, that is NOT the result or aftermath or side effect of FIRST having obtained the softness, is ugly and worthless and destructive.

This is an essential point that can so easily get lost anytime someone has the ambition to compete. Fulfilling the goals of the competition -- whatever they are, whether it's on the particular level of fulfilling the requirements of a test or class, or whether it's on the more general level of 'point chasing' -- can so very easily overwhelm the real goals that brought us to horses in the first place, which are enjoyment, pleasure, joy, 'flow', mutual understanding, and athleticism expressed within the envelope of release.

So. In shorter and less romantic language, or if you like in more 'scientific' language, what the bay horse is doing is 'clashing his own aids', or clashing or mis-using the Ring of Muscles biomechanical system which is what creates and modulates collection in the physical body.

What our young questioner, Anne-Marie, needs to learn is to stop hanging out with people who don't make this distinction, for it will be fatal to her career as a horsewoman, i.e., a woman that knows about, lives for, and manifests horsemanship rather than competitorship, which is the desire to use horses to make oneself look good or feel good by winning prizes or social approbation from the dominant culture. One of my main aims as a teacher, particularly where young learners are concerned, is to teach them not to idolize what the world calls 'success', but rather to teach them what real success means.

So now, I am hoping that all of those who are reading this thread -- and there are quite a number of you, I know, who understand what has been said here very deeply through having decided to live it yourselves -- if you would like to do Anne-Marie a great favor and give her a great gift, do please post your favorite photo of 'long and low' or a horse stretching into the bridle while moving on with good life in the body, so that Anne-Marie can see what it should look like.

For what she has learned here, or one thing anyway, is that 'long and low' is not always the same thing; so we cannot either object to it, or approve of it, when somebody wants to engage us in an argument such as might go on in some other board -- a silly argument, an argument that just goes round and round to no purpose, because the terms have not been carefully defined. We have to actually see the horse to know whether he's moving right and feeling right.

And I know you guys have got pictures of that, and what a great thing to share! So please post away, with my thanks. -- Dr. Deb

JTB
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 Posted: Wed Sep 5th, 2018 12:50 am
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I thought this would have been easy but it was interesting to Google 'long and low' and see what images appeared. Yikes!!!
I will now turn to my own collection of images and see what I have got, there must be a picture somewhere. :-)

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 Posted: Wed Sep 5th, 2018 09:22 pm
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This is all I have, just a cell phone picture under low light conditions, not sure whether it qualifies exactly. I never get tired watching Buck ride, and that session was particularly beautiful.

Isabel

Attachment: Guapo walk cows 2017small.jpg (Downloaded 89 times)

JTB
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 Posted: Thu Sep 6th, 2018 09:00 am
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One can never get tired of watching Buck ride! :-)
From my collection I have a few pics. How many can I post!?

Attachment: IMG_9278.jpg (Downloaded 81 times)

Last edited on Thu Sep 6th, 2018 09:02 am by JTB

JTB
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 Posted: Thu Sep 6th, 2018 09:06 am
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Pony 2

Attachment: 004_1.JPG (Downloaded 81 times)

hurkusdurkus
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 Posted: Fri Sep 7th, 2018 12:39 am
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This is not strictly 'long and low', but I remember the feeling as my horse was traveling downhill.

He is taking an extra large, giant step behind because he is stepping over a big rock.
His thought was following my intention as we went winding left and right through the sagebrush down the hill. I didn't much have to steer with the reins, and it seemed like his head was easily twirling as I would ask him to change direction.

Attachment: Downhill 2.jpg (Downloaded 71 times)


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