Force, Stress, and the Hoof, Part 2

So far, we’ve been talking about the hoof as if it’s a single structure, even though we know it’s really a composite of different parts.  The terminal phalanx that I wrote about in my October 18 post, known as the horse’s coffin bone, is sheathed in a highly complex nest of tissues that are designed to safely handle stress. You can see in the stylized cross-section to the left that the “hoof” is made of hoof material itself, ligaments, tendons, bone, connective tissue, and skin.  Many of these tissues are made of combinations of collagen and elastin, two types of fibers that both stretch and absorb energy in different ways.  Cartilege is also a large component of these tissues, increasing with the age of the horse.  (See this paper by Robert Bowker, VMD and PhD at Michigan State for more details.)

It is exceedingly difficult to measure the strength of such compound structures. In our last post we therefore generalized about the hoof as a whole to get a rough idea of what’s going on. And we’ll do that again in future posts.  But in this post, we’re going to consider the issue of how various parts of the hoof transmit stress.  Then we’ll return to considering the hoof as a whole.

In that first diagram above, the terminal phalanx or coffin bone is labeled p3 (for phalanx 3).  You can see the hoof wall material all down the front of the hoof in front of that bone, and the frog is beneath it.  A thick pad of special tissue called the digital cushion is also between the p3 and the ground.  It’s important to remember that the hoof wall extends all the way around the foot, though, which you can’t see in the section shown above.  It’s also important to remember that the horse has a sole across the bottom of its foot that isn’t very visible in the section above.  Both are shown in this bottom-of-the-hoof view from the University of Missouri Extension website.

Roman “hipposandal” boot-like hoof covering made of metal, about the first century CE.  From Wikipedia.

The history of putting protective coverings over the hooves of horses is nearly as contentious as contemporary discussions of whether horses should be shod, go barefoot, or wear boots.  In 1934, Professor A. D. Fraser wrote in Classical Journal about the academic wrangling going on even then — 80 years ago! — about whether the Romans shod their horses or the practice began in much later Medieval times.  But one thing that is clear is that two different types of hoof coverings have been used by Eurasian cultures when they did anything at all to a horse’s hoof.  There were boot-type coverings that went across the entire bottom of the hoof, and shoes that were nailed only to the hoof itself, leaving the sole bare and elevated above the ground. Of course, we have both types of hoof coverings available to us today, for our horses, although it’s only in the last couple of decades that boot-type coverings have reappeared after being absent for quite a long time.

One of the most striking things about the underside of a horse’s bare hoof is the flatness or concavity of the sole.  Some barefoot horses have flat soles that touch the ground all the way across, whereas others have slightly concave soles that are domed so that only the frog touches the ground.  Of course, the imprint of the frog is visible in a barefoot horse’s print, regardless, because it is made of different material that leaves a distinctive impression in the dirt.  You can see the impression of the frog and of the outer hoof wall on the modern hoofprint image (from a barefoot horse) in the top picture of the set to the right.

What’s interesting to me is that you see much the same shape in the image directly beneath that one.  That image was carved into rock about 24,000 years ago in Le Cellier Cave in France, and is almost always identified by archeologists as the picture of a vulva.  (You can see several other similar images carved into the same rock in other areas if you look closely.)  But in that same cave, there is another carving of the same shape made over the top of a horse’s head and neck.  A drawing of the shape is third in the column of images, and a photo of the original stone is beneath it at the bottom.  An archeological description of the piece says “. . . it is a stone much less voluminous, carrying a bizarre design. The image appears to be the head of a horse, and on the right a vulva not well represented. These designs are united by a line which seems to indicate a real relation existed between the two.”  One is tempted to speculate that the “real relation” might be that both images represent parts of the same animal.  (You can read more about these shapes and other items found in the cave at a page of the Don’s Maps archeology website.  The hole in the hoof/vulva is thought to have held oil, the stone being a small portable lamp.)

There’s no particular reason here to argue that these hoof-like shapes are actually hooves, that their having been carved into stone tells us something about how these ancient people felt about horses, or that the level of assurance with which contemporary archeologists identify the shapes as vulvas is also meaningful.  But the carvings at least suggest the fact that people have been paying attention to the shape a horse’s hoof makes in dirt for quite a long time.  And of course, horse hooves are important symbols to people even today — as you can tell by looking up “horse jewelry” online and counting the number of horse-hooves and horse-shoes that come up.  (I should note in passing that there’s a good deal of professional and lay argument about shapes like the ones from Le Cellier even in ancient Celtic art that’s only about 2000 years old, with an additional level of discussion about a possible metaphor that may have linked women, fertility, and horses.  But that’s fodder for a different post.)

The point is that the sole of a horse’s foot doesn’t always touch the ground, even when the horse is barefoot.  And we all know that the sole can be bruised or “sored up” in some way by sharp or stony surfaces.  In fact, one of the reasons shoes or boots are used is to protect this sole.  However, it’s interesting to notice that there is a likely biomechanical reason for any concavity of a horse’s sole.

At left is a diagram (modified from one on a Federal Transportation Authority webpage) of two different types of reinforced concrete beams.  The one on top is a “regular” beam that is cast in a flat shape.  When force is applied to the beam (because it is helping to hold up a bridge, for example), the stress causes the beam to bend or bow in such a way that it cracks on the underside.  The black arrows in that diagram show the force being applied, and you can see the way the cracks are represented.  This really does happen in beams that experience loads greater than they can bear.

However, if the beam is cast in a bow or curve that faces against the direction in which it will be loaded, there’s a different outcome.  This type of beam is called “prestressed” to indicate the way it can “resist” the stresses caused by bearing a load.  Now when the load is applied (again, see the arrows), the stress flattens out the beam instead of bending it.  So cracks do not form.  Many domed or bent structures are actually designed to resist force.  Skulls, for instance, are domed outward to resist the stress of fairly large force against the head from the outside (as from falling and hitting the ground).  So you can see that the degree to which a horse’s foot is slightly concave on the underside allows it to carry stress better without failing.  This doesn’t mean that a flat sole that touches the ground all the time is “bad”, though.  In fact, a hoof that’s slightly concave when you pick it up off the ground to look at it might flatten out and touch the ground when it’s bearing the horse’s weight.  We are not establishing a value system here, but merely considering the possible adaptiveness of certain aspects of hoof structure.

One of the more interesting things to consider is how a typical metal horseshoe affects the way that stress is transmitted through the horse’s leg.  Gail Snyder, a hoof care professional who also has a Mechanical Engineering degree, wrote an excellent overview of this difference in a 2012 issue of Natural Horse (that you can download here).  She assumed that a typical barefoot horse has a flat sole and therefore distributes force across the entire surface area of the hoof — just as we assumed in our calculations of Part 1.  She assumed a smaller sized foot for her calculations than I did, so her figures came out slightly different, but the important issue is how adding a horse shoe changes the stress in a horse’s foot.  Once a horse shoe is in place, as shown in the figure to the left (from her paper), the surface of the foot that’s in actual contact with the ground is much smaller, restricted to the bottom of the shoe itself.  The stress in the weight-bearing part of the hoof therefore goes up — by over 230% — simply because the shoe is so much smaller than the whole foot.  (Remember, Stress = Force divided by area.  The shoe is smaller, so the area is smaller, which makes the Stress larger for the same Force.)

There’s an intriguing corrollary to this, too.  To understand it, you have to realize that force also comes up into a horse’s foot and leg from the ground.  If you hit the wall next to you with your knuckles, reading this, you will feel what I’m talking about:  you hit the wall, but the wall also “hits” you back and smacks your knuckles.  (If the wall did not “hit” you back with the same force that you used against it, your knuckles would go through the wall.  The wall would not resist your force with one of its own.)  If you hit the wall harder, the wall “hits” back harder.  A person who’s really angry may hit a wall so hard as to suffer bruises and possible broken bones as a result of the fact that the wall will hit them back with the same huge force.  You might remember this returned force from studies in high school: Newton’s Third Law of Motion states that for every action there is an equal and opposite reaction.  When it comes to forces that react to an animal standing on the ground, such a reactive force is called the ground reaction force.

So not only does a horse experience force, and therefore stress, from gravity pulling down on its body mass so that its feet strike the ground, a horse also experiences force and therefore stress from the impact of hoof on ground in which the ground exerts force against the horse.  You can see this, and very clearly, in an astonishing series of slow-motion video images made by Sky Sports UK of Hickstead horse jumping, at YouTube, here.  I tried, however, to capture some small piece of what’s visible in a series of three images that are reproduced to the right.  When the horse’s hoof comes down and hits the ground, you can see a wave of force returning up the horse’s pastern, from the ground impact.  I have pointed to one of those waves with a red arrow in the second image.  The apparent distortion of the top of the pastern area in the last image is due to similar waves continuing to propogate through the soft tissues.  If you watch the video, you will see that these waves move upward and are caused by force coming from the ground, due to impact.

(Yes, the fetlock drops very low in the last image.  We will not discuss that here, as it’s an adaptation related to elastic storage of energy.  All you need to know right now is that this image does not show a dangerous degree of flexion.)

The interesting thing about what you see in these images is that the ground reaction force is being transmitted upward through the skin layers of the horse’s foot and leg, as well as through the stronger bones in the “core” area.  It’s possible that there’s proportionately more “shallow tissue transmission” when the ground reaction force is directed ONLY through the shoe, since the shoe is going to transmit  force through the hoof wall it’s nailed to, and this force is then very likely to be transmitted on upward through the skin and deep dermal tissues that are in line with the hoof wall.  If so, then the wraps or boots around the cannon of such a horse may well keep those forces from adversely impacting tendons that aren’t designed specifically to transmit those forces but are quite coincidentally sitting in their path.  (If anyone who designs such boots and knows the biophysics of their design elements wants to educate me about this, I’d love to know what data exist.)

On the other hand (and there is always an “other” hand), remember that the terminal phalanx sits just inside the front portion of the hoof wall.  So forces being transmitted through the hoof wall will also, at least to some extent, enter the chain of bones nearby.  The question is how ground reaction forces are transmitted through the legs and feet of shod and unshod — and also booted — horses.  And as far as I know, we don’t have good data on that.  But it’s certainly something to bear in mind when you’re weighing the decision each of us has to make about shoeing, booting, barefooting, or whatever.  While you are taking into account the kinds of surfaces you ride on, your horse’s personal history and past injuries, and the sorts of activities in which your horse engages, remember that the different kinds of things we put on our horse’s feet change the way that force is transmitted — to the ground and also back up into the horse.  There aren’t any easy answers.  But it is probably safe to say that it’s more important to take extra steps to protect the hoof wall and tendons if your horse wears standard shoes than if it goes barefoot.

Next up:  What happens when the horse starts moving

When Is a Horse Like a Tornado?

I had a friend several years ago who was an artist, who became absolutely captivated by tornadoes after we saw one once, and lived to tell the tale.

I am supposed to be writing about horse hoof stresses in this post.  I’ve sat here quite a while today, typing variations of the lead sentence: “There are several factors that influence the stress on a horse’s foot.”  And it just won’t go anywhere, because it’s “the artist and the tornado story” that wants to come out today. You’ll see why by the end of the post. Trust me.

The artist and I stood literally shoulder to shoulder for what felt like a week, mesmerized, watching the clouds spin down beneath the central updraft, coalesce into a funnel, fall apart, and pour upward back into the core like an inverted waterfall, over and over again.  It wasn’t a very big tornado.  That was probably a good thing.  (Don’t try this at home, adult supervision only, your mileage may vary, etc.)  I have to admit, it was an astonishing thing to see.  As far as I know, the artist never quite got over it.

Every time I talk to people about horse biomechanics, something comes up in our conversation that makes me think about form and function . . . and the enormous problem people have with remembering that the “function” part matters.  A lot.  The artist brought this aspect of peoples’ thinking home to me real fast that day, maybe the first time I’d ever realized how separated form and function can be if people aren’t used to thinking about it.  Because after the funnel was carried away on the moving squall line, and the storm had rained itself out over the tops of our pointed little heads (we were lucky not to have been pulverized as well as mesmerized), the artist turned to me with rivulets streaming out of her soaking hair and running down her forehead, and asked, “Why is a tornado shaped like a triangle?”

She was thinking about the shape shown in the NOAA photo to the left.  It’s a common enough shape for a tornado, but it’s certainly not “standard”.  Here are more NOAA images to give you an idea of the range of variation.

The thing that really threw me about the artist’s question was that the tornado we’d been watching as it tried to form and kept falling apart never looked like any of these pictures, though.  It looked a lot more like the still image below from video of a rotating wall cloud near Terre Haute, Indiana in 2007.  The red arrow points to a dark circular structure with a fairly narrow, paler rim of clouds that can be seen, in the video, to be rotating slowly with the entire cloud immediately surrounding it.  (It is, in fact, an example of the infamous “rotating wall cloud” of severe weather alerts.)  This is where a tornado funnel can form.  It was a structure like this that we saw forming “sides” several times before falling apart and “pouring” over its own lip and up into the clouds again, a number of times in succession.

In other words, the image we actually saw, the artist and I, was one of circular rotation.  Furthermore, it was absolutely clear as crystal to both of us that within the “funnel-to-be” that kept forming and falling apart, the overall direction of movement was up.  And that is how tornadoes work, really.  They are a vortex, having a spiralling motion that goes from the ground up into the clouds, spinning as it goes.  It is the spinning winds of the vortex that create the distinctive “tornado vortex” signature on radar that identifies a tornado’s likely existence even at night when it can’t be seen by weather spotters.  Because the tornado is spinning in a circle that’s parallel to the ground, Doppler radar shows winds on one side of the funnel as going away from the station, and winds on the other side of the funnel as coming towards the station.  Since the radar creates different-color images for winds blowing away and winds blowing towards, there are two different direction-colors of wind smack next to each other on the radar.  That’s the vortex signature, and it’s created by the rotating circle of wind.

Interestingly, about five years before the artist and I encountered the nascent tornado I’ve described, I had spent several long months putting information about things like “tornado vortex signatures” onto a series of educational pages for the non-profit I worked for, using tornadoes to explain the power of intergrating different ways of knowing, learning about, and responding to the natural world.  The artist knew that I had spent hours going over reference materials, talking to experts at NOAA and the NSSL, and writing everything up because she had proof-read and edited every one of those pages for me at the time.

So although I understood why she figured I would have at least a semi-reasonable answer to her question, “Why is a tornado shaped like a triangle,” at the same time I was stunned.  Because not only had she read, in detail, about how tornadoes function, she had just seen it with her own eyes:  rotation and updraft, both.  Yet somehow she had fastened onto a stereotypical shape she’d seen somewhere, a form — one she certainly hadn’t gotten from the clouds that were still trailing over our heads that afternoon — as the “meaningful” shape of a tornado.  And the evidence that she saw the triangle form as meaningful is that she asked WHY the tornado was that shape.

The question “why” only has meaning if a person wants to know the connection between a form and its cause.  And the “cause” or “reason” for form is almost always function.

If you look at the line of pictures above, again, you will see that understanding how tornadoes work, functionally — that they are a rotating vortex — makes sense of the wide variety of forms shown there.  Sometimes the clouds are way up high above the ground and the rotation’s diameter is narrow, so the tornado’s form is that of a long rope.  Sometimes the rotation’s diameter is so large that a tornado is wider than it is tall, and the form is then like a wedge that blots out much of the sky at the horizon.  When the clouds above blow along faster than the base of the thing moves, the tornado leans sideways, the part on the ground trailing the part at the cloud.  When condensation doesn’t happen around the vortex, you see debris flying around in a circle but not much else — sort of an “invisible” tornado.  And, of course, if the clouds and the ground are at a particular distance apart, and the diameter of the rotational part in the cloud is a certain proportional size, and the debris field around the base on the ground isn’t very big, and if you happen to be standing in just the right place with a certain point of view — then the tornado looks like a triangle.

Virga: sheets of falling rain, seen from a distance.

A cloud that happened to hang down, maybe like a rain virga, and was shaped like a triangle, that did not rotate and did not have updraft in the center of it, would not be a tornado.  It would not cause damage.  It wouldn’t be dangerous.  It might be an interesting phenomenon, but it would not be a tornado.  The form of a tornado is a product of its function.  Details of the specific situation, such as how high the clouds are and how wide the rotation diameter is, create variation in the form.  But a tornado is a function-based phenomenon.  Even the very oddest-looking tornadoes in the line of photos above is still a tornado because it functions as one.

The bottom line of form — the thing that produces form — is function.

So what does this have to do with horse biomechanics?  Remember, I said at the outset of this post that sometimes it’s hard for me to realize how far form and function are divorced from each other in people’s awareness.  I have the artist and the tornado to thank for bringing this to my attention the first time.  But now that I’m working to help people understand horse biomechanics, I discover that the separation of form from function in people’s minds is extremely common. And so is the focus on form, all by itself.

If meteorologists thought that tornadoes really were triangles, if they did not understand that how tornadoes function is the most important thing to understand, that form is merely an outward manifestation — almost a side-effect — of this critically significant function, we would not have radar warnings to tell us to take shelter.  The ONLY way people could know a tornado was in the area would be if a spotter happened to see it and see it from exactly the right “triangle” vantage point.  It is understanding tornado function that allows us to predict them, to identify them on radar, and to design special structural elements that help keep buildings from flying apart in rotating tornadic winds.

Horses have anatomical systems of bone, muscle, connective tissue, and nerves that function, together, in a range of very specific ways.  Certain patterns of horse anatomical function produce forms that we recognize, just as certain functional patterns of wind rotation produce the recognizable form of a tornado.  The parts of a horse’s body are connected to each other in complex ways.  When certain nerves fire, they cause certain muscles to contract, which causes specific movement of certain parts of the skeleton.  The end result of this chain of causes may be that the horse’s head rises from a neutral position.  If so, this is a side-effect of the entire functional chain.  The raising of the head is a result, not a cause.

Yet, what I have learned is that many horse people see that a horse someone has identified as being collected has an elevated head — and conclude that this form of “elevated head” is the cause of collection, that it is the actual functional mechanism of collection.  They therefore pull on the reins and on a horse’s mouth to raise its head and “pull it into a frame”, thinking this will functionally produce collection.  But functionally, it can’t.  Bodies don’t work that way.

He’s not about to jump off the cliff as a result of having raised his arms. Jumping may cause a person to raise their arms, but raising their arms does not, therefore, cause them to jump.

Human beings tend to put their arms up and out when they leap into the air.  But you can’t “make” a person jump by having them raise their arms.  It doesn’t “go that direction”, functionally.  If humans were trained to jump by aliens (E.T.s) who did not understand the functional mechanisms of jumping, by aliens who focused instead solely on the one aspect of form “arms raised”, then these aliens would try to train humans to jump by lifting their arms over their heads with ropes and pulleys.  Presumably the aliens would be frustrated and irate when no one jumped as a result.

It is a trainer’s responsibility to learn what the anatomical functions are, that produce particular forms such as collection.  This is absolutely what the great trainers of the last few centuries have done.  They may quibble about the details (scientists do too!), but they understand very well that form is not a cause but a result.  If a rider trains her or his own horse, then they have just picked up the trainer’s level of responsibility in this matter, whether they know it or not.  And because the responsibility exists, so does the power to harm a horse that is forced to move in a way that produces only a meaningless form, on the assumption that the rest of a functional sequence will somehow follow even though the real cause-and-effect line flows the opposite direction.

Given that bones and muscles are largely hidden by the horse’s skin, how is a rider or trainer to understand the functional mechanisms that produce the forms they desire in their horses?  There are plenty of books and articles on horse functional anatomy and biomechanics available, and this blog and my seminars are two small contributions to that field of knowledge. But any time you read one of those that tells you to focus on FORM as the most important part of anything, as the part that produces function . . . stop and ask yourself our riddle:  “When is a horse like a tornado?”  Because right at that moment you will have encountered the answer:  “A horse and a tornado are alike when the person thinking about them focuses on FORM rather than FUNCTION.”

By the way, it turned out the artist had not really registered either the circular rotation or upward movement we had witnessed.  Instead, while watching the spectacle, spellbound, she had reflected on the photographs of tornadoes she had seen.  This is what prompted her question.  When I pointed out the functional aspects of tornado shapes, she explained that it didn’t matter at all to her because, as an artist, she only cared about representing images of tornadoes on paper or canvas — not creating functional ones.  I strongly suspect that most horsepeople, to the contrary, do want a functional horse rather than 2-dimensional representations of one.  So although horses and tornadoes may be alike when people think about them the same form-based way, the people who do the thinking — horsepeople and artists — may be rather different.

Although Leonardo da Vinci might disagree with that. . .

(At left, a page from one of da Vinci’s notebooks, detailing one of his studies of dissected arm and shoulder structures.  Other Renaissance artists also carried out dissections, which they carefully drew, realizing that they had to understand the function of human bodies in order to render their forms realistically.)

Finding Balance

The slogan Jo (my business partner) and I use for our horse work is “Balance, Center, Connect.”  This is the logo we designed for the first horse program we ever ran, which was at that time part of the work in which our non-profit, Tapestry Institute, was engaged.  We coined the phrase to refer not only to our horses’ own best functional states, and to the states that allow us to have our best riding experiences, but also, purely and simply, to ourselves as human beings.

We all know it’s difficult for a person who’s not physically balanced to ride well.  They continually throw their horse off-balance with their own off-kilter weight (which produces the “eccentric load” I talk about in my biomechanics seminars), accidentally asymmetrical hands and feet, or body stiffness that translates itself right into the horse.  The same is true of being physically centered.  And of course we need just the right amount of physical connection with the horse we’re riding to communicate responsibly as well as effectively.

But emotional balance matters, too.  Who among us has not had a miserable time riding, fussing with our horse for being “difficult,” only to realize with a sudden pang of guilt that we went out to ride that day already angry or upset about something else?  An emotionally unbalanced state communicates itself to our horses just as freely as it does to the humans around us, who can at least use spoken words to ask us to “lighten up” or “take a walk to calm down” before dealing with, and upsetting, them further.

When it comes to understanding how horses move and support themselves and their riders, it’s also important to balance different types of knowledge.  But doing so is extremely difficult because of our culture’s deeply-embedded assumption that logic, reason, and mathematics are the most valid ways of understanding reality.  “Factual” information is seen as trumping any other type, “science” is seen as producing the most reliable facts, and information that is mathematical is seen as being the “best” type of science.  Here’s an example of the result of this type of worldview.

Hilary Clayton, Ph.D., at Michigan State University’s College of Veterinary Medicine, has carried out studies on the biomechanics of bits.  Clayton is a solid researcher who holds excellent credentials and has published a number of books.  But her work can be a bit daunting for many people to read.  Her biomechanics and physiology books, in particular, are ones I would personally select for my students to use if I was teaching a graduate course in biomechanics, but be reluctant to recommend as an easy-to-use resource for a rider who doesn’t want to get a graduate degree.  Yet Clayton gets her work “out there” in clinics and talks — and is frequently misunderstood by people who are looking for “facts”, particularly mathematical ones they can hang their hats on with pride of knowledge.

Clayton’s work on horse bits was summarized and reported in Horse Science News in an article titled “Myler Bits Act Differently on Horses.”  More than half of the three-paragraph summary was devoted to mathematical data, such as:  “The jointed snaffle and Boucher bits both averaged 3.3 centimetres (1.3 inches) away from the teeth, whereas the Myler snaffle lay just 2 cm from the premolars. The other two Myler bits were located even closer, at 1.3 cm from the premolar teeth.”  A reader studying this report is left with the comforting notion that “something important” has been learned about bits, particularly about the place in the mouth that myler bits sit compared to other bits, and that single-jointed snaffle construction and rein tension are somehow relevant factors.  At the same time, I think it would be difficult for most riders to apply any of the information presented.  I also think, from my years of doing public education with Americans who both respect and dislike science (thanks in large part to nasty grade- and high-school experiences) that most of the people who couldn’t make heads or tails out of what to do with this information would assume the problem was their own — that they didn’t know enough, or weren’t smart enough, to see at once how to apply it.

The trickier part of this is that I also know, from long experience, that there are people who do bitting clinics as part of their general horse business who, when they come across this numbers-filled article, will figure out a way to say that the figures support whatever view of bits they propound in their clinics.  If you think people don’t do that, just watch the labels on (and ads for) products in the grocery store the next time there’s big news about a scientific study linking a particular nutrient or compound to some aspect of staying healthy.  And it makes sense if you think about it — as long as the “facts” have been appropriately represented in the press to begin with.  And that, as the PLoS Medicine article I just linked to shows, is the rub, right there.

On the other hand, take a look at this article summarizing Clayton’s bit research at Horse Journal on the Equisearch website.  (That’s not a rhetorical statement.  I really recommend you read the material to which I’ve linked.) This article, titled “Dr. Hilary Clayton Offers Many Prescriptions for Bits,” has an entirely different theme:  “Dr. Hilary Clayton has been studying the way bits act on horses’ mouths for more than 20 years. But even after all those years of systematic research, she still says that ‘finding the right bit is more a matter of trial and error than a scientific process.'”  The italics are my addition, to highlight the part of this statement I find particularly meaningful.  The article then goes on to list some generalized findings that will come as a surprise to many horsepeople — one of which is that many horses prefer smaller-diameter to larger-diameter bits because their mouths are smaller than we think they are — and then quotes Clayton categorically stating that the rider has to figure out which bit their own horse is most comfortable using:  “‘So the size and the shape of the bit is individual to every horse, meaning you have to keep trying until you find a bit they’re comfortable with”.  This is repeated in the article’s last line, which concludes:  “. . . Clayton still believes that finding the right bit for your horse is a matter of simply trying different bits.”  Please notice that this research scientist is emphasizing the real value of experiential knowledge here, rather than “fact”-based knowledge, in two ways:  (1) the rider is to use a personal trial-and-error method to try different bits and see how each one works, and (2) the rider is to assess each bit tested by using their own individual perception of how comfortable their horse is with that bit in its mouth.

You don’t have to look far to find publications in which people who claim “horse expert” authority denigrate the very idea that horse “comfort” matters or that humans can assess a horse’s comfort.  Further, such “experts” claim to use science, of all things, to give authority to their denigratation of experiential modes of understanding and to support their own fact-based system of information as not only best but also the only reliable source of knowledge. This is what leaves horsepeople feeling stuck, unable to get themselves and their horses out of situations that don’t feel right.

Yet here is a highly-credentialed research scientist who’s emphasizing experiential learning, the significance of a horse’s comfort, and the reliable ability of a horse owner to tell if their horse is comfortable or not.  Given that the non-scientist “bit expert” who denigrates the horse owner’s experiential learning is claiming the authority of science (supposedly), then should not the actual scientist have the higher authority in this case?  If so, then the paradoxical situation is that it is the scientist who turns over the tables on what type of knowledge has real value, placing the final authority squarely in the hands of a rider and the responses of her horse.  And if that rider says, “But I don’t know about bits,” then look again at the article I linked to and you will see that it addresses this issue.  Clayton points out the salient factors that usually impact bit comfort, that we need to pay attention to, including how high or low in the mouth the bit rides, whether it’s single jointed or has a flat area over the tongue, whether it touches the roof of the mouth, and the importance of paying as much attention as possible to the size of the mouth cavity since it’s not directly comparable to the horse’s body size.  In other words, there are pieces of “factual information” she’s learned in 20 years of bit research, and she’s passing those on in order to give riders information about what to look for as we run our own tests.  She is teaching us what to look at, how to see.

So that then we can make our own decisions.

That’s what science is about.  It’s about learning what factors exist, since usually we aren’t aware of even a tenth of them in normal practice.  It’s about learning which factors that we never even thought of are really important to pay attention to.  And then it’s about learning how to integrate information about these factors into a much larger scheme of understanding the subject so that we can make personal decisions that are wise and informed.  This is real science — which, interestingly, is based on trial-and-error (which is called “experimentation”) and personal assessment of results (which are called “sense-data”) — the two specific methods Clayton recommends horsepeople use to select the right bit for their own personal horse.  Oddly enough, the fact-based, supposedly “science”-based system we find so often in the horse world, that tells us horse comfort is an illusion, that riders can’t possibly decide what’s best for their horse (but must hand over decisions to Experts), and that all horses in a certain discipline “must” use a particular bit because “we know” that bits work in such-and-such a way is actually not scientific at all.  And I am saying that as a scientist with a doctorate from a major university, who has participated in policy discussions about the nature of science and of communicating science to the public in formal and informal education at the highest levels possible in the US.

All this being the case, my goal for this blog and for my seminars, both, is to share what I know about horse biomechanics and horse movement to help people learn how to see their horses better.  I want to share information that helps riders see and appreciate the really astonishing power and subtlety of response that exists in a horse’s systems of adaptation to stress, and to learn what to look at when they assess how their horse is moving.  I want to help people better understand the basic biomechanical adaptations of their own human bodies, to feel how subtly but profoundly those operate, and then use that information to understand the operation of those same systems in their horses’ bodies.  And I want them to be able to use this information, even twenty or thirty years from now, with everything else they know about horses in general and their own horse in particular, to feel confident enough about their own authority to tell a trainer, when necessary:  “No.  I realize the method of moving you use on horses may work for many, but it’s not good for my horse.  Thank you for your efforts to date, but I am discontinuing his training with you.”

The problem with my original blog post on force, stress, and the hoof was that it focused on numbers.  It focused on calculations. It focused on apparent absolutes that really do not exist except in the most artificial situations imaginable (where, for example, a horse is literally not moving a muscle).  And in doing all these things, it took us all to exactly the place I don’t want to go.

The first time I took it down, it was because I thought about all this.  What I did was put it back up with a paragraph added near the beginning:  “I want to say at this point that calculating, or even measuring, force in a living body is extremely difficult — sometimes impossible — for practical reasons having to do with the incredibly responsive systems of animal support, balance, and locomotion, and the fact that contraction in even a single muscle is generally along a wave that makes its force vectors change rapidly and dramatically.  So the goal of this blog and the next is to look at things in just enough detail for you to get a working idea of the levels of load on horse hooves, and the sorts of things that impact those loads for better or worse.”

But the post still bothered me.  Because I knew very well that my disclaimer — which was the real point of all the horse biomechanics work I do — was going to be monumentally outweighed by the correct but almost meaningless calculations I had gone to such great lengths to explain, about force and stress in the hoof.  And finally I realized I have to go about explaining this a different way — one that focuses on the issues of subtlety and responsiveness in the horse’s living systems of adaptation.  One that leaves the numbers out unless there’s an essential reason for them, and then makes very certain to keep them in perspective.  One in which all the different ways of knowing about and understanding how horses move are in balance and connected.

I close with the same Calvin and Hobbes cartoon with which I opened my ill-fated post of hoof stress calculations, this time focusing your attention on all the different ways of knowing that Hobbes combines to be an effective tiger. The laws of physics and the principles of biology are important factors, but so are art and ethics.  All I can say is:  right on.

So now I’m in balance again, not focused all to one side of things with purely intellectual and mathematically-based knowledge.  And I’m centered once more, squarely in the framework of the goals I have for this blog, my seminars, and my life work in general.  The result, I hope, is that I’m better connected to you, the reader.

And NOW we can go on to consider force and stress in the hoof . . . this time, in a way that has a little more meaning, and meaning you can use.

See you next week.


This post was a featured blog entry on BarnMice, Jan. 2, 2013.

Hoof Structure

The amount of information available about horse hooves and their trimming, shoeing, barefooting, wrapping, booting, soaking, and “orthotic-ing” is mind-boggling.  So the first thing I want you to know in this post is that I’m not going to summarize all that or wade in to the “natural hoof care” debate or encourage you to purchase a product of some sort.  My goal in this post is the same as it is for the blog as a whole: to offer you a different point of view on a subject — one that doesn’t seem to be readily available otherwise — that is based in biomechanics and good, solid biology.  It will be your job to take what you learn here and figure out how you want to integrate it with what you already do.

This post will discuss specific aspects of the biology of hoof structure, and then the next post will consider functional aspects of those structures in terms of basic biomechanics.  In both posts, the place we’re heading is a consideration of the nature and size of the element called the “coffin bone” by horsepeople and the “terminal phalange” by anatomists, and how that element functions in the stress environment of a large animal’s hoof.

We’ll start by looking at what bones are in a horse’s legs and feet.  These bones have names as well as “definitions” based on where they’re located in the body and what other bones they connect to on the ends.  For instance, animals have a lower jaw bone called the mandible.  In mammals, the mandible is entirely mde of a bone called the dentary, which bears teeth on its upper surface (if the animal has teeth in its lower jaw at all, which some do not).  There is a right dentary bone and a left dentary bone, one on each side of the animal’s lower jaw, and they join each other in the middle at the front (to form what we would consider the animal’s “chin”).  The two halves are “sutured” there (that is the anatomical term) by a joint that is fixed or immovable and that looks like a wavy line of back-and-forthing such as might be done by a needle and thread.  As the animal ages, this line disappears and there seems to be only one bone instead of two.  On the back end of each mammal’s dentary bone there is a process that sticks upward, that makes a fairly high crest and that has a lower piece sticking back with a roller joint on it.  When the lower jaw is put in proper life position against the skull, this roller joint articulates or fits against a socket in the skull, and the jaw rolls to open or close the mouth at this joint.  The high crest projects up through a part of the skull that sticks out from the rest of the bone as a big arch.  In life, it can be seen that strong jaw muscles attach to both the crest of the dentary bone and that arch on the skull.  These muscles help to pull the jaws together so the teeth can chew food.  Here is what the dentary looks like in a horse, when it is not attached to the skull.

The picture below (left) shows you how the dentary bones look in position, articulated with the skull.  You can see the crest goes through an arch on the skull and that the roller joint articulates with or fits up against a part of the skull that is shaped to receive it.  The dentary in this picture is the white (uncolored) bone.  The lower teeth are hidden by the upper teeth, which “lap” around them to the outside as this is drawn.

The skull to the right of the horse, above, is that of a human.  It shows the human dentary bone and the way it fits to its skull, for comparison.  I have colored the dentary a light bluish-purple.  The point is to notice that the basic shape, position, and relationship to the bones around it are the same for the human dentary bone as in the horse.  That’s why we consider both bones to be dentary bones, is that they meet the same “criteria” of definition for that bone.  The dentary of the horse is therefore said to be homologous to the dentary of humans. It should be added that homologous structures may be seen to develop from the same embryonic tissues during development of different animals.  So the similarity of structure that we call homologous reflects a real commonality of genetic origin and development.

Comparative anatomy gives us powerful tools for understanding animal structures.  That’s probably more true for the hoof than for just about any other structure, because we all know how vitally important a horse’s hoof is.  “No hoof, no horse” is an adage that’s been around about as long as people have been riding and working horses.  And it turns out that the hoof is an astonishingly “little” bone.

Here is a horse skeleton with the bones of its front leg colored in a specific way.  The circle I’ve drawn is around the bone horsepeople call the cannon bone, to serve as a place-marker with which you’re familiar.  I’m not going to worry here about what other names horsepeople have coined for different parts of a horse’s limb anatomy, because that will actually confuse matters.  I’m going to use terms that tell us about the homologies of these structures instead. Next to the horse skeleton is the skeleton of a human arm.  I have colored the bones there so they correlate to their homologues in the horse skeleton.  As we run through these bones, you can use your own arm and shoulder to help you learn the structures experientially.

At the top of the of the arm, the first good-sized bone that moves the arm in a mammal, is the scapula or shoulder blade bone.  It’s colored pale turquoise here.  In a horse, the scapula lies beneath (and gives the sloping ridge-shape to) the withers.  In a human, the scapula is “down behind” our arm in our back because of the way our chest is flattened out side to side.  There is a bone called the clavicle or collar bone in humans that is shown in white on the diagram above, that is not present in the horse.  Then the next main bone in the sequence is the humerus bone.  We looked at the humerus bone already in our discussion of the trotting gait in horses, and it’s colored in red on the diagram.  It’s also in red on the human skeleton.  In you, the humerus is inside your upper arm.  (You’ll have to disregard the horse’s back leg here, on which I previously colored the femur red as well for a previous blog.  The horse’s back leg is homologous to a human’s leg, too, but we are going to focus on the foreleg and arm as our example for this blog.)

Beneath (or “outward from”) the humerus there are two bones, side by side:  the ulna and the radius.  Here, I have colored the ulna a light green and the radius yellow.  In humans (and many other mammals), the two bones are totally separated their entire length.  They twist back and forth across one another when we rotate our forearms to turn our palms up or palms down.  (If you sit with your right arm bent at the elbow, with your right hand just above your lap, you can move your arm in a way that allows you to feel these two bones.  Put the fingers of your left hand across your right arm, about halfway between the inside of your elbow and your wrist.  Press down firmly.  Then, without moving your upper arm, simply twist your wrist to rotate the palm of your right hand so it faces the floor, then faces the ceiling again. (Your right thumb will face left when your hand is palm-down, and right when your palm is face-up.)  The fingers of your left hand should feel the radius cross over the top of the ulna when you do this.  The ulna is the longer of the two bones, and the back end of it “sticks out” to form our elbow.

Horses have an ulna and radius, too, but theirs are fused together not too far below the elbow area.  (The next time you saddle your horse, take a good look at the part of the horse’s arm just in front of the cinch or girth.  You will see a very obvious elbow there.)  It’s hard to see what they look like in the skeleton above, so here’s a closer picture of just those two bones in a horse.  I colored the ulna light green and the radius yellow.  You can see the dark line between them near the top of the radius, and then you can see that the ulna fuses to, and essentially becomes one with, the radius farther down the shaft. This is because the separate ulna and radius allow the hand to be twisted around the long axis of the leg — as is so in us — and that would be a really bad way for a horse’s leg to move.  Can you imagine what would happen if a horse was running at 30 miles an hour and suddenly twisted its front hoof on its leg?  So there is an adaptation of this structure that keeps the twisting motion from taking place.  The radius and ulna are “locked” down.

Beneath the radius and ulna are the wrist bones, or carpals.  In the big skeleton, those are not even drawn in, they are of such little consequence to many horsepeople learning anatomy.  But of course, those bones are extremely important and you sometimes hear about one or more of them being injured in a performance horse.  Since we’re heading for the hoof, though, we’re going to skip the carpals for now and head on downward.  So the carpals are simply white on the human skeleton as well.

Beneath the carpals are the finger bones.  The first of these is a long metacarpal bone that is actually positioned inside the fleshy part of the hand (where the palm is).  Then, at the end of each metacarpal, there is a series of three little bones, each called a phalange.  There are three phalanges on each finger except the thumb, which has only two phalange bones.  If you take a look at your hand, you will see all this.  On the human skeleton, I have colored the metacarpal a dark blue, the first phalange dark red, the second dark green, and the last orange or dark gold.  However, I have only colored the bones of the middle finger — because that is the finger homologous to the hoof bones of a horse.

Look at the colors of the bones in the skeleton above, showing the horse hoof.  You will see that the cannon bone is actually a metacarpal.  And the bones that make up the pastern and the hoof are phalanges. Here is a diagram that shows you the end of this sequence a little more clearly.  It’s a photograph of a horse hoof that was injected with plasticine so it could be sectioned cleanly and show you the structures.  On the left is an image without any modification, and on the right is the same image with the bones colored so they correspond to the key I’ve just run through. (The diagram, from Wikimedia commons, is labelled in German.)

What should blow you completely out of any sense of complacency about your horse’s abilities, here, is realizing how very tiny the bone is that’s inside your horse’s hoof.  I mean, LOOK at it!  Here’s a nice shot of this coffin bone from a horse care website, that happens to have the edge of a person’s thumb and thumbnail in it, for scale.  Take a look at just how small this bone really is.  And if you consider the fact that the “hoof bone” or “coffin bone” is, in fact, a terminal phalange — the last tiny bone of a single finger — the fact that it bears so much weight, running at high speeds is nothing short of astonishing.

We are impressed, and rightfully so, by ballet dancers who leap and pivot en pointe, with their feet positioned so that their weight is borne only on the tips of the toes.  Depending on the gender of the dancer, they may weight perhaps 80 to 150 pounds a person.  What you can see here is that horses are also en pointe, minus the ballet slippers, but carrying closer to 1000 or 1200 pounds when they run, jump, and spin on those toe tips.  It takes nothing away from human ballerinas, but I think it certainly adds to our appreciation of horses.

Or at least, I hope it will after we consider the consequences this has for the stresses (force per unit area) in the bones of horses’ feet.  Coming up, next time . . .


This post was a featured blog entry on BarnMice, Dec. 1, 2012.


Moving Horses

You can take the title of this blog as meaning either or both of two things:  horses that are moving (in which case the word “moving” is an adjective), or the things a person does to move a horse (in which case the word “moving” is a gerund).  The two things are related, which will turn out to be the theme of this blog.

This entry is the joint product of two people:  myself as the anatomist and biomechanics scientist, and my business partner Jo Belasco as professional trainer. Jo and I have worked on what might be called “applied horse biomechanics” together for over ten years now, and although I wrote the words you see here, they only came into existence after lengthy conversations with her and discussion about this very post.

The impetus for writing this entry was that a horse friend wrote me in response to my post about the walk, saying that although he’s heard many trainers insist that a horse cannot move the leg it’s standing on, and that cues to move a specific foot need to be provided when that foot is off the ground, he doesn’t see how this can be so.  “If it were true,” he wrote, “there would be no way to start a horse from the stop.  Maybe the ‘rein or seat’ qualifiers are important here, but I had a horse that was so forward he would move if you simply relaxed the reins. . . All with no reference to influence with the foot on or off the ground.”

My friend’s comments made me think about the glib way we all short-cut biology to smoosh terms around in ways that give them meaning they were never meant to have, and the impact such short-cuts have on how we think about and deal with horses.  So here’s some additional thought about the walk and the training practice of learning to cue a horse’s foot when it’s off the ground.

When people say you can’t move a horse’s foot unless it’s not on the ground at the time, they are really making a short-cut statement.  The real statement should be:  “If you cue a horse to move its foot when that foot is bearing weight at the time, the horse won’t be able to respond immediately and/or in the way you’ve asked.  And because horses move quickly, even at a walk, if you cue them any later than the moment you feel their foot come up, you will be too late.  They will have put their foot back on the ground before they have a chance to respond.  Furthermore, you want to cue them early enough that their foot is not only still in the air, but able to be redirected to come down somewhere else than where it would have gone otherwise.”  Yes, that’s a lot to say, but of course it’s why we speak in a short-cut.

Let’s consider, first, where this idea comes from, which is ostensibly the nature of the step cycle.  A step cycle is the complete range of motion made by a limb from the time it leaves the ground to begin a step, through the time it advances and comes down again to the ground and bears weight, until it leaves the ground again to take a new step.  The sequence of still images below shows one complete step cycle of the left hind limb of the same horse that was pictured in the walking blog I posted on October 12.  The screen grabs are from the same slow-motion video I used there.  The blue arrow I’ve added to the first frame shows the foot coming up off the ground to begin the step cycle.  It’s a little hard to see that the heel is up in that image because of the way I reduced it to fit on the page.  But the heel is up off the ground where the blue arrow is.

1. Left hind foot comes up from the ground as right front starts to come down and be placed.

2. Left hind foot is clearly no longer supporting weight. Weight is now on the other 3 legs.

3. Left hind foot is now being brought forward again, though toe is neary dragging on the ground in this horse.

4. Left rear continues to come forward, now passing in front of the right rear foot (which remains in place, here).

5. Left rear moves a lot farther forward and approaches the ground

6. Left rear foot is placed on the ground, well in front of right rear foot.

7. Left rear foot is bearing weight as right rear foot now comes up. (Left front is coming down, so notice that weight is presently on only two feet.)

8. Left rear foot is still weight-bearing, but right rear foot is now being brought in front of it. Weight is on 3 feet at this time.

9. Left rear foot still weight-bearing but body is now being thrust in front of that foot as right rear foot approaches the ground.

10. Left rear foot is now behind the horse but still fully flat on the ground.

11. As horse prepares to lower right front foot to the ground, weight begins to shift off of left hind foot, though it is still on the ground.

12. Left rear foot begins to come up from the ground as right front foot touches down. This is just barely past the same part of the step cycle shown in picture 1.

You will notice several things in this sequence, if you look closely, all of which give you a little better understanding of the walk.  First, the horse is moving its body forward (the whole point of walking) by pushing the foot back against the ground during part of the step cycle.  So the position of the foot we’re watching changes with respect to where the horse is.  When the foot is coming up off the ground in the first frame, it looks to be about 4 feet to our right of the vertical wooden post, which is at that time behind the middle of the horse’s neck.  Mid-way through the step cycle, in frames 6 – 9, the horse’s left hind foot is fully on the ground and supporting weight.  It has been brought forward about 2 feet, so now it is only about 2 feet to the right of that post.  At this point, the post is behind the horse’s withers (in 6) and then the end of the back (9).  By the time we get to the last frame, where this back left foot comes up off the ground again, it’s still about 2 feet to the right of the post — but now the horse has advanced so far forward that the post is behind its rump.

Many trainers say a rider could ask this horse to move that back left foot in about frames 1 through 3, when it’s come up off the ground and has not yet been set back down.  So they teach riders “feel” of the feet so they can tell when that particular foot is in the position shown in frames 1 through 3 — and that’s when they cue the horse to set that foot down someplace other than they were about to put it.  These trainers believe that if the horse is asked to redirect that foot between frames 6 and 11, the horse won’t be able to respond even if it wants to because it is standing on that foot and therefore unable to move it (unless it breaks its gait by hitching or stumbling). In the case where you are asking a loping or cantering horse to change its lead, there is even the possibility that it will respond on one end (that can respond at that moment) but not the other (which can’t), with the result that it cross-leads if you ask for a change of lead while the back foot that needs to move is on the ground.

Because of my biological background, I was actually suspicious of this idea for quite a while.  The reason is that neurological researchers spend a lot of time considering what they call Reaction Time (or “RT”, because of course it has to have a catchier and geekier name than just “Reaction Time” if you study it in your lab).  To get an idea of the level of discussion about how long it takes a body part to respond to a stimulus, and the kinds of factors that impact this response, here are abstracts of a couple of scientific papers on the subject from the National Academies of Science and the American Psychological Association.  What you will see, besides the designation “RT” and other jargon that might make you reach for a pain reliever, is that moving a foot in response to a cue is not a simple matter of stimulus-response.  There is a lot that affects how quickly a motor response is expressed when any animal hears, sees, or feels something — which is to say that how quickly a horse moves a foot in response to the touch of a heel or rein is not a simple matter of picking the “one right part” of the step cycle to offer the cue (stimulus).

Researchers in RT want to know how quickly a human being can respond to switch off power to an engine if an alarm sounds, for instance, so most of the work on Reaction Time is on human beings. If you wade through those abstracts, you will see that their work suggests that a person’s reaction time can vary according to things like practice, the kind of stimulus presented, how many response options exist (in other words, do you have to decide whether to flip the lever or push the button, or is there only one choice), the nature of the on-going task or activity, and how much attention is being paid to specific parts of the environment.  Just to show you how important these factors are, visualize for a moment the memory of an experience I’m sure you’ve had — a sudden loud noise or sharp motion startles a horse, which proceeds to leap straight up into the air with all four feet at once.  It might have had all its feet on the ground a split second before, but the nature of these other factors changed its “normal” Reaction Time dramatically.

Most of us hope we don’t generate that kind of reaction in our horses.  The point is that when we talk about “when our horse can move a foot in response to our cue,” we are actually talking about Reaction Time whether we realize it or not.  And, given that we are, it’s a much more complex phenomenon than we imagine.  A lot of things, including training, can impact how quickly our horse responds to a stimulus-cue.  Furthermore, even though the Reaction Time for a foot placed squarely on the ground may be longer than if it was in the air when we cue it, that Reaction Time still exists.  A foot that is on the ground when we cue it can and will (if the horse chooses) react to our cue when it come up off the ground a few seconds later.

In the worst case scenario, the horse might react to the cue with a different foot and get a bit tangled up, which is how it’s said that cross-leading can happen by accident, or the delay of responding with the correct foot might lead to a bit of ungainly movement.  But most of us who ask at the “wrong” or “sub-optimal” time don’t usually wind up with our horses tripping all over themselves.  Usually what we get is movement in the direction we want, just a bit later than we asked for it — which is actually usually ok with us.  Few of us are engaged in activities that require our horse to move a particular foot at a particular time in order to, say, keep from falling into a hole in the ground.  So a little-bit-late response is just fine.

Or at least, this is what I thought until I saw a Tom Dorrance video about learning to move a horse’s feet individually while riding it.  In this particular video, Tom Dorrance worked with some riders and their horses and a pattern of tires laid on the ground, to help the humans figure out how to tell where the horse’s feet were at all times and respond to their horse and the tires.  The point of the exercise was to develop feel.  The demonstration of feel was that the rider could move a horse’s foot exactly and precisely at the time desired, to the place desired.  So there was discussion in the video about feeling when the foot came up off the ground and giving the cue then, as is standard in this type of training.  The result was astounding and unexpected.  Remember, I was pretty jaundiced about the idea that a cue has to be tied so closely to the step cycle because I had a healthy respect for the complexity of Reaction Time.  But every rider who engaged in this exercise, and learned how to feel where the feet were and to cue them at the “appropriate” times developed an incredibly light and responsive riding relationship to the horse s/he was on.

Jo uses some of Tom Dorrance’s methods when she gives riding instruction, and she’s the one who developed the closed-eyes on a bareback horse walking exercise I described in my previous post.  Sure enough, she found — and I saw it was so — that when people learned to feel their horse’s feet coming up off the ground and paid attention to it enough to cue them “at the right time,” they got light and responsive movement from the horse.  I also saw other trainers working on teaching the same “learn to feel when the foot comes up and cue it then” method in clinics in a variety of riding disciplines, and again I saw that when riders began to develop feel of their horse’s foot positions, a light and responsive relationship blossomed into existence.  The uniformity of this response shocked and amazed me, especially given the huge variation in different trainers’ means of explaining and teaching the concept.  But as long as the rider finally learned to feel the horse’s feet, the response materialized.  So clearly something important was going on.  But what?

Remember that we know Reaction Time is not solely or even primarily dependent on the timing of the stimulus or cue, but instead a complex phenomenon.  So we have an “effect” here, which is a light and responsive horse, the “cause” of which cannot be, biologically, simply applying the stimulus at precisely the right time.  To find the actual cause, we must consider what else all these experiences have in common.  And what they have in common is this:  the human learns to feel where the horse’s feet are all the time, and learns it so well that a cue can be offered at one particular point in the step cycle of one particular leg.  Notice which words are in bold and italics.  It’s about what the human learns.

A human who learns to feel where his or her horse’s feet are is thinking about, and even physically connected with, the horse.  That human’s mind is no longer inside their own ego and their own intention — at least for a while.  Instead, they are focusing on the horse.  They are feeling the horse, quite literally.  And Jo and I both suspect, very deeply, that what happens is that this change in focus and concentration allows the horse and rider to communicate simply and effectively in an entirely different way than the one we usually think of as “stimulus-response.”  Which means, of course, that Reaction Time is irrelevant.  What matters is simply the development of feel.  And an exercise in which you learn where your horse’s feet are — with such precision that you can cue one at one particular place in the step cycle — will teach you that.  But the exercise is not about cuing the horse.  It’s about teaching the human to feel.

If you read Tom Dorrance, Bill Dorrance, or Ray Hunt you will see that this is pretty darned close to the way they talk about “feel”.  And given that they coined the concept, at least in contemporary equine society, that’s enough for me to take it as a “good fit” to the only explanation I can see for what happens in these riding exercise — given that the neurobiological “reason” usually given (Reaction Time) is actually not valid.  Did Tom Dorrance know this when he used a line of tires to teach a rider how to tell where his horse’s feet were, and how to move each foot at just the right time?  Was he actually and simply trying to teach “feel” in a reliable way?  Yes, I think he was.

In my walking blog, when I suggested ways a person could develop feel of their horse’s walking foot positions, my thought was that I’d give lip service to the “reason” this is usually said to be a good thing to do:  Reaction Time, or “you can’t move a foot that’s not off the ground.”  It was, after all, good enough for Tom Dorrance in that clinic I saw in a video.  But my real thought was that anyone who did that exercise would develop proprioceptive awareness of the horse they were sitting on.  And I do believe, after all I’ve seen and after the training work Jo has done to explore this, that if you do this exercise you will develop your sense of “feel” and, as a result, start to develop a relationship of light responsiveness between you and your horse.

If it works better for you to skip all the talk about “feel” and use the short-cut of thinking that you can’t move a foot that’s on the ground, that’s fine.  You will still learn where your horse’s feet are and when to cue a foot to move.  And that will get you light and responsive movement from your horse.  But you’ll need to pretend you don’t know about the complexities of Reaction Time if you do that — which is ok by me.  The complexities of the natural world get abridged in common understanding all the time, largely for the reason of generating actions that have simple and predictable outcomes that seem to be based in science.  But, as is usually the case in all such situations, understanding the science a little better actually takes you to a place you might not expect to wind up.

So if your horse already knows how to “go” and all you have to do is relax the reins, you’re in good shape in lots of ways.  But an exercise that teaches you to feel where your horse’s feet are, well enough that you can cue one foot at one particular place in the step cycle, will still give you something new that’s worth developing:  feel.  Horses already know how to walk, after all.  It’s we humans who have to learn how to go along for the ride without messing them up.


This post was a featured blog entry on BarnMice, Nov. 22, 2012.


Learning How Horses Walk

Sometimes the best way to understand how your horse moves is to mindfully experience how your own body moves.  This is called experiential learning.  When I used to teach comparative anatomy and functional anatomy in the university, I always told my students that the number one tool we all have to understand how animals move is our own bodies.  See if you don’t discover something really cool about horse movement by trying this exercise in experiential learning.

What you need to do is read the next four paragraphs (down to the break in the text), and then set your computer aside and get down on the floor on your hands and knees.  Yes, really.  Don’t just think about it, and don’t ask someone else (like your teenager) to do it so you can watch them.  You need to experience this for it to have the substantial learning impact it can have.

Get on your hands and knees, supporting yourself.  In other words, you don’t want to crawl like you’re scooting under barbed wire.  War games are next week.  (OK, not really.  But don’t scoot.)  Then just crawl across the floor as far as you can without hitting the furniture.  Don’t think about it;  just do it.

Once you’ve done that, and have your rhythm established, turn around and go back the other way, still crawling, but this time just pay attention to — but do not try to control — the order in which your hands and knees hit the floor.  I suggest you choose your left knee to start with as you make mental notes, and that you then notice what hits the floor next after your left knee, then next after that, and so on.  Do it several times so that you have a good idea of the pattern that exists when you crawl.  You can even stop and jot that pattern down.

Now go crawl.  :-)  I will skip some lines here so you can’t easily see what I write next, and can instead scroll down to it after you do the crawling exercise.







Unless something really interesting has happened (and bodies are interesting things, that surprise us sometimes), your order of motion was left knee, then left hand, then right knee, then right hand.  Of course, if you started by paying attention to the right hand coming down first, then the sequence would be right hand, left knee, left hand, right knee, right hand, and so on.  But the sequence is still identical.  It is that you put down the back “leg” (knee) on one side, and this is followed by putting down the front “leg” (hand) of that same side, and then you put down the back leg of the other side, which is then followed by the front leg of that other side.

Note:  It is very important to realize that the sequence is always the same, but that it will at first look different if you “start” with a different foot.  Each time a front foot comes down and hits the ground, the next foot that comes forward will be the hind foot of the opposite side.  But this is then followed by the forefoot on the same side.

Here’s what it looks like in a walking horse, in slow motion.  These images are stills edited from a video by British videographer “Mike Snail”, who posts his work series at Youtube under “Slow Motion Connection.”  I left in the time stamp information so you can see the sequence of things.


Starting with the left hind foot touching the ground…





Then the left front foot touches the ground…





Then the right hind comes forward and strikes the ground…





And finally the right front foot strikes the ground.




The entire clip is at youtube, here.  I strongly urge you to watch it, paying close attention to the sequence in which the feet strike the ground.

Now of course the point of all this is to go back and compare the horse’s sequence of limb movements at the walk to your own sequence of limb movements at a crawl.  They are identical:  left rear to left fore to right rear to right fore.  And they are identical to crawling in a human baby as well.  It is thought that this similarity is due to neurological homology — that the firing mechanisms that activate the limb muscles in that particular pattern are literally the same in both horses and humans.  In fact, Susan Patrick and two other researchers published a paper in the Journal of Neurophysiology in 2008 suggesting the structural/ functional pattern of the nerves that activate crawling and walking is so conservative that it’s the same in almost all quadrupeds — which is to say, in every animal with four legs.  (Note:  In biology, “conservative” means it has not changed evolutionarily.  It has remained the same over vast spans of time during which other structures have evolved and changed.  For more discussion of homology in gaits, see the previous blog post.)

What does this mean for you, as a horseperson who wants a better experience with your horse?  It means you have an inborn mechanism that allows you to understand where your horse’s feet are.  You have probably been told by at least one trainer, on a DVD if nothing else, how important it is to know where your horse’s feet are as it moves.  (That’s because it’s only really possible to move a foot with rein or seat if that foot is off the ground at the time, not supporting the horse’s weight.  You can’t move a foot someone is standing on.)  And if so, you’ve probably also been told one or more complicated ways to learn how to tell where your horse’s feet are.  But, as long as you’re willing to use your experiential knowledge, you’ve got all the tools you need right inside your own body.

Here’s a suggestion:  crawl around some more.  Get a good “feel” for your own body.  (Yes, I am suggesting that good “feel” for your horse begins with good “feel” of yourself.)  Then go out to your horse and ask someone to hold its lead line for you, and just halter it.  Then do one of two things: (1) get on your horse with its normal saddle, but place your hands on the withers right in front of the saddle, as far down the slope as you can in that position, or (better yet!) (2) get up on your horse bareback and lay your hands on the withers on each side, on the sloping area.  Remember that if a friend is holding your horse’s lead line, you don’t need to worry about holding the reins. Then close your eyes and pause, for a moment, to remember — as viscerally as you can — how it felt to crawl.  Fix that in your mind.  You can even let your legs and arms twitch a little bit as you remember their motion.

Then have your friend slowly lead your horse forward at a walk.

What you want to do here is focus on the similarity between the four feet your horse is moving and the pattern of your own limb motion when you crawled.  If you can let those two “walking feelings” overlap in your mind and in your body-awareness, you will suddenly have very strong “feel” for your horse’s feet.  And although at first you will be focused on when each foot hits the ground, the awareness will grow to the point that if you just turn your mind a little bit, you will know when each foot comes up off the ground to swing forward.

If it helps, particularly if you are on your horse bareback, you can lean forward so that you are oriented with your back more parallel to your horse’s back when you do this, which will overlap your fore and hind limbs more completely with your horse’s fore and hind limbs.

Either way, with a saddle or without, this exercise allows you to use your own body’s proprioceptive senses to feel your horse.  Your horse, in other words, becomes an extension of your own body.

And how cool is that?

Many thanks to my business partner Jo Belasco for the work she’s done with bareback riders who have their eyes closed as they learn to feel a horse’s feet at a walk.


This post was a featured blog entry on BarnMice, Nov. 19, 2012.


Gaits in Horses and Humans

In a very interesting conversation with a trainer whose observations are consistently brilliant, I realized that it’s hard for riders to see the similarities between human and horse gaits.  This is because the vertical position of a human’s torso, due to our being bipedal, changes the orientation of the arms or forelimbs, thereby obscuring their motion.  So I thought it might be useful and interesting to compare the motions of humans and horses, anatomically.

First, here is a horse in a trot.  If you ride, you are familiar with this gait in which the legs on one side of the body either come together beneath the midline at the same time or extend away from the midline at the same time.  In this case, the left fore limb is pulled behind its neutral position, and the left hind limb is moved forward or ahead of its neutral position. The neutral position of the uppermost limb bones is important to understand in this case.  So let’s look at a horse skeleton very quickly, to see what’s happening to make the limbs look this way.

In this horse skeleton, the animal is simply standing, not moving.  So the limbs are said to be in a neutral position because the horse isn’t going anywhere right now.  I have colored two bones red.  The one in the fore limb is called the humerus.  It articulates with the scapula at the top — and you know the scapula because it underlies the withers.  At the bottom, the humerus forms part of the horse’s elbow, just in front of where you put the cinch or girth.  Most of the humerus bone is not easy to see when you look at a horse, because it is so closely bound into the chest that we just don’t notice it.  But it’s there, and you can see its approximate position marked by a red line in the diagram of the trotting horse, below, that I have modified to show you where these crucial bones are.

I have also drawn a little turquoise arrow to show you the direction the humerus has moved (from the neutral position) to get to where you see it, in this photo of the trotting horse.  You may wonder, “If that’s where it is when it’s pulled backwards, how far forward does it go?”  You can tell by looking closely at the front of the horse in the picture.  You can see where its left elbow is;  now look at its right forelimb and imagine about where the right elbow is.  That elbow is a lot farther forward, and it’s because the humerus of the right leg is oriented about as far forward of its neutral position as it can get.  Horse humerus bones are not able to reach out as far as human humerus bones can.  But they do move, and you can see how much by comparing the positions of the two elbows on this horse.

Now let’s look at the back leg, comparing it to the skeleton above just as we did with the front leg.  Remember there is a bone colored red on the back leg as well, and that’s the femur.  I have marked the position of the femur with a red line in the trotting horse diagram, too, and also put in a small turquoise arrow to show you the direction it has moved (from the neutral or standing position) to get to where it is now.  If you look at the skeleton one more time, with the legs straight down as the horse is simply standing, you can see that the fore limb has moved behind that position, and the hind limb has moved ahead of that position.

So take a moment to familiarize yourself with the positions of the horse’s upper limb bones in a trot, and then let’s look at a human being jogging.

Here is a photograph of a jogging human being.  To many people, this does not look like the trot in the horse that we just saw.  But that’s only because your eye is tricked by the human’s vertical torso.  Imagine the person standing in a neutral position, not going anywhere.  The legs would be straight under the body, and the arms would be hanging straight down.  Now look at the left arm and leg, facing the camera.  Where is the left arm, with respect to the neutral position?  It’s behind it.  It has been drawn backwards.  And where is the left leg, with respect to the neutral position?  It is in front of it. It has been drawn forwards.  Does this remind you of anything we just saw?

Here is the same image, drawn and labeled as I did the trotting horse.  Compare the two labeled images, particularly the motion arrows of the humerus and femur bones in the human and the horse.  This still might look to you like it’s not the same thing, in which case it might help to turn the woman in the picture so that her torso is level, like the horse’s torso is, and then put her arms and legs back in place.  I cut the picture up and put it back together to help you see what this might look like, and it’s below — with my apologies for the rather Frankenstein’s monster effect of the cutting-and-pasting!

Her right arm, away from the camera, looks a bit disconnected here because of course it would be more visible if she wasn’t standing upright.  (When she is upright, her right humerus is partially hidden by her chest.)  But pay particular attention here to her left arm and her left leg.  The humerus of her left arm is drawn back, and the femur of her left leg is forward.  This is exactly the positions we see in the left limbs of the trotting horse in the first picture I posted on this blog.  And that is no coincidence.

Humans “trot” when they jog or run.  This is not metaphor, but actual homology.  Homology is an anatomical term meaning that something is similar because of an underlying commonality.  In this case, there are structures that are the same in both horses and humans — the humerus bone and the femur bone, for instance.  (Both articulate to the same bones at both ends, in both animals, and both are derived from the same types of embryonic tissues.)  The muscles are largely the same as well, and these are the muscles that move the humerus backwards and forwards, or move the femur backwards and forwards.  But, even more importantly when it comes to discussion of gaits, there are neurological commonalities as well.

Muscles contract to move bones when they are stimulated by nerve impulses sent by the brain.  Different patterns of limb movement that are highly stylized and predictable — like the trot — are created by very specific patterns of nerve firings on both sides of the front and hind limbs.  These firings must be coordinated very precisely for the animal to move properly without losing its balance.  For instance, simply to move the humerus backwards requires that a number of muscles fire in a very specific sequence and also that a number of arm muscles do not fire at all!  When you think about this having to happen on all four limbs simultaneously, you can begin to get an idea of the complexity and precision of neural firing patterns that generate movement in a certain gait.  Neural firing patterns — the actual placement of the nerves as well as the systems that regulate the patterns of firing in the brain — are very conservative, meaning they are much more similar between different animals than we might think they would be.  So even though a horse and a human look very different to our eyes, they both have a humerus bone and a femur bone — and the pattern of neural firing that produces a trot is not just similar, it’s nearly identical!

In my next post, I will talk about the walking gait in horses and humans.

(Note:  If you wonder why the woman’s lower forearm and hand are drawn up so close to her body rather than being extended on back and down as in the horse, it’s because she is not putting weight on her hand as she runs, as the horse must do.  Joggers are commonly taught to flex their elbows and “tuck” their forearms and hands close to their bodies to reduce drag and make running more efficient.  One reason we pay such close attention to the humerus and femur to understand gait is that they are under the closest neurological control and so show us the pattern most clearly.  Runners who try to run without at least letting their humeri swing as shown here generally find they cannot do much more than hobble — because the neural firing pattern is so tight that the femur needs the humerus to move in a trot in order for it to move in a trot;  the two are literally connected by the neural firing patternA person can learn to move only the femur bones to jog, but the firing patterns of the nerves are demonstrably very, very different — and not the “normal” pattern typical of a trot, even in the muscles around the femur.  This is why so much physical therapy is necessary to help people re-learn how to move if they suffer injuries that interfere with the normal firing patterns in any way.)


This post was a featured blog entry on BarnMice, Nov. 11, 2012.


Understanding the Horse

It seems like such a straight-forward title, “Understanding the Horse.”  Yet if it was easy to do, we wouldn’t have a book, video, clinic, and training industry that’s worth billions of dollars annually.

Two aspects of understanding the horse are represented by the seminars I offer via this website:  how horses stand and move, and how horses relate to humans through story.  While these may seem like two very different things, they are really deeply connected.  Consider, as just one example, the fact that apparently one universal symbolic meaning of horses is “rapid forward movement.”  It is for this reason, the psychologist Carl Jung pointed out, that horses are depicted in the iconography of “Knights” in the Tarot deck — developed at least as long ago as the 14th Century in Europe — to signify symbolically that an issue being asked about will move forward rapidly. So the rapid speed at which horses can move is symbolically a very deep part of the human psyche.

Biomechanics is a field of study that allows us to explore and understand how and why, anatomically, horses are able to move this way.  Study of the bones and muscles, as well as other soft tissues, and of their material properties and orientations allows us to appreciate how these animals can run at a speed of 30 miles an hour while carrying a second animal, one that may weigh as much as a quarter of its own body weight, on its back.  If you have ever carried a toddler on your back, and particularly if you’ve tried to jog or run with that child in place, you’ve got an idea of the specialized structures that must be in place for a horse to do this successfully.

Because I am a scientist trained in biomechanics, I have a solid understanding of the adaptations that allow horses to run at high speeds while carrying people on their backs.  And because I worked for many years in the field of interdisciplinary scholarship that integrates science with art, philosophy, spirituality, story, and culture, I have a good grasp of the ways that horses can be understood by looking at the roles they play in art, movies, books, and other expressions of culture.  And because I am a Choctaw Indian woman, such integration of knowledge is fundamental to the way I see and experience the world.  In the years that I was on a national speaking circuit addressing university and seminary faculty and students about these matters, I learned that many people in contemporary culture are hungry for this same integrated approach.

Over the coming months, we will be adding more ways of understanding horses to this website, and another blogger will join me in posting insights, questions, and thoughts.  For now, there’s this first post.  I hope you find what’s written here evocative and useful.  If nothing else, I hope it makes you go outside and look at your horse in a new way, maybe even one where you’ve got your head tipped to one side and a big grin spreading over your face.

Here’s to you and your horse!  Long may you run, together!