Monday, January 11, 2016

Muscles of Balance


The muscles of the balanced horse provide a well defined
shape from head to tail.
In the discussion of maintaining and developing ideal physical form in the horse I’ve decided to remove the dreaded “C” word that seems to set nerve endings jangling in equestrian circles.  I believe if we can agree to discuss the horse as a general athlete, able to correctly perform a number of athletic and advanced maneuvers as well as maintain sustainable form to function, we can maybe agree to use a more general term.  I would like to, therefore, discuss balance in the equine frame.



The horse evolved for one purpose on the plains of this earth.  He evolved to survive.  He became fleet of foot with a long neck that was able to get to the often sparse grasses on the plains.  The eyes were large and set wide apart to allow for greater vision while in the grazing position.  The skeletal frame was designed to effortlessly carry the horse across miles and miles of ground without tiring in the pursuit of food, water, shelter and safety.  To that end the basic equine frame is one in which the top line is level.  In grazing stance or periods of rest the center of gravity shifts forward and in movement in a level frame shifts more towards midline to even the distribution and concussion of the forelimbs.  Forelimb performance lameness as we know them in the domestic horse including, navicular, laminitis, pastern arthrosis (ringbone) and arthritis are largely unknown in the wild horse population despite the 15-20 miles the average wild horse travels in a day.

Now, we have to be careful in comparing our domestic horse to the wild horse in all but form to function because we are making demands on our horses that are completely unnatural.  Sure, a horse in the wild is capable of performing Levades, piaffe, canter pirouettes, sliding stops and lofty extended trots.  They do not however, perform them with a large weight in the middle of their spinal column, nor do they sustain those movements for long periods of time.  Most of us in decent physical health could perform a burpee.  How many of us could perform 10 of them in a row without extreme fatigue?  In my circle of friends probably only a handful.  Now do that with a young child riding on your back.  Yeah, not near so easy.  It takes conditioning and muscle strength and suppling in order to correctly perform athletic maneuvers without causing undue stress, strain and wear and tear on normal joints.

Think about what lies below your saddle as you ride
So, our goal as we ride and condition our horses in the hopes of developing a sound, athletic body is to create balance and suppleness through the entire frame.  Like any good athletic coach will tell you this starts with a good working knowledge of how the body is put together. 
Let’s begin our discussion by looking at the frame work.

The equine spinal column is composed of three arcs.  Unlike the human skeleton which is designed to carry weight in a mostly upright position on a bipedal frame, the equine skeleton obviously distributes the weight fairly evenly along the spinal column to distribute weight along all 4 feet.  As we have already discussed in a grazing position, that balance shifts to carrying the weight more on the front feet, but in times of athletic movement that weight shifts back to the business end of the horse allowing for rapid acceleration and quicker turns. 

The three arches in the equine skeleton are:
1:  The 7 cervical vertebrae running from the head to the chest.  
2. The 18 thoracic and 6 lumbar vertebrae running from the withers to the loin.
3. The 5 fused sacral and caudal vertebrae running from the loin to the tip of the tail. 

In an athletic stance we would like for all three of these arches to be evenly engaged, effectively rounding out the entire horse.  In neutral the arches form one long low arch.  It is interesting and instructive to note that the lateral mobility of the equine spine is largely limited to the first and last arch.  The lateral movement through the thoracic vertebrae is limited at best and the loin and fused sacral vertebrae allow for virtually no lateral movement at all.  The only direction the lumbar-sacral joint is able to make is vertically allowing for coiling of the pelvis and flexion of the hip.  Because the lumbosacral joint has dorsal/ventral flexion of only 6.5 degrees, the majority of the flexion in the back of the horse occurs with flexion of the hip.


Not only are we attempting to develop a frame on the horse capable of athletic movement, we also must build the muscles responsible for carrying our weight without causing injury or excessive wear and tear on the horse's frame as well.  When the horse is first mounted he will drop his back away from the weight of the saddle and the rider, as one could expect.  The horse does this by extending his spine, contracting the long muscle of topline called the longisimus dorsi.  This is also the longest muscle in the horse's body and runs from the transverse processes of the last 4 cervical vertebrae along the transverse processes of the thoracic vertebrae and inserts on the dorsal processes of the lumbar vertebrae.  This causes the reverse arch through the thoracic vertebrae under the saddle and generally flattening of the first and third arch as well.  Stiffening of this long muscle due to fatigue or pain impairs the ability of the horse to round underneath the saddle.  Obviously that’s not ideal and as riders it’s our job to help the horse learn to deal with the weight and build the muscles that will allow it to carry the weight in a balanced frame. 

There is only one way to do this correctly.  And if you examine the muscles off the horse’s body in relation to the design of the equine frame it becomes obvious how training methods can get in our way and build the wrong muscles in our horses that effectively impair balance and form to function in young horses that carries through their entire lives. 

The muscles that are responsible or initiating coiling of the loins and the beginnings of balance through the topline are the hip flexors.  They are the muscles responsible for the thrust that drives the equine body forward.  When these muscles contract the lower the croup and loin loading the hip for the thrusting phase of the movement.  This spring like action carries forward into the 2nd and 1st arch like loading a spring.   When the hindquarters are not brought into play first and you attempt to create arch through the horse’s body by compressing or flexing just the head and neck, this drives the neck down into the thorax, flattens the back and pushes the hindquarters out behind the horse.

There are several ways to help your horse begin to develop the muscles that flex the hips.  Hills, going both up and down work these muscles efficiently.  Backing your horse, as long as he is stepping correctly in a trot back also develop the muscles of the hip flexors.  Lateral movements such as shoulder in, haunches in and leg yield also cause the horse to work the muscles of the hip flexors.  Any movement that asks the horse to step deeper underneath himself while still maintaining propulsion will improve the strength and flexibility of these flexor muscles. 



The muscles that are responsible for flexing the hip and coiling the loin may not be the muscles you think of when you look at the back of your horse.  The western horse is prized for big beefy hip muscles that extend well beyond the point of the him creating that luscious J-Lo look.  Those are the semimembranosus and semitendinosus muscles and they are responsible for extension of the limb and help to propel the horse forward in the stride. These are the very muscles that helped give the American Quarter Horse his name as they are responsible for quick burst of speed that is generated by these powerful thrusting muscles.  
The muscles of flexion are deep and hard to see. 
They are not, however the muscles that coil and flex the hip.  The hip flexors live deeper and include the Psoas major and minor, tensor fascia latae, gluteus superficialis.  These muscles work in opposition to the large semi m and semi t muscles on the back of the leg.  In fact, suppleness through those muscles is as important as strength in the flexor muscles when allowing the horse to coil the loins.  Some even suggest that the long muscles of the hip are equivalent to a second top line that allows the horse to stretch forward and step underneath himself allowing the balance of the horse to shift further back towards the loin.
 
The second arch of the spine is the thoracic vertebrae and loin.  We wish to develop muscles that lie below the transverse processes of the vertebrae rather than above them.  So while we, as horse owners spend a lot of time talking about developing a horse’s top line, it is not building the muscles of the top line as much as making sure those muscles remain soft, supple and flexible.    While we need good muscle tone along the top of the back for strength when carrying weight, these are not the muscles that are most effective in creating arch and loading the spring of the spine.   If you have ever seen a sway backed horse that is also in good flesh you will note that the dorsal processes (bony projections at the top of the spine) are not very evident.  This is because a sway back is not due to lack of muscles along the top of the spine.  Contraction of muscles dorsal to the transverse processes causes the spine to hollow.  Horses that are worked in this hollowed frame (park horses, harness horses, and often gaited horses) will have well developed muscle tone along the upper spine and poor muscle tone below the spine.  In order to cause the spine to round up and load the arch we need to work the muscles that lie below the transverse processes.  These muscles are involved not only in elevation of the spine but in lateral movements as well.  This is why lateral movements through the rib cage help to build strength and suppling in the muscles responsible for rounding of the spine.   BEND is the key to lateral strengthening as well as balancing and rounding the mid-section of the horse through loading of the muscles below the spine.  We need all of the muscles working together to strengthen and balance the horse.

The muscle groups responsible for lifting and rounding the back are smaller than the muscle that extends the back.  Like in the 3rd arch it is important for the muscles of opposition to remain supple and loose in order for the smaller muscles flexing the spine to act.  These muscles include the rectus abdominus, iliospoas complex and longus coli scalenus.

Rectus abdominus is a large thin muscle that lies along the abdominal wall and slings the abdominal contents like a hammock.  It attaches originates at the 4th, 5th and 9th rib and inserts at the pubis by means of a large tendon.  This muscle acts to arch the back largely by flexion at the lumbosacral joint.  Therefore, when engaging the abdominal muscles, you aren’t lifting the back so much as flexing the loin that then acts on the vertebrae of the back to arch slightly. 

If you look at the horse's body as if it's a suspension bridge you can see how the 1st and 3rd arch in the spine will anchor the span of 2nd arch.  The muscles of the abdomen and back below the vertebrae help lift the back into the securing arches of the neck and loin.  If either the arch in the neck or the arch in the loin are lost, the roundness in the back will drop as well.  It takes each piece of the horse's body working together to maximize the potential in each body part.  The whole horse will be stronger if each of the body parts is doing it's job and working in harmony.  Think of the tail end of the horse as the end of the bridge that has all of the supplies for building the rest of the bridge.  First you start there, then you create a base on the other side and then you bring the two sides together.  

Now, I left the first arch in the horse’s body for last for two reasons.  First of all it’s the last part of the puzzle in creating balance.  The greatest part the head and neck play in the overall balance is in shifting the weight of the horse backwards, towards the second and third arch allowing for the center of gravity to shift more towards the hindquarters freeing the forequarters for lofty movement and lessening the concussion on the front feet and legs.  Too often people start to balance a horse by worrying about the “head set” before worrying about engaging the horse. 

Bulging at the 3rd vertebrae due to
enlarged rectus capitus muscle
In order for the horse to correctly soften and arch the neck from spine to head he must first lift the base of the neck where it meets the withers.  As these vertebrae lift you can see the engagement off the muscles just to the front of the withers and just in front of the saddle.  This sets the horse up for proper head and neck carriage.  If you attempt to create an arch through neck by only flexing the poll this compresses the vertebrae and causes bracing at the 3rd and 4th vertebrae.  


Again, the horse is bracing and breaking
at the 3rd vertebrae
A properly engaged head and neck should be larger in at the base of the neck than at the mid thoracic vertebrae.  It is easy to tell if you horse has been developing the wrong neck muscles because he will bulge behind the poll.  Think of the head and neck as lifting from the chest and extending upwards and downwards.  Some suggest it’s the action a horse makes when he is looking into a bucket.  The must first lift then stretch then give at the poll.  This makes giving at the poll the very last action in the engagement of the muscles of balance and softening of the horse from tail to head. 


So, what are the take home messages for the rider that has little interest in anatomy but lots of interest in riding her horse? Here they are.
IF your horse is using the right muscles you can see it in their entire body if you know where to look. 

Does your horse have a bulging hind end with hard muscles when viewed from behind? He may be spending a lot of time in extension or thrusting those hind legs forward from behind the stifle.  You want those muscles to remain soft and supple and LONG to encourage the horse to step underneath himself as much as his conformation will allow.



This horse's back is hollow due to over developement
 of the longisimuss dorsi
Does your horse have a taught ropey back? Again, this is another muscle that we want long and soft with even fill along the entire back.  If your horse spends a lot of time in the hollowed dropped back stance the longisimuss dorsi will pull the spine back away from the shoulders and create that deep pocket.  It’s worse in horses with long laid back shoulders that are built to carry themselves hollowed out (Morgans, arabs, Saddlebreds, etc.) When the horse learns to lift and round his back this muscle will soften and quit tensing.  You should be able to softly palpate the muscles of the back from the spine to the top of the ribs.
This horse shortens and drops his neck, causing a ewe
neck and over developement of the trapezius muscle



Does your horse have a dip right in front of the saddle? This is caused by collapsing of the cervical vertebrae and over development of the trapezius.  When the horse pulls the neck back towards the withers this muscle tightens and thickens.  A chronic head tosser will have a well developed shortened muscle here.  We want to see the horse’s neck lift up in front of the saddle when engaged not dip down.


What about the muscles at the base of the neck?  Those should also be loose and stretchy allowing for the telescoping of the neck.  Thickening or tightening of these muscles shortens the cervical spine and creates a ewe necked appearance.  The muscles at the top of the neck that are responsible for stretch and lateral flexion are the only muscles that should be enlarging in the properly worked and balanced horse.  Those muscles should be toned and even from the poll to the withers. 
If the poll is flexed or braced without proper engagement of the remainder of the neck you get thickening of the rectus capitus.  This becomes the widest part of the horse's neck, and is especially noticeable when viewed from the saddle.

The well developed and balanced horse will have even muscle development through his entire upper body with soft supple stretchy muscles along the topline.  Obviously not every horse needs to be an elite athlete, just like not every rider is an elite athlete, but knowing which muscles are the "wrong" muscles  and which are the "right" muscles for balance may help us spot trouble areas in our riding and keep our horses sound and healthy well into their later years!



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