Structure, posture and movement and whole horse wellbeing

How are anatomy, conformation and posture linked? How do these affect movement? And how is this linked to mental and emotional wellbeing? What can posture and motion tell us about all-round wellbeing? Can we influence these with our management, training and riding and if so, how do we do so beneficially and avoid detrimental effects?

At my recent Zoom Q&A call I covered these and other questions submitted by attendees. I am a veterinary surgeon, and have a strong interest in classical dressage and ethical animal training, or perhaps a better term for it would be compassionate behaviour change (and not just on the part of the animal). On a deeper level, my interest lies in the mutually beneficial development of mind, body and spirit between animal and human for better wellbeing. I believe animals have much to teach us in this realm, not just that we need to improve them in some way. When we ride horses, I feel it behoves us to cultivate an understanding of how horses can arrange and move their bodies in healthy ways when carrying us, for the safety, comfort and enjoyment of both horse and rider.

During vet school at The Royal Veterinary College I took an intercalated degree (a degree done in one year sandwiched in between the second and third years of vet school) because I thought I might want to go into research eventually. My subjects for this degree were Comparative Animal Locomotion, Skeletal Pathology, and Wild Animal Biology. An eclectic mix that I actually managed to combine in my dissertation on comparing the long bone shapes of fifteen different semi-aquatic tetrapod species (four-legged vertebrates that can both swim and move on land) and linking bone shape to how they move. I also spent two summers doing research studentships, one in the Structure and Motion Laboratory on how the body adapts its movement to rough terrain. I loved learning about animal locomotion and it has stood me in good stead, but have found listening to the horse far more informative in how we actually make decisions with living, feeling animals.

I’ll start by addressing the questions I have posed in the first paragraph, defining some terms because I hope I can clarify a few things by doing so. I will then cover the questions submitted for the Q&A call.

Anatomy is the structure of the body, its component parts and how they are related together. With some quite rare exceptions, it is the same in every individual of the same species. But differences in relative size, shape, position and development of anatomical structures, alone or in relation to each other, can change conformation, which is effectively the horse’s shape and body proportions. Conformation is not necessarily fixed for life. Posture is the position in which the body is arranged and held in space, and the reasons for the way the body is positioned and different parts habitually arranged and moved can be physical, mental and emotional. Long term, postural patterns can lead to changes in the development of certain muscle groups, tightening or stretching of fascial connections, and even remodelling of the shape of bones, to ultimately affect conformation. Conformation can also affect posture. Sometimes untangling the interactions is challenging, usually a chicken and egg situation. 

The reason I chose the title “Structure, posture and movement and whole horse wellbeing” instead of something like “Equine anatomy and biomechanics” is because I wanted to talk about the living, feeling horse rather than anatomical connections and lever arms. The term “biomechanics” has become popular in the horse world, often used to mean something slightly different to its strict definition, which is the study of mechanics as applied to living organisms. When the term is used in the horse world it is often more functional anatomy, the study of how components of the body work together, that is actually being discussed, than the physics of force application and moment arms. A sound understanding of functional anatomy will certainly improve our training and riding. I’m not so convinced about needing any understanding of biomechanics, and although the field has given science many very useful insights into certain aspects of animal locomotion, it also has its limitations. Just how translatable biomechanics findings are to making decisions on how best to interact with the living, feeling animal is definitely debatable. 

Another concept in the structure and motion of living organisms is that of biotensegrity. This is tensegrity as applied to living organisms, and tensegrity is in effect a different way of understanding how three-dimensional structures interact within themselves as a system and with the environment. I feel this has far more to offer us in our pursuit for understanding healthy movement than biomechanics does, as the interconnectedness of the system as a whole is inherent within it.

Here is where the whole horse wellbeing part comes in. Mind, body and emotions all affect posture and movement, not just physics. Posture and movement are a product of, and therefore a reflection of, body structure, neurology, pathology, comfort or discomfort, emotional state and conscious and subconscious decisions. Reading posture and movement can give us information on these underlying aspects, and affecting posture and movement can change them, in both the short and long term.

Let’s look at two examples of body parts that came up in the Q&A call.

The first is the temporomandibular joint and how restriction of this affects movement. The temporomandibular joint is the connection of the mandible, or the lower jaw, to the rest of the skull. In horses it is moving all day because they chew (or should) for about 16 to 18 hours a day. It also has a major function in proprioception, which is the sense of knowing where body parts are in relation to each other and in space, which way up they are, and how much they are being stretched or compressed. Proprioception is therefore intimately connected with balance and with movement patterns. Structures close to or connected to the temporomandibular joint include various cranial nerves, the hyoid apparatus which is a collection of relatively spindly bones that suspend the tongue inside the skull and connects via muscles to the sternum and ultimately to the pelvis, and the atlanto-occipital joint, the articulation between the skull and first vertebra of the neck, indeed the first vertebra of the entire spinal column.

There was a study where 1000 horse head CT scans were examined and found that 40% of these showed changes in the temporomandibular joint that could be considered pathological, however nowhere near 40% of horses are attributed to showing signs of temporomandibular joint discomfort. Is this because they don’t have discomfort or because we don’t know they do? Many signs distant to the actual joint could be indicative of either a primary problem of the joint, or at least pathology or discomfort in the joint. The multitude of connections to the temporomandibular joint mean that restrictions, pain or asymmetry in the joint can affect the way the horse holds and moves the spine, rib cage, pelvis and tail, with knock-on effects then on any structure these are connected to, in other words, potentially the whole body.

I am always looking at not just the physical aspects, but also mental and emotional. Being out of balance in terms of posture and movement is almost always associated with unsteady emotional states. Therefore it is certainly conceivable that restrictions, discomfort or asymmetry of the temporomandibular joint, that have effects on proprioception and balance, both lead to and could arise from, emotional states such as fear and anxiety.

Lastly, it is not possible for a horse to use their body in a healthy way for carrying a rider without release of the temporomandibular joint. This is a concept they will likely have to learn, with us being sensitive of when it is appropriate to apply a cue for this and when it might not be, but certainly without us ever purposefully inducing any restriction in this vital joint, for example through the use of auxiliary reins.

The second area that came up in the call is the relationship between the stifles and posture and movement, covered in a couple of different submitted questions. The stifle joints are the big hindlimb joints located next to the flank folds, they are the second joints down in the hindlimb, the first being the hip joint that connects the hindlimb to the pelvis. I wanted to bring attention to the iliopsoas muscle group because it is so influential on whole horse posture, including the stifles, and is also a great example of how emotional state affects posture.

The iliopsoas muscle group consists of three muscles that work together, they lie underneath the lumbar spine or the lower back and connect from there to the pelvis and femur, or thigh bone. They also connect to the diaphragm. The iliopsoas is majorly affected by emotional state - fear, pain and panic all causing it to contract, and a feeling of safety allowing it to relax. The iliopsoas can affect posture by being perpetually too tight or too underdeveloped and loose, or by one side being more contracted than the other, causing left to right asymmetry. Contraction will tuck the pelvis and this affects the hip and muscle groups of the upper hindlimb, and therefore the stifles. There is also a connection to the shoulders and thoracic sling, which if locked up or weak, affects how the horse can turn and can put strain on the stifles. This is an excellent example of how a long term level of anxiety could very conceivably affect whole body posture and movement. 

There are many excellent resources for learning more about functional anatomy. I particularly recommend anything by Jillian Kreinbring. Gillian Higgins of Horses Inside Out has made equine functional anatomy clear and accessible to learn. The Equine Documentalist has many excellent resources on the interconnections between the foot and the rest of the body, as well as ethology and effects of domestication on the whole horse. It is a huge and complex subject and I don’t think we can ever really say for certain that we know exactly how certain states have arisen, but only remain curious and listen to the horse in working towards posture and movement that makes them feel safe and well in their bodies.