The inspiration for providing information about equine motion muscles and comparative anatomy, comes from my students, colleagues, Reiki practice, clients, and of course, the horses – our greatest teachers.
For all equine sports and disciplines, motion is a crucial element. We make big demands on how horses move, where they move, and how fast they move. Understanding the ‘equine motion muscles’ is valuable information for any horse person.
It is also valuable to see how equine motion muscles correlate to the muscles and structures of the human body. With the acknowledgement that horses mirror us on various levels, making sure your ‘motion muscles’ are conveying exactly what you’d like them to, can profoundly impact your performance.
Psychological, emotional, spiritual and physical components are indelibly intertwined. Studying equine anatomy and its relationship to our own can yield extraordinary insights, and can help us understand ourselves and our horses better.
Comparative anatomy: horse and human
A fascinating example of how we affect the motion of horses, is through our body language; more specifically, our body’s language. There are anatomical correlations between horses and humans that resonate without our intervention. This is due to the compatibility of our operating systems as living beings on this planet. We are similar, right down to the cellular level. In addition to our mammalian physiology, we all have a tremendous capacity for various expressions of empathy, which is important to recognize.
In the illustration below, striking similarities between the human foot/lower leg and the equine hock/lower hind leg are observable.
Locate the calcaneus bone in the horse’s hock and in the human foot. Identify tarsal and metatarsal similarities. Imagine rotating the human foot so that the calcaneous is angled upward like it is in the horse’s hock. From there, it’s not too hard to imagine one longer metatarsal, and three phalanges extending from that metatarsal. Those three phalanges – the small bones of one toe – are analogous to the long pastern, short pastern, and coffin bone of the horse.
Note: Experiment and try to move like a horse. Bend from your hips so that your back is perpendicular to the ground (lean on something to support your ‘front end’), bend your knees, stand on your toes and try to trot in place. It’s not easy because we’re not meant to travel this way, but you may gain some empathy when you think of strapping something around your midsection and carrying weight on your back. You also may realize what an incredible spring and pushing mechanism the horse possesses…
The Achilles tendon in the horse and human, is also very similar. Locate it in the hock illustration to the right of the image. It has similar origin points (where muscles attach to an ‘anchor’, or a fixed place), and the same insertion points (attachment to bone that moves when muscle or muscles are contracted) as a human.
The Achilles tendon is also called the calcaneal tendon. The gastrocnemius and soleus muscles (calf muscles) unite into one band of tissue, which becomes the Achilles tendon at the low end of the calf. The Achilles tendon then inserts into the calcaneus.https://www.webmd.com/fitness-exercise/picture-of-the-achilles-tendon#1
The common calcaneal tendon is attached to the tuber calcanei [calcaneus]. In the horse it is composed of the following tendinous components: gastrocnemius, soleus, biceps femoris, semitendinosus and flexor digitorum superficialis muscles.http://www.ejpau.media.pl/volume14/issue4/art-04.html
Note: Another well known ligament, the plantar ligament, has similar anchoring places in both species. Injury or irritation to the plantar ligament in a horse is called a ‘curb’, and in the human, it is called plantar fasciitis.
The next time you work with a horse, note how relaxed your ankles and feet are, whether you are walking, running, or riding. You may even begin to perceive that one foot or leg is more tense than the other. You may notice other things as well.
If you have an injury, disease (i.e. arthritis) or tension in part of your body, it stands to reason that your pain – if it has produced a change or limitation in your range of motion and your flexibility – may convey itself to the horse.
The pain that manifests at specific locations within you, elicits your feelings about it; it draws your attention, and you focus on it. It usurps your energy system, like static running in the background. In other words, if you have mobility-flexibility problems – it may be unintentional but also possible – your horse will develop similar ones over time (but not for the same reasons).
This is a small example of what you can become aware of as you make deeper connections between your physical body, and the physical body of a horse.
Note: This includes your effectiveness from the ground; effective, purposeful and intentional communication, applying medications, training and exercising, in addition to your work under saddle.
On a more profound note: Because of these anatomical correlations, and the unavoidable, multi-level connections that are automatically formed between horses and humans – whether we’re aware of them or not – it is also likely, that if urgency, demands and expectations are part of your training regimen or approach [human imposed time restrictions are a different type of mobility-flexibility problem], that imbalance and injury will also occur in parts of the horse’s physique, psyche and energy system. If you are open enough and interested enough, it will teach you and others with absolute profundity.
Movement of a structured, almost immovable torso
Shown below, is a diagram of the horse. Included are muscles – mostly represented by lines, some with a transparent extension for simplicity – that are primarily involved with ‘initial’ motion.
Even though the flexor and extensor muscles of the forearm and gaskin areas contribute, they would not find their purpose in locomotion without the ability of the leg to swing forward and backward. It would be like standing still and lifting and lowering your foot without the notion of rotating your leg forward from the hip.
Once you’ve moved your leg forward, you’d have the opportunity to straighten your leg and reach forward with your foot. That’s why the swingers are illustrated here. Keep in mind; there are a lot more muscles in the horse that are designed to keep things ‘still’.
Many muscles around the torso for example, are designed for support and protection, not propulsion. Muscles of the spine are designed to prevent mobility for obvious reasons.
Note: There is no specificity in the horses anatomy for carrying weight. There aren’t an extra set of legs under the burden of a rider, nor are there slings carrying the torso from an imaginary point in the sky.
Over-extension and/or fatigue of these muscles increases the risk of serious injury, and under normal circumstances, all these muscles work in excellent harmony. Nature has provided the horse with a magnificent package…
Equine Motion Muscles
Here’s the basic rundown of the ‘equine motion muscles’ (and a couple of key ligaments), along with their names and basic functions:
1. Nuchal ligament: continuation of supraspinatus ligament. Attaches to rear of cranium or skull.
2. Cervical portion of Rhomboid muscle: scapular (scapula = shoulder blade) rotation, pulls head up when leg is fixed – pulls neck to one side
3. Trapezius: thoracic and cervical portions involved in scapular rotation
Ventral Serrate (#4 and #6): forms a sling, hanging the trunk from the scapula – raises thorax – unilaterally shifts weight to one side
4. Cervical ventral serrate: scapular rotation – pulls upper end of scapula cranially and ventrally, raises neck when leg is fixed, or pulls neck to one side
5. Thoracic portion of Rhomboid muscle: scapular rotation
6. Thoracic ventral serrate: scapular rotation, pulls upper end of scapula caudally and ventrally -possibility assist in breathing ‘in’
Note: The horse does not have collar bones, and therefore, the trunk is suspended in-between the shoulder blades by muscles. Any and all training and exercise methods that ignore the proper development of these muscles – especially under the weight of the rider, the equipment, and the restrictions caused by the handling of the reins – cause the entire spine and its neighboring apparatus to sink and become compressed. This limits the true, natural, innate, inborn motility and freedom of the horse. The horse’s body (and mind) is forced to compensate, which over time will reveal itself in mobility issues, lameness issues and other ‘idiopathic’ problems.
7. Latissimus dorsi: pulls leg back, moves trunk forward over advanced/fixed leg
8. Supraspinatus ligament: connected to all spinous processes of thoracic and lumbar vertebrae
9. PSOAS group
a. Psoas major: flexes hip, rotates thigh laterally – swinging stifle outward during motion
b. Psoas minor: flexes or fixes lumbar and lumbosacral joints; inclines pelvis laterally on loins
c. Ilio-psoas (pulls leg forward)
d. Iliacus component
10. Middle Gluteal: pulls leg back as in kicking – moves trunk forward over fixed leg in conjunction with latissimus dorsi; contributes to rearing and jumping
11. Deep Gluteal: pulls leg back and rotates stifle inward (rotate thigh medially)
All parts of the Biceps Femoris, Semitendinosus, and Semimenbranosis (#12, #13, #14) are collectively called the hamstring muscles. They extend the hip, stifles and hock in bringing the leg back during forward movement. They are also responsible for the action of rearing, kicking and jumping.
12. Semitendinosus: extend hip and hock, flex stifle and rotate thigh medially during backwards motion of the leg
13. Semimenbranosus: extends hip, adducts leg
14. Biceps Femoris: extends hip, stifle and hock in leg retraction and locomotion
a. Cranial (toward head) part of Biceps Femoris: exends hip and stifle
b. Middle part of Biceps Femoris: extends hip
c. Caudal (toward tail) part of Biceps Femoris: flexes stifle, extends hock
15. Accessary tarsal tendons: extend hock
16. Gracilis: adducts leg and extends stifle and hock
17. Adductor: adducts and retracts protracted limb
18. Sartorius: flexes hip, adducts leg
19. Tensor muscle of lateral femoral fascia: flexes hip, extends stifle, tightens femoral fascia
20. Ascending Pectoral: retracts leg from forward position, draws trunk forward over advanced leg
21. Subclavius (pre-scapular part of deep pectoral): similar to ascending pectoral, assists ventral serrate in suspending the trunk
22. Brachiocephalic: pulls leg forward, lowers head and extends neck when leg in fixed position. Can move neck to one side.
23. Sternohyoid: pulls tongue and larynx back and down in swallowing; fix hyoid when tongue muscles act
24. Omohyoid: pulls hyoid and root of tongue toward tail
25. Omotransverse: similar to Brachiocephalic
26. Sternomandibular: bilaterally pulls head and neck down; unilaterally flexes head and neck to the side
Here’s another example for the application of this information. During my time as a coach and instructor, this was invaluable…
Many riders, especially dressage riders, encounter the infamous ‘bulging shoulder’ at one time or another. You now have the knowledge and power to think about how you might use your own brachiocephalicus and thorax muscles to help make corrections. This includes your breath and breathing habits, which greatly affect your fluidity and performance, and therefore, affect your horse’s fluidity and performance…their capacity for mirroring every aspect of you, is awake, alive, humbling and astonishing…