Another week, another muscle. Today’s spotlight is for the: Brachiocephalic The Brachiocephalic is a mainly superficial muscle located in underside of the horse’s neck. It is quite a long muscle that is actually incompletely divisible into two parts: the Cleidocephalicus and the Cleidobrachialis.
The Brachiocephalic has two main origins. The first origin attaches at the mastoid process and nuchal crest of the skull. The second origin attaches at the Omotransversarius, the wing of atlas and the transverse processes of C2-C4/C5. From there, the Brachiocephalic passes over the Biceps Brachii and Brachialis before inserting with the superficial pectoral onto the deltoid tuberosity and crest of the Humerus (shoulder joint).
The Brachiocephalic has multiple functions:
- It laterally inclines the head and neck to the same side of contraction
- It draws the front limb forward when the head and are fixed
- It extends the head and neck when the limb is fixed
As such, the Brachiocephalic is extremely import for proper shoulder and front limb action as well as lateral flexion. By doing so, the Brachiocephalic acts as an antagonist to the Trapezius Cervicus – see previous post. Furthermore, it also has an interesting relationship and action with the Cutaneous Coli – which adheres to the Brachiocephalic. Interestingly, the Cutaneous Coli seems to potentially acts as part of the thoracic sling upon landing. As such, horses that jump or often work downhill might show pain upon palpation where it adheres to the Brachiocephalic muscle.
In quite a bit of horse’s the Brachiocephalic appears to be under some strain. The muscle can feel hard and show up bulging. So what could cause this phenomom?
1. Poor Posture A horse with poor posture often uses its neck to balance. So horses that lack proprioception or generally struggle with self-carriage often develop the neck ‘upside-down’ – ewe necked - as they’re contracting the lower part of the neck muscles to balance. Especially self-carriage is a really important factor here. Poor posture can be derived from anatomical abnormalities, caused by improper training or the result of trauma and/or neurological deficits. I will elaborate on some of these causes in the next points. 2. Anatomical variations and abnormalities As mentioned in my earlier post, the Trapezius Cervicus acts as an antagonist to the Brachiocephalic. In some horses, the space between these muscles is narrowed (anatomical variation) and this limits the so-called ‘freedom of the shoulders’ and front limb mobility.
Abnormalities in the vertebral column also often cause strain and hypertrophy of the brachiocephalic. These range of these issue include C6-C7 malformation, arthritis, scoliosis, recessed ribcage / rib trauma, kissing spines, transitional vertebrae and inverted rotation. Finally, elbow instability (arthritis) and unbalanced feet – especially the front hooves
– can also play an important factor.
Please keep in mind that anatomical abnormalities – especially when they’re asymmetrical – will ALWAYS affect movement and posture as logic dictates that asymmetric form comes with asymmetric forces. As such, most of the times the question is now whether we can ‘fix’ these horses, but how we can manage them the best way to enhance their welfare. 3. Discipline use Since the Brachiocephalic acts as an anchor to extend the front limb, it becomes under quite some strain in most disciplines. Think jumping, dressage, western disciplines and harness horses. However, that being said, the way the horse is being trained in those disciplines - balanced and in SELF-CARRIAGE or not - makes ALL the difference. So while strain on the Brachiocephalic might lie in the nature of many disciplines as they require lots of lateral flexion and front limb movement, this is not by any means an excuse for poor training practices, which brings me to my next point. 4. Poor training practices Rider’s that lean on the reins or hold the horse back will compromise the horse’s freedom in and self-carriage in the front end. Same goes for side reins. The thoracic sling can’t engage properly, the front limbs can’t provide a vertical incline against gravity and as such the Brachiocephalic is under a lot of strain and the horse’s neck will develop ‘upside-down’. Since the horse’s neck is essential for proper neurology and balance control, you risk quite a lot of potential injuries by applying poor training principles. The key to any good training is balance and lightness … in SELF-CARRIAGE. A ‘handy’ rider can use some ‘tricks’ to keep the horse between the aids in a mechanical balance, but that doesn’t create self-carriage. To work on self-carriage, remember that you are basically working with the horse’s brain. So train intelligently. Train smarter, not harder.
Finally, the Brachiocephalic can become impaired because of a pull back on the halter – especially at the poll. Furthermore, kick and or bites could also result in quite nasty scars and tears in this muscle. Please do NOT underestimate scars. They can be very sensitive and painful.
Thanks for reading, I hope it provided some insight. Like these posts? Than like this page for more updates or check out my website for plenty of articles and an online program!