When watching a horse trotting up, I am often reminded of the saying "you cannot see the wood for the trees”. As a physio I have to look at both the wood AND the trees: I have to assess how your horse moves as a whole, as well as focus on the composite parts which facilitate this movement. I’m not just being cruel when I ask you to run up and down with your horse a few times!
The study of biomechanics within kinesiology allows for a more scientific approach to an area of common sense; for example we all know that longer strides make for better speed and a comfier seat, but they are also more gait efficient and less likely to cause undue stress and damage to the body in the long-term. Understanding what constitutes ‘ideal’ and ‘less-than-ideal’ conformation can help provide an insight into what a horse may predisposed to and help us create a plan for their training and care. Here, I have outlined a few examples where conformation can affect movement...
Head and Neck
Combined, the head and neck account for around 10% of the horse’s total bodyweight. They influence movement, posture, balance (acting as a pendulum to shift their centre of gravity) and distribution of weight. Neck muscles like the Brachiocephalicus and Cervical part of the Trapezius help to pull the forelimbs forwards, and the way in which the neck is set onto the thorax impacts on the shoulder. The image below shows a neck nicely set into the thorax, with a clear throatlatch behind the head.
A heavy, low-set neck can lead to horses being heavy on the forehand, making them more at risk of developing lameness. Horses with these types of necks also have a tendency to pull themselves along rather than push from behind, predisposing them to shoulder muscle problems and an underdeveloped, weak back end. They may also struggle to achieve good flexion. The aim with these types of horses is to get them off their forehand, carrying their head correctly and engaging their hind-end so that all of the weight (horse and rider) is distributed more evenly.
Back
This aspect of a horse’s conformation has an almost exponential level of influence on the way in which a horse moves and it will not be the last you hear about it from me! However, it is just as affected by other aspects of conformation. It constitutes the thoracic, lumbar and sacral vertebrae; superficial muscles including the Longissimus Dorsi and ligaments (suprasinous, longitudinal, etc) – all working with the thoracolumbar fascia. These are not simply important in their own right, but more so because they provide origin and insertion points for a lot of other muscles!
A back is considered to be proportionate when it measures roughly one third of a horse’s total length. A ‘long’ back lengthens the link between the front and rear of the horse, making it subsequently weaker – lacking balance and unable to carry weight efficiently. Longer backs are also prone to developing lateral swing when the horse moves, putting pressure on the spine, muscles and ligaments. Those with ‘short’ backs - though more desirable for their considered strength - are more likely to over-reach their hindlimbs, pulling off shoes and causing injuries to the forelimb tendons and ligaments. The picture below shows a short-backed horse as demonstrated by the stickers: the most posterior marks the site of the eighteenth thoracic vertebra; ideally, this should not be exceeded by a saddle.
Both cases require extra support from the abdominal muscles to stabilise the spine, ligaments and back musculature. Getting the horse to engage their core is key, and again it is a combined effort between riders, owners and therapists to achieve this.
Hooves
Hooves are the only part of a horse’s conformation which can change over time – constantly growing, in contact with whatever surface the horse is travelling on, and seriously affected by the horse’s movement. It is therefore vital that they are professionally attended to on a regular basis to ensure that they remain healthy and stable, affording the horse greater ease of motion. Hooves should ideally have an angle of 45º for the forefeet and 50º for the hinds – the angles should mirror the line from the coronary band to the toe. Hooves should be equally sized, level and have no flaring (although mild asymmetry is commonplace and therefore not necessarily associated with poor movement).
Flat and wide feet are generally weak and leave the sole more exposed to bruising; their poor efficacy of movement has repercussions on the rest of the limb, predominantly on the tendons and ligaments. Upright, narrow hooves reduce the surface of impact with the ground, resulting in more pressure being exerted on the limb and making the foot vulnerable to concussion.
Hooves which turn either inwards or outwards – be it unilateral or bilateral – can cause uneven wear, but more significantly can be a precursor to lameness as the horse moves in an irregular fashion to compensate; these repercussions will also have to be addressed, along with the original lameness. The image above clearly shows the horse's forefeet turned inwards, whilst the hindfeet turn outwards - both will put pressure on the structures above and I would not be surprised to find tight spots higher up!
Whilst conformational issues in the feet can lead to problems elsewhere in the horse by influencing locomotion, the distribution of wear on the hooves is indicative of how the horse moves. Uneven wear may therefore suggest an inefficacy of motion within the limbs. Again, I could happily go on for hours about hooves and their relationship with the rest of the horse, but I shall have to leave that for another time; so with that threat fresh in your mind...
...To sum up
The simple fact is that all aspects of a horse’s conformation from a symbiotic relationship, each influencing the other and all impacting on the overall way of going; the horse’s movement will in turn affect features of conformation. The study of biomechanics is essential to understanding how these aspects function and influence the rest of the body, how they can affect soundness and how they impact efficacy of movement. We can then work towards exercising the horse in a manner which may be more complementary to their conformation, and help them using remedial shoeing and physical therapies – the key point is that it’s a team effort! The more we understand about how our horses’ move, the more we gain to benefit them.
Modern study of biomechanics in kinesiology allows us to view the horse like never before - in individualised segments and as a whole, often in a simplified, schematic way, using techniques such as video analysis. For further information on this topic, I thoroughly recommend having a look at Centaur Biomechanics’ fantastic publications at www.centaurbiomechanics.co.uk.
Jess Eyres
J. Eyres Equine Physiotherapy, September 2020.
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