If we look at the horse with a view to performance there are two distinct but interrelated structures; its skeleton or framework, and the musculature which moves that framework.
Framework
	The framework of the horse should be as near as possible to correct conformation for durability. Obviously perfection is hard to find but too many weaknesses must rule out a horse destined for top performance. At the end of the day muscle strength and power is only as good as the limbs it is working.
	The skeleton can be divided into the relatively rigid structure of the backbone and the moving parts, the limbs and head. Correct limb conformation is the subject of much discussion and investigation but the design and function of the backbone or spine is equally relevant. The horse's spine is relatively rigid - unlike the human spine the intervertebral discs are extremely thin; there are seven cervical vertebrae, eighteen thoracic which are associated with the ribs, and six lumbar. In most horses today the transverse processes between these are fused, five fused sacral vertebrae and eighteen to twenty two coccygeal making up the tail.
	The reason the vertebrae of the sacrum are fused relates to the horse's way of going. Essentially the horse is rear wheel drive - power created by the hind limbs is transmitted along the back, the weight being taken by the hindquarters thereby allowing the front end to lift off the ground and the forelimbs which are not attached to the backbone to reach forward and stride out. The musculature of the hind quarters is very powerful, thus the pelvis is large, box shaped and rigid to withstand the forces placed on it by the muscles attached to it and the momentum they create. The hind limbs attach to the backbone via the sacro-iliac joint, the junction between the ilium of the pelvis and the sacrum of the back. It is this joint which allows the hind quarters to swing underneath the horse or engage, so correct function is essential.
	The better the horse can engage the hind limbs, his forward momentum will be potentially greater provided the conformation of the front limbs permit good reach.
	Movement in the head and neck should not be overlooked - the skull is extremely heavy and the horse uses it very much as a counterbalance for the body, hence the necessity for freedom of movement over fences etc. Therefore the ability to use the head and neck correctly as a balancer is important.
Musculature
	The musculature of the horse is fairly complex and consists of two to three layers of deep and superficial muscle over much of the body particularly the moving parts. Muscle is a relatively easy structure to train but will only work correctly if the underlying framework it is attached to is correct. Any problem in the framework will inevitably result in incorrect muscle function and development. In addition the superficial muscles of movement interrelate.
	We effectively have a circle of muscles running from the poll along the back, over the quarters and down to the hocks. A problem with any of these muscles within this circle effectively breaks the circle and impaired function or action results.
	The trapezius muscle which forms part of the circle sits directly above the muscles of the shoulder - a problem in the trapezius thus eventually affects these muscles of movement, thereby visibly shortening the horse's stride.
	The longissimus dorsi is the connecting musculature between the powerful hind quarters and the horses front end. Soreness or restriction here will tend to make the horses back hollow and dramatically reduce the degree of engagement of the hind quarters.
Muscle Dysfunction
	In the early stages restriction of the musculature due to tension seldom results in full lameness, rather the horse develops an incorrect way of going, frequently only noticeable on a circle. The earlier the cause of the problem is identified and dealt with, the better. The longer the spasm is present more musculature will become involved causing a greater degree of compensation that the horse will make for this discomfort.
	An holistic approach is thus essential. Not just to identify the cause but also to assess what other changes might result so that the sport therapist is able to correct these as well. None of this is possible without full veterinary referral to eliminate any structural problems. Close communication with veterinarian, rider / owner and trainer all contribute to a fuller picture of the horse's weaknesses and therefore assist towards a positive outcome post treatment.