By Gillian Tabor
Core stability is a current buzz term for specific methods of exercising horses to develop quality and control of movement as well as strength of their core muscles; there is also some good scientific evidence behind a lot of the concepts advocated. Core stability exercises can loosely be defined as therapeutic exercises to restore or enhance the ability of the muscles and their associated nerves, to control and protect the spine from injury or re-injury. Before these pilates-type exercises are implemented in all horses it would be useful to understand the reasons behind this positive shift in training and rehabilitation techniques, and why you should maybe consider adding these to your horse’s training regime.
Unfortunately, it is common that performance and non-competitive horses used mainly for leisure purposes have back pain. The modern advances in veterinary tools used to diagnose back pain, such as radiography (x-rays), scintigraphy (bone scanning), ultrasonography (ultrasound scanning) and diagnostic analgesia (nerve blocking) have meant we have a clearer idea of what is the likely cause of the problems. Causative factors such as conformation and breeding, training and tack fit as well as trauma have all been suggested as both primary diagnoses, which would be implicated as the main source of the problem or as a secondary issue, related to another clinical problem. For example, one common non-back issue that can create secondary back pain is lameness. As vets, therapists, owners, trainers and riders it is within our scope to reduce some of the risk factors that are associated with back pain. Whilst we cannot modify breeding or conformation, we can affect how the horses are trained, how they move and therefore how their posture influences their backs and how they function during exercise.
Anatomy of the horse’s spine
The horse’s neck is adapted for movement and can move through a large range of motion, which is primarily achieved through movement of the upper cervical regions and at the junction between the cervical and thoracic spine. In evolutionary terms this large range of flexion, extension along with lateral (side) bending and rotation had a useful purpose. Lowering the head (flexion) to reach the ground to graze and lifting the head (extension) to check the horizon for predators, are movements which needed to occur frequently. Modern day horses should be capable of the same movements although the frequency of exploring the full range of movement may be limited in the stabled horse, eating from mangers or haynets. Side to side movements are essential for checking out surroundings, interacting with herd mates and, in the mare, assisting foals with feeding and removing annoying biting insects for instance.
The main bridge of the back is composed of the thoracic and lumbar regions of the spine (figure 1). Whilst in training we seek to achieve a supple and swinging back, these sections of the spine are semi-rigid with a much lower range of motion than in the neck. The stiffness of the back is required to provide support for the large internal organs – the heart, lungs and intestines – and also functions to allow the energy (force) created by the large muscles of the hindquarters to come through the body to generate locomotion. There are varying amounts of flexion, extension, side flexion and lateral rotation at each of the joints between the vertebrae but the sum total of their range of movement is not large. However, this is a useful factor in the riding horse when we need this stiffness to allow the saddle and rider to be on their backs.
The largest amount of flexion and extension occurs at the junction between the end of the lumbar spine and the pelvis. This is to allow the hind limbs to reach under the body when increasing speed and length of stride. The pelvis itself is a rigid bony structure with only a few degrees of movement occurring at the sacro-iliac joints, between the sacrum and the ilial wing of the pelvis. Although, as with all the spinal joints, the actual range of movement achievable will depend on the ligaments and the bony anatomy of each side of the joint.
The vertebrae are supported in their positions by ligaments that are aligned to limit excessive motion in certain directions and allow movement in others. Very little influence on these structures is available to those looking to improve the horses back and reduce or prevent back pain.
Fortunately, there is scope to have an effect on the muscles that are also a key component of the spine and how it functions. The muscles that lie close to the vertebrae and those that travel from the hindquarter through the trunk supporting the spine are adaptable and, with knowledgeable training and rehabilitation, can be influenced.
Along the spine, lying above (epaxial) and below (hypaxial) the vertebral column, there are large muscles which span across multiple levels of the spine. The role of these muscles is either to create movement via contraction, with shortening of the muscle (concentric muscle action) and controlled lengthening of the muscle (eccentric muscle action), or to sustain contraction to stiffen the portion of the spine it crosses. When the main back muscle, longissimus dorsi, contracts the spine extends creating a hollowing movement or, if only one side is active, the spine is flexed to that side.
Incorrect or overuse of the muscles on the upper side of the back can have a behavioural effect, such as tenseness with increased alertness and anxiety, leading to resistance to commands and dis-obedience. It is also a common site to find injury and pain. The bridge section of the spine made up of the thoracolumbar regions, supported at either end by the forelimbs and the hind limbs, has a tendency to sag in the middle, pulled down by the weight of the abdomen. The additional weight of a rider causes the back to extend even more. The dorsal spinous processes, which project upwards from the vertebra, are then brought closer together which increases the risk of them impinging or touching as shown in figure 2.
To lift and flex the spine the muscles on the underside of the vertebrae need to be active. The balance between the upper and lower muscles is essential to support the vertebral column and to have a healthy back. Activating the abdominals can also be described as tightening the string, in the bow and string theory of spinal anatomy. The bow in this case is the bony spinal column (the vertebra that make up the back) that is then bent upwards or flexed, to draw the dorsal spinous processes apart, as the string, the horse’s abdominal muscles, are stretched. As shown in figure 3, lowering of the head has also been shown to increase the gap between these processes, which is a desired effect especially if there are concerns regarding kissing spines.
How this posture is achieved is very much dependent on the individual horse, its stage of training and its current status. For instance, has it been suffering from back pain, is exercise being re-introduced following surgery for kissing spine, or is it considered to be an essential part of routine training for a sports horse? Training aids can be used to influence posture but the choice of aid and whether it achieves the desired position, should be evaluated at each exercise session. The goal of training is to activate the core muscles, which are listed in Table 1. Commonly training aids are used when lunging the unridden horse and these include a pessoa, equi-ami, kavalkade rein, equiband system or traditional side reins with a bandage or elastic resistance band around the quarters. Research into the effect of the pessoa and equiband show they have a positive influence on the spine in horses without back pain, which is supportive for use in horses as part of their normal training. Understanding the actions of these aids can then be translated into use for horses suffering from back pain.
The deeper spinal muscles control the micro-motion between a few levels of vertebrae and these are called the stabilising or postural muscles. In humans, that suffer from back pain, these stability muscles have been measured with ultrasound scans and have often wasted away at the spinal levels in individuals suffering with back pain. In horses, a similar reduction in size and differences in symmetry between the left and right sides have been seen where there are degenerative changes to the level of the spine where these postural muscles are positioned. Using research from human physiotherapy practices, changes to the size of these muscles and, in particular one called multifidus, occur when baited / carrot stretches are regularly practiced for at least six weeks (Figure 4 &5). Increasing the size of a muscle is related to an increase in strength, suggesting that carrot stretches will develop the muscles that support and control movement deep in the spine. Whether these exercises affect back pain, either to prevent or reduce the clinical signs in horses is yet to be determined however this would seem a logical outcome, based on the function and anatomy of these muscles being similar to those within the human spine.
To enhance activity of the core muscles the use of trotting poles is also recommended.
As the horse has to flex each of the limb joints to clear either a pole on the ground, or even more so with a pole raised up, the leg muscles have to work harder. This increased effort will therefore require more activation of the core muscles to support the body and control the movement of the spine. The muscles of the limbs, quarters and the core also have to work more to push a horse if they are worked up a slope. Therefore, the inclusion of hills in a core programme should be considered.
As with all training programmes, a progressive approach to increasing the demand and challenge on the horse, both physically and mentally should be taken. Allowance for factors, such as timescales, to increase muscle strength and potential training induced muscle soreness must be made in the scheduling of exercise session frequency, length and intensity.
The risk of back pain in horses’ backs can be reduced, with correct training, to ensure a balance between the upper and lower muscles of the spine. Core stability exercises should be including in all training programmes for horses. Whilst there are no guarantees, as we cannot alter the underlying skeletal conformation, a strong muscular system including deep stabilising muscles, abdominal and muscles associated with the core, will serve to protect the spine.
Working with a knowledgeable therapist who can help you select the most appropriate exercises for each horse is advisable. Monitoring the progress and outcome of any training programme that has new and potentially challenging exercises is essential and this should be done with support of a therapist and vet.
Brown, S., Stubbs, N.C., Kaiser, L.J., Lavagnino, M. and Clayton, H.M., 2015. Swing phase kinematics of horses trotting over poles. Equine veterinary journal, 47(1), pp.107112.
Castejon-Riber, C., Riber, C., Rubio, M.D., Agüera, E. and Munoz, A., 2017. Objectives, Principles and Methods of Strength Training for Horses. Journal of Equine Veterinary Science.
Clayton, H.M., 2016. Core training and rehabilitation in horses. Veterinary Clinics of North America: Equine Practice, 32(1), pp.49-71.
Crook, T.C., Wilson, A. and HODSON‐TOLE, E., 2010. The effect of treadmill speed and gradient on equine hindlimb muscle activity. Equine Veterinary Journal, 42(s38), pp.412-416.
Stubbs, N.C. and Clayton, H.M., 2008. Activate Your Horse’s Core: Unmounted Exercises for Dynamic Mobility, Strength, & Balance. Sport Horse Publications.
Stubbs, N.C., Kaiser, L.J., Hauptman, J. and Clayton, H.M., 2011. Dynamic mobilisation exercises increase cross sectional area of musculus multifidus. Equine veterinary journal, 43(5), pp.522-529.
Tabor, G. and Williams, J., 2017. Equine rehabilitation: A review of trunk and hindlimb muscle activity and exercise selection. Journal of Equine Veterinary Science.
Gillian Tabor is a Chartered Physiotherapist who has been working as an ACPAT Veterinary Physiotherapist for over 15 years. In her own practice in Devon she specialises in physio for
horses and riders, with the focus on treatment and rehabilitation of competition horses. Gillian is the programme manager and lectures on the MSc Veterinary Physiotherapy course at University Centre, Hartpury and is undertaking research, both her own equine projects and supervising students. When not working she has two young Lusitanos to keep her busy and plans to progress up the dressage levels with them.