ALL MAMMALIAN MOVEMENT stems from the soft tissues acting upon the skeleton, changing joint angles and stabilising the animal. The more effective the soft tissue function, the better the athletic performance. As soft tissues work, they heat up, not only because of the increased blood supply to the tissues, but also some of the elastic energy stored in the tissues is released as heat. This is why we ‘warm-up’ slowly, to enable the soft tissues to function at their optimum with the least possible chance of injury; the harder the tissue works, the greater the heat that builds up in that tissue.
If tissue is injured, however, then this evokes the body’s inflammatory response, which is part of the complex biological response of vascular tissues to harmful stimuli, such as damaged cells, or irritants. The classic signs of acute inflammation are pain, heat, redness, swelling, and loss of function. Indeed, this is why the vet will look for heat in tissues when performing a lameness diagnosis, but in subtle injuries, heat produced by a minor inflammatory response may not be felt, or the structure that is damaged may be too deep to ascertain increases in temperature by palpation.
Visualisation of this process has recently become possible with the use of thermal imaging.
What is thermal imaging?
Thermal imaging can detect even subtle changes in heat in a tissue created by the inflammatory response. Thermal imaging is non-invasive, emits no radiation and can be repeated as frequently as required.
Figure 5.1 Subchondral bone cyst in the left pastern denoted by the white portion on the thermal image.
Thermal images are obtained by using a special camera that is effectively taking ‘heat maps’ rather than pictures. In Figure 5.1, which is a thermal image of both front pasterns and feet in a horse, obvious thermal differences are seen between the right and left distal limbs. Normally, thermal patterns will be symmetrical but clearly there is an inflammatory response in the left limb because of the redder patterns. Differences in heat can be measured from the scale on the right of the image. In this image the thermal image has picked up what turned out to be a subchondral bone cyst in the left pastern denoted by the red and white thermal pattern from increased heat produced by the body’s inflammatory response.
Thermal imaging cameras are very sensitive to changes in the muscular, vascular, skeletal and nervous systems, detecting temperature differences of less than 0.05 °C, which is 40 times more sensitive than the human hand and can therefore detect inflammation in tissues which would not be evident upon palpation. So not only can it be used to detect injury and recovery, it can also measure the heat build-up in tissues as a result of exercise. In this way we can determine which muscles are working the hardest.
Photo 5.2 Thermal images can be discussed with the owner at the time of imaging.
It can be very useful in pinpointing areas of interest for further investigation by the vet or physiotherapist and images are available immediately. Photo 5.2 shows Helen Morrell of Surrey Vet Physio discussing with the owner a thermal image she has just taken of the horse.
Photo 5.3 Thermal images uploaded onto computer for digital transmission to a vet or physiotherapist together with the thermographer’s interpretation of the images.
Photo 5.4 A physiotherapist can use thermal imaging as a basis for selecting the appropriate treatment modality.
These images can be uploaded onto a computer screen (Photo 5.3) with the thermographer’s interpretation which can be emailed to the vet or physiotherapist and can be used as a basis for further veterinary investigation or treatment choice, such as massage therapy (Photo 5.4).
Thermal imaging as an aid to correct training
The use of thermal imaging can assist in the understanding and application of correct training principles when conditioning or rehabilitating a horse. Horses ridden and schooled correctly build up muscle symmetrically and in balance, with no tension or spasm, but horses allowed to run onto the forehand, for example, overuse the muscles at the base of the neck and at the shoulder. So how does that type of incorrect schooling reflect in the muscle build-up of the horse?
Figure 5.5 Ineffective application of the rider’s aids, so the horse is running onto the forehand. Note the red colours in the shoulder and base of the neck indicating this this horse is running on the forehand.
Figure 5.5 is a thermal image of a young horse being ridden incorrectly with the rider simply acting as a ‘passenger’ and failing to support or influence the movement of the horse, in much the same way as a beginner learning to ride would do. Effectively the horse is running onto the forehand. This image was taken after riding in this manner for 15 minutes (a typical warming-up session).
Bearing in mind that the ‘engine’ of the horse is in the quarters, it should be the muscles in that area which are the warmest. But in fact you can see that the warmest muscles (denoted by the red colours) are in the shoulder and the base of the neck, as the horse pulls himself along on the forehand, rather than pushing from behind.
Figure 5.6 The same horse ridden correctly. Note how all the muscles in the dorsal and ventral chains are working, and particularly note the difference of the angle of the pelvis to the previous image, demonstrating the ‘bow and string’ theory.
After a suitable period of rest in which the muscles have been allowed to return to normal temperature, the same rider rides the horse for 15 minutes in a professional manner. In Figure 5.6 you see the startling difference in the way the horse’s muscles are working. In this image the dorsal and ventral chains are working in harmony. Note the change of the angle of the pelvis from Figure 5.5 to Figure 5.6. The rectus abdominus muscle has pulled the pelvis closer to the sternum, opening up the lumbosacral joint and allowing the horse to bring the hind limb further underneath himself, radically rebalancing the horse.
These thermal images give a graphic demonstration of the importance of correct schooling, and establishment of balanced dorsal and ventral chains. Only then can correct posture be achieved leading to increased athletic ability and minimum risk of injury.
Photo 5.7 This horse shows good muscle development, dynamic conformation and athletic movement. (Courtesy of Sam Pawley photography)
How do these completely different ways of schooling and working the horse reflect in the appearance of the horse? Photo 5.7 shows a horse that demonstrates good athletic conformation with a strong, well-muscled neck, back and quarters, and toned abdominal muscles, allowing the horse a generous action. The dorsal and ventral chains are working in complete harmony, with the topline long and supple whilst the underline is short and supporting the weight of the horse.
Photo 5.8 A horse that moves predominantly from the forehand, with muscles in the shoulder region and at the base of the neck overdeveloped and sore.
In Photo 5.8, however, you can see a horse at the other end of the spectrum; this animal has, for whatever reason, a complete breakdown of dorsal and ventral muscular chains and is moving only on the forehand. The almost complete lack of muscle on the back and through the quarters is in strong contradiction to the overdeveloped muscles around the shoulder, base of neck and pectoral area which is entirely indicative of a horse which is unable to utilise the bow and string. The tension in the muscles in the base of the neck in front of the scapula is a clear indication that this horse is in pain. This muscle imbalance is completely explained by the previous thermal images.
Photo 5.9 Impinging dorsal spinous processes, a condition known as ‘kissing spines’. The spinous processes have rubbed against each other causing new bone formation and degenerative disease. (Courtesy of Equine Articulated Skeletons Inc.)
In addition, notice the dip in front of the withers; this is the classic sign of a horse that is blocking through the shoulder. Effectively the shoulder does not move as it should do as explained in the previous chapter. It is locked in a forward position by the cervical portion of the trapezius muscle, which is why there is muscle spasm at the base of the neck. This occurs at the extreme end of muscular chain breakdown. It is also evident that the horse is developing a sway-backed appearance as the abdominals have lost tone and are no longer able to support the back or abdominal contents. This can predispose the horse to the condition known colloquially as ‘kissing spines’ when the dorsal spinous processes of the thoracic or lumbar vertebrae impinge upon each other (Photo 5.9). Whilst we now know that many horses may have this condition without showing any symptoms, it can cause quite considerable pain requiring surgery or euthanasia.
The horse in Photo 5.8 has, however, reached the bottom of a very long downward spiral, and it is necessary to be able to recognise a horse that is starting to go wrong, long before he gets to that place.
Photo 5.10 Horse showing poor muscle development and posture as a result of incorrect riding.
1 Weak, undermuscled neck, back and gluteal muscles.
2 Overdeveloped shoulder and base of neck muscles.
3 Long, sagging underline with no abdominal muscle tone.
4 Note how the front legs are camped under as this horse leans heavily on his forehand.
In Photo 5.10 you see a horse that is on his way down that long spiral. The long muscles along the dorsal line are beginning to waste and become tight, shortening the topline, whilst the ventral line starts to sag and become long. The shoulder and pectoral muscles (which support the forehand) are becoming overdeveloped and sore because the horse is throwing his weight forwards as the ‘bow and string’ begins to fail and he cannot work properly from behind. This is what we generally term as ‘engine at the wrong end’ because the horse’s poor posture and discomfort have caused him to drag himself along from the front, rather than driving forwards from behind.
Photo 5.11 The horse with back pain will often find something in the stable to sit on (in this case the hay net) to relieve the pain.
As the back becomes increasingly sore a horse seeks ways in which to relieve the pain. Photo 5.11 shows a fit event horse that has qualified for Badminton, but who has become lame because of back and neck pain. You can see that that despite performing at a high level, he shows all the same characteristics of the ‘engine at the wrong end’ syndrome. The shoulder muscles are overdeveloped and the dorsal line is weak.
However, this horse has found a way to help relieve the pain in his back by sitting on his hay net. Horses in this situation will find anything in the stable to sit on, some sit on the door, some on the manger or a window sill. Signs of this behaviour can usually be noticed in the stable as these horses very often do not move from their ‘seat’ to defecate, and signs of faeces can be seen on sills, mangers or stable walls. If the behaviour has been chronic (of long standing) then you can even see indentations in the semitendinosus muscles that coincide with the height of the sill or manger they are sitting on.
These horses will require veterinary investigation followed by a long course of physiotherapy and remedial schooling (see Chapter 8) to bring them back into correct posture and a pain-free, functioning state.
The causes that start the horse on this journey of muscular-chains breakdown are manifold. It can be an injury, a fall, being cast, poor conformation or poor riding; however, it is much better to be able to recognise the signs in the early stages and seek professional advice before the horse’s poor posture and development lead to pain and lameness.
Imaging and treatment of problems
We can see the effects of tight, sore muscles in the back of a horse using thermal imaging.
Figure 5.12 Normal thermal image of a horse’s back (looking from behind the horse). Note that there is a line of red heat signature (indicative of an inflammatory process) down the vertebral column but the muscles on either side show no signs of abnormal heat and are symmetrical in thermal signature.
Fig. 5.13 A thermal image of a horse displaying pain on being ridden. Note the bright red colours indicative of heat and pain along the back. The diagnosis was one of multifidus muscle pain.
The thermal image in Figure 5.12 shows a normal horse’s back with the dorsal and ventral muscular chains functioning correctly. A symmetry of muscle thermal patterns either side of the vertebral column can be distinguished with no areas of abnormal heat patterns (which would show in bright red) indicative of spasm and pain. Compare this image to Figure 5.13, which is of a horse that demonstrates back pain. Note the bright red colours along the spine under the saddle area.
This horse was diagnosed with pain in the multifidus muscle manifesting when ridden, which was subsequently resolved by a course of physiotherapy and remedial schooling. This was a chronic condition which also included breakdown of dorsal and ventral muscular chains. Accordingly we can understand how the horse develops pain and tightening of the back in these circumstances.
At this stage it is appropriate to demonstrate how, if an injury is addressed immediately, it can be dealt with and treated very successfully, thus preventing the long downward spiral of posture compensation and muscular chain inhibition, leading to a chronic condition that will cause suffering for the horse plus the financial and emotional costs for the owner of veterinary/physiotherapy treatment.
Figure 5.14 Thermal image of a horse that has sustained a fall whilst competing.
In Figure 5.14 is a thermal image (from behind) of a horse whose left hind limb had slipped underneath him whilst competing two days previously and sustained a rotational fall. Although the horse was not lame, and the vet had ruled out major injury, the next day the horse presented with the inability to maintain right-lead canter and was becoming disunited behind. The owner was advised by her own vet that the horse had some acute muscle soreness through the back and left gluteal, and should be checked over by a physiotherapist as soon as possible.
On examination by the physiotherapist the next day (less than 48 hours post-injury), the horse was found to have mild soreness through the back but moderate spasm and pain in the left middle gluteal muscle, which was creating a pelvic rotation.
Figure 5.15 Thirty minutes posttreatment the muscles are relaxing and rehydrating.
Figure 5.16 Seventy-five minutes post-treatment the muscles continue to relax and rehydrate.
Fig. 5.17 Now, 120 minutes post-treatment, the muscles are almost fully recovered.
Soft tissue manipulation and mobilisation was applied by the veterinary physiotherapist, and imaging repeated after 30 minutes, 75 minutes and 120 minutes post-treatment. Within 30 minutes post-treatment we can see that the muscles are beginning to relax and rehydrate, thus becoming cooler as the inflammatory mediators are reduced (Figure 5.15). At 75 minutes post-treatment the muscles have continued to release and rehydrate and the thermal patterns on the left and right are nearly symmetrical (Figure 5.16). At 120 minutes post-treatment the horse’s muscles are now almost fully recovered (Figure 5.17). All these images were confirmed by palpation of the muscles by the treating physiotherapist.
The reason why this slow release takes place is because the muscles and the fasciae need to rehydrate and the inflammatory mediators need to be removed from the fibres. It is notable that after this type of treatment, the horse needs to rest and drink large amounts of water to enable complete resolution of the muscle spasm and rehydration. When a muscle is in spasm, not only do the fibres shorten, but the fascia contracts and the intercellular fluid is squeezed out. Therefore the fluid needs to be replaced to fully allow the fibres to lengthen and the fascia to expand to allow the rehydration process. It has been demonstrated that it can take up to four hours post-muscle release for the fascia to fully rehydrate, and the muscle to begin to return to full athletic function.1
Your physiotherapist will normally recommend 24 hours of rest and turnout before returning to ridden work to allow the body to flush the inflammatory mediators from the muscle into the lymphatic system.
Therefore the take-home message from this is that if you address muscle injury as soon as possible post-trauma, then it can be resolved and prevented from becoming a chronic condition leading to dysfunction of muscular chains and poor posture resulting in pain and loss of athletic function. Indeed at a subsequent physiotherapy assessment the horse in Figure 5.14 had fully recovered and was back to pre-injury performance levels.
Figure 5.18 Thermal image of a horse jumping. Note the warm thermal patterns over the shoulders and the middle gluteal.
As previously discussed, horses have an extraordinary ability to disguise injury by using compensatory gait patterns until such time as they cannot compensate any longer and their athletic performance deteriorates or they become lame. Figure 5.18 is an image of a young warmblood horse that is being trained for eventing and this thermal image was taken whilst the horse was jumping a fence at home. The owner had noticed that the horse worked considerably better on the flat on the left rein (with an inability to sustain right-lead canter) but jumped considerably better off the right rein. The horse is not clinically lame and the vet had referred the horse for physiotherapy.
In the thermal image you can see that the muscles of the shoulder are working particularly hard, as is the middle gluteal in the hindquarters.
Photo 5.19 Photograph of the warmblood in the previous figure; this photo was taken at the same time as the thermal image. Note the asymmetrical placement of the hind feet.
Photo 5.20 An elite jumping horse with good athletic posture uses both hind limbs equally in the take-off phase. (Courtesy of Nico Morgan)
Photo 5.19 is a photograph of the horse in Figure 5.18, jumping the same fence at the same time as the thermal image was taken. In fact, you can see the thermographer, Helen Morrell of Surrey Vet Physio, taking the thermal image on the right of the picture. However, of note in the photograph is the placement of the hind feet. It can be seen that the horse is greatly favouring the right hind limb to jump off. Compare this hind limb posture to that seen in an elite jumping horse in Photo 5.20 where take-off has utilised both hind limbs symmetrically and the hind feet are still together in flight.
In jumping disciplines, synchrony of the hind limbs at the take-off phase is vital. We discussed in Chapter 4 how the forces of the hind limb act against the rigid strut of the lumbar vertebrae to propel the horse forwards and upwards. If one hind limb is weaker than the other, or they are not used synchronously, the athletic jumping ability is seriously impaired. In fact, if you review the illustration of the ‘jumping skeleton’ in Chapter 4, it can be seen how important hind limb synchrony in take-off is.
Figure 5.21 Note the asymmetrical thermal patterns with the righthind locomotor muscles having a much warmer signature than the left.
When a thermal image is taken of the young horse in Figure 5.18 and Photo 5.19 post-jumping exercise, the results of this compensatory gait pattern are clear to see (Figure 5.21). The large locomotor muscles in the right hind are considerably warmer than those in the left, which barely show any response to exercise at all. Therefore the horse has been protecting the left hind, resulting in the ridden differences reported by the rider. As there was no presenting injury or lameness this gait pattern has arisen as a result of chronic locomotor compensation which may have originally been caused by injury which was not fully addressed at the time.
This completely explains the problems that the horse was displaying in that the right-rein canter could not be sustained because of the weak left hind, but he could jump off the right hind.
The ability of the owner of this horse to pick up on small issues arising during the course of normal training such as the horse showing different capabilities on different reins is, therefore, very important. There is no doubt that the postural compensations being displayed by the horse, whilst not yet causing lameness, would in all probability in a short period of time have gone on to have so overloaded that right hind limb that lameness was bound to occur.
Figure 5.22 An elite jumping pony jumping the same fence as the horse in Figure 5.18. This pony makes far more use of the hindquarters and less use of his shoulder (as should be the case).
Indeed if we consider the thermal image of an elite jumping pony (Figure 5.22) being ridden by the same rider, over the same fence and on the same day as the horse in Figure 5.18, there are many differences in the thermal patterns displayed by both animals.
The pony uses the hindquarters considerably more, and the shoulder considerably less, than the young horse with the postural problems. Because the young horse cannot use the hindquarters effectively, he places a heavy reliance on the forehand.
Photo 5.23 The young horse now jumps using both hind limbs after physiotherapy treatment.
But all is not lost for the young horse. After treatment by Gail we can see him in Photo 5.23 jumping cross-country using both hind limbs equally, and starting to win competitions. Because his posture has been corrected, he can become the sport horse that his owner deserves, and is not started on the downward spiral of postural compensations that would lead inevitably to injury.
So now we begin to get an appreciation of the importance of posture in the horse whatever function we put him to. Well-developed posture leads to strong dorsal and ventral muscular chains, effective bow and string function, maximum lumbosacral-joint movement, balance, athletic prowess and minimum risk of injury.
Right at the beginning of this book we emphasised that posture is the key to having the horse of your dreams, whether you want a happy hacker/trail horse or the elite athlete. In this chapter we have demonstrated this using thermal imaging. In the next chapters we will look at many of the problems you will encounter on your way to this goal, and how you can overcome them.
1 Schleip et al 2012, Journal of Bodywork and Movement Therapies, 16 94–100