High-Speed Treadmill Testing – Under Threat | Trainer Magazine | European Trainer Article Index

Jan 20

Jan 20 High-Speed Treadmill Testing – Under Threat

Horses are introduced to a treadmill gradually and the time taken for a horse to become comfortable enough with the treadmill to exercise freely at high speeds varies between individuals. Testing is often carried out on the third day after the introduction of a horse to a treadmill for the first time. Perhaps one of the main advantages of high-speed treadmill exercise is that it provides a controlled and repeatable test. Veterinary surgeons are able to accurately measure how hard a particular horse is being pushed. The speed and incline of the treadmill is both recordable and repeatable and unlike turf or synthetic surfaces, the going on which the horse exercises does not vary at all either with the weather or different sections of the gallop. As horses are going ‘nowhere fast’ on the treadmill, it is possible to assemble a wide range of recording equipment close by and this produces the opportunity to record a variety of data simultaneously in order to achieve a comprehensive assessment of a horse’s athletic ability and identify any abnormalities. The control and repeatability of treadmill testing combined with the ease with which equipment can be gathered around a fastmoving horse has made it an excellent tool with which to conduct research. During the last two decades, research has been carried out on high-speed treadmills into several body systems of the horse. For example, Gleadhill et al. analysed kidney function during exercise back in 2000 and found that the thoroughbred is able to dramatically reduce its kidney function to allow itself to exercise to a high level. In 2001 Geor et al. used a treadmill to study the effects of Lasix® and nasal strips on bleeding and in 2002 Nyman et al. used a treadmill to study water intake and fluid shifts in horses at exercise. The equine gait has also been studied in detail on high-speed treadmills and work has been carried out into the effects of variables such as lameness and shoeing/trimming. Butcher et al. used a treadmill in 2007 to study digital flexor tendons in motion and they produced a theory as to why such injuries might occur – essentially that the deep digital flexor tendon becomes fatigued first leading to overloading of the superficial flexor tendon and the potential for injury. The controlled environment in which treadmill testing takes place has made them excellent for many ‘fair’ tests and one excellent example is ‘head-shaking’. This condition can be investigated whilst lunging or exercising outside, but several veterinary centres have used treadmills for the testing of ‘head-shakers’ to see what stimulates each individual. As the external environment remains completely consistent (the treadmill room remains the same), various stimuli, for example, light or noise, can be tested to see their effect on the individual horse. However, although the treadmill has been used as a tool for gathering information about several body systems of the equine athlete, by far the most common uses of the treadmill are for the investigation of a horse with either cardiovascular or respiratory disease leading to poor performance. It is a common scenario – a horse that gallops spectacularly well at home but in a race turns into the straight and stops like it has been shot. The jockey struggles to explain it; the trainer asks whether the horse made a noise to which the jockey replies “a little”. The racecourse veterinary surgeon is then sent to examine the animal but comes back some while later with no explanation because its heart, lungs and larynx all seem fine one hour after the race. If only we could know what is going on inside that horse during the last two furlongs of the race. This is exactly where high-speed treadmills revolutionised diagnostic veterinary medicine back in the early 1990s. The equine heart is capable of increasing its resting heart rate by as much as six to ten times when at peak exercise and hence it stands to reason that some cardiovascular abnormalities are not apparent until the horse is pushed hard. Perhaps the classic example of such a problem is atrial fibrillation. This is a rhythm disorder of the heart where it beats far too fast at a random and irregular rate. The result of this is that the chambers of the heart are emptied before they have filled completely, leading to poor blood flow and a lack of oxygen. Whilst some severely affected horses can be diagnosed by listening to their heart at rest, others only fibrillate when put under the pressure of a race. The diagnosis of such a condition became straightforward with the introduction of the equine treadmill. However, in the last five years the emergence of the digital ambulatory ECG recorder (portable ECG machine) has enabled the diagnosis of this condition with a horse exercising on its home track. In hindsight, this may have marked the beginning of the threat to the existence of the equine highspeed treadmill. Ever since its introduction, the number TRAINING 50 TRAINERMAGAZINE.com ISSUE 25 one use for high-speed treadmills has been in the dynamic diagnosis of equine wind problems. Since the 1970s, veterinary surgeons have been using flexible endoscopes to diagnose problems associated with the equine larynx. However, as it is not possible to scope a horse in the final two furlongs of a race, veterinary surgeons were using a combination of the findings of a resting endoscopic examination and trainer/rider reports to ‘guess’ at the most likely wind problem. The introduction of the equine high-speed treadmill revolutionised this as for the first time they allowed us to view the equine larynx whilst the horse was exercising at near-racing speed. As was so eloquently described by Franklin and Lane at the recent 2008 Cheltenham Thoroughbred Racing and Breeding Seminar, oxygen is the essential fuel for the muscular propulsion of the equine athlete. The horse has a massive, powerful cardio-respiratory system, but unfortunately air is inhaled and exhaled through a small unreliable larynx and a rather narrow complex nasal system, especially considering that the horse is an obligate nasal breather and thus does not receive any air through its mouth. It is for this reason that any abnormality in the upper respiratory tract of the horse causes a reduction in the amount of oxygen it receives. The result is that horses with wind problems tend to have reduced stamina through an inability to sustain oxygen-driven muscle function and the associated audible respiratory noises are caused by increased turbulence within the respiratory tract, usually originating in the throat area (pharynx and larynx). The volume of air that is moved in and out of the lungs every minute increases dramatically from a mere 80 litres in a resting horse to as much as 2,500 litres in a racehorse during fast exercise. Unsurprisingly, this puts huge pressure on the walls of the airway and they have to withstand large ‘collapsing forces’ especially when breathing in, not to mention the importance of maintaining an open airway when breathing out. The majority of the nasal passageways and the windpipe can withstand these pressures but certain sections of the respiratory tract such as the nostrils, pharynx and larynx only have soft muscular walls and as a result, are most vulnerable to dynamic collapse during exercise. Endoscopy performed during high-speed treadmill exercise has been the gold standard for the diagnosis of such problems for the last two decades. In 2006 Lane et al. reported on the findings of 600 thoroughbred racehorses that were scoped on a high-speed treadmill at Bristol University. Perhaps the single most important finding of their work was the conclusion that resting endoscopy is unreliable in the diagnosis of wind problems and should not be used in isolation in surgical decision-making or in the assessment of horses at the time of sale. Diagnosis of soft palate displacement from a resting scope was unsurprisingly poor but also notable was that nineteen percent of horses with a severe paralysis at rest were actually ‘normal’ at exercise and seven percent of horses with acceptable scopes at rest were obviously paralysed at exercise. It is findings like these that convinced veterinary surgeons around the globe that dynamic endoscopy was far more accurate than resting endoscopy; however, equine high-speed treadmills did not conquer the globe for a few reasons. EVERY specialist equine veterinary surgeon has a flexible endoscope yet there are only a few equine high-speed treadmills scattered around the world. It is possible to conclude from this that one of the main reasons why treadmill testing has not become more widespread is its lack of availability, but there are other reasons. The procedure is labour intensive, time-consuming and relatively expensive but the multi-million pound industry that is horseracing would have embraced treadmills nevertheless if the idea of a horse galloping and becoming exhausted whilst exercising on an artificial rotating mat had sat more easily with the horsemen. The basic fact is that horsemen have not been satisfied that exercising a thoroughbred on a treadmill until it is exhausted is either a comparable test to a race or a safe thing to do. The lack of a jockey, lack of other horses and difference in racing surface and environment means that treadmill endoscopy may not result in the same wind problems that would be seen whilst galloping at home or in a race. When horses gallop on the racecourse they are capable of reaching speeds in excess of 40mph. However, an equine treadmill cannot operate as fast (many struggle to exceed 30mph) so instead operators make horses fatigued by increasing the incline of the treadmill and simply exercising the horse until it is exhausted – some argue that this is a different type of fatigue to a race. Indeed, research into the comparison between exercising on a treadmill and ‘normal’ exercise has highlighted differences in heart rate, blood lactate and stride analysis and so it is not unreasonable to think that there may also be a difference in wind disorders. In addition, reports of horse and operator injury during treadmill testing have simply served to make owners and trainers more cautious to use them. The result of this is that veterinary surgeons have been searching for an alternative and they now appear to have found one – the over-ground endoscope. Over-ground endoscopy A prototype of the over-ground endoscope was fine-tuned using standardbreds in France in 2007 and the first equine overground scope was purchased jointly by the large flat trainer, Mark Johnston, and Glasgow University Veterinary School. The traditional flexible endoscope is made up of fibre-optics, which are essentially a system of multiple mirrors. However, the over-ground endoscope is actually a camera, which is inserted up the horse’s nostril and stabilised by attachments on the bridle. This, along with a pack on the rider’s back, transmits a signal to a monitor, which can be viewed as the horse does any work that the trainer wishes. Hence, it is possible to watch the horse working and visualise exactly what the larynx is doing when a horse is put under pressure and an abnormal noise is being made. Every small detail has been considered in its conception right down to automatic water flushes to clean the camera every few seconds with a further option to flush at the push of a button should the view be less than perfect for even a second. Just in case the findings are not straightforward, the video is also recorded and so can be analysed, assessed in great detail and sent to as many specialist wind surgeons for opinions as required. In addition, if the rider is equipped with a GPS wristwatch, the exact location and speed of the horse can be correlated to any endoscopic abnormality seen. THE initial impressions of this over-ground endoscope have been excellent and although the equipment is still evolving, a number of studies are underway to assess the value of this new test. At the time of writing, a scientific paper has been accepted for publication in the internationally recognised Equine Veterinary Journal outlining the findings of the dynamic scopes of the first 67 horses. Trainers all over the British Isles have been requesting that horses be analysed using the tool and an increasing number of veterinary centres are purchasing over-ground endoscopes. This equipment looks set to revolutionise the veterinary approach to equine wind problems, as for the first time, it is actually possible to visualise what is going on in a horse’s larynx whilst it is exercising on its home track. This may not only allow us to make completely accurate wind diagnoses for the first time, but just as exciting is the fact that it will also allow us to assess the effect of various interventions, for example, nosebands, bits, tongue-ties, the Cornell Collar and even wind surgery. Conclusion New technology such as the over-ground endoscope is incredibly exciting; however, the reader must remember that not every piece of new equipment stands the test of time and hence we should now consider the potential pitfalls of this tool. As horsemen seem to be fairly ‘happy’ with endoscopy in general, it seems that there is little doubt that more horses will be over-ground scoped in the next few years than would have been subjected to high-speed treadmill endoscopy. Whilst it is exciting that the wind operations which our horses receive are likely to be the right ones, it is possible that we may start to ‘over-diagnose’ problems and horses which are racing well but making audible respiratory noises may end up receiving wind surgery that could do more harm than good. In addition to this, although over-ground endoscopy will represent an equivalent test to a morning gallop, unless trainers are going to run ‘trial races’ especially for the diagnosis of a particular horse, then yet again it is not an equivalent test to a race. As a result, there are some who believe that in five years time over-ground endoscopy will be in use all over the world, but that high-speed treadmills will still be used for the cases which over-ground endoscopy cannot solve. When a horse is on a treadmill, the veterinary surgeon is able to watch both the horse and its larynx very closely and hence can keep the horse going for as long as necessary to obtain a diagnosis. However, when a horse is over-ground scoped, it is the rider that determines how hard the horse is pushed and the veterinary surgeon is powerless to influence the test. In summary, high-speed treadmills have revolutionised equine veterinary medicine over the past two decades. Research performed using them has been groundbreaking and diagnoses have been made, particularly with regard to cardiovascular and respiratory systems, that otherwise would not have been possible. However, technology waits for no man and the advent of the portable ECG machine and most recently the over-ground endoscope is now challenging the existence of treadmill testing. We are set for fascinating times ahead.

CLICK ON IMAGE TO READ ARTICLE (20 January 2009 - Issue 11)

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Nov 28 Adrian Maguire: the ‘hands-on’ horseman