Exercise Testing in Equine Athletes

By Celine Abela, Werner Bouwer, Jodine Koen.

Introduction

Treadmill testing

Field testing

Parameters tested

Conclusion

References

Introduction

Nowadays athletic horses compete in worldwide competitions for various kinds of sport, each with its risks. Therefore, these horses need to be maintained in their best shape physically. That is why multiple tests have been developed throughout the years to identify physiological, pathological, and physical problems. Exercise testing is used to evaluate the horse’s health.

There are two main kinds of exercise testing, both with their advantages and disadvantages. These are the treadmill laboratory tests and field testing. The clinic laboratory tests are usually favoured by veterinarians due to standardisation, but it has some downfalls compared to field tests, as field tests mirror the natural work environment of the horse better. Also, multiple parameters can be tested with these exercise tests.

Treadmill testing

“The main challenges in performing field tests lie in the ability to truly standardise them” – (Allen et al, 2016). That is where Treadmill testing comes in as it is a controlled way of testing for parameters in horses. Having the environment standardised will eliminate external or confounding, and so will not be able to influence the test. These exercise testing are carried out on more advanced equipment; this allows for finer readings and a vast area of data, that can be collected. There can be multiple speeds or inclinations used on the treadmill to better suit the test required. Moreover, in this situation, the horse is immediately, and more easily accessible, so that if any samples are needed right after the exercise test, such as blood drawing, they can be done.

Treadmill exercise testing has many disadvantages in many areas. “Treadmill exercise testing can be difficult to integrate into the management of an athletic horse”- (Couroucé-Malblanc and Erck-Westergren, 2016). It does not reflect the natural environment of the horse and where it works or competes. Apart from the obvious terrain difference, there are also more stressors in the field which are not accounted for in the laboratory. Also, the stride and gait of the horse differ between field and treadmill, as even if the speed of gallop used on the treadmill is the same as the race track the frequency of the stride does not match. Many studies comparing the results of heart rate and plasma lactate show significant differences between tests in the laboratory environment and the field. Therefore, even though the tests are repeatable they do not reflect reality in most cases. Another factor to take into consideration is the budget and willingness of the owner. These laboratory tests used expensive machinery and equipment, which makes the cost of the test on the whole very high. Moreover, treadmill exercise testing requires a lot of time. This is because the horse needs to be acclimated to the machinery and environment, and also trained to use the treadmill. Proper conditioning to the equipment can lead to the most serious disadvantage of the treadmill, as this can cause injury to the horse.

Yet the necessity of the horse to be acclimatised has been debated multiple times according to Couroucé-Malblanc and Erck-Westergren, (2016), as some performance testing laboratories do this and others don’t.

Field testing

The Field test is an exercise method that is used in the evaluation of various horses. Field tests are necessary to recreate the exertion that occurs during training and competition. Understanding the physiological effects of the effort that the horse experiences in each discipline, allows for improvement in the training and conditioning processes. “Biological characterization is key in determining the performance indices used to identify physical status” - (Allen, Van & Franklin 2016). Horses used in field riding are exposed to various conditions (weather, topography, etc). Therefore, it is very important to test the physiological change in the horses caused by the field training as shown by Ok-Deuk Kang & Yong-Soo Park, (2017).

The Major advantage of field testing is that the test can be conducted in an environment that is similar to the actual situation. Present studies also show that field tests could provide useful physiological parameters, such as VLA4 (the velocity at which blood lactate reaches 4mmol/L), V200 (the velocity at which heart rate reaches 200 beats per minute), and even V160 (The velocity at which the heart rate reaches 160 beats per minute). The surfaces, gaits, and speeds in a field test are more accurate, and more closely aligned to what the demands are, that the horse faces during exercise in genuine conditions. Field tests also account for the effect of the rider and may be performed without the need for sophisticated equipment.

The field test can be incorporated into the daily routine as a normal gallop session. The field test does not only give the researcher’s information, but it also gives the rider the ability to assess the horse’s fitness status, such as VLA4, V160, and V200, and it can discriminate horses of different races and fitness levels. In addition, this test can be completed regularly alongside a follow up medical examination to detect early physiological abnormalities. During treadmill testing, the horse needs to be acclimatised before to the treadmill before the actual test can be completed. With field testing, no prior acclimatisation is needed to perform the test as told by Audrey Fraipont et al, (2012).

Parameters tested

Heart Rate

Heart rate (HR), or the frequency of beats per minute, is an important parameter that is tested in equine athletes using exercise testing. This is used to determine the progression of training and also the condition of the horse's heart. HR response to exercise is measured by using electrodes placed in a thoracic girth strap placed under the saddle (Couroucé-Malblanc and Erck-Westergren, 2016). These electrodes are connected to a transmitter which sends the information wirelessly to the receiver somewhere on the horse, either the saddle or the rider. This can be done on a treadmill or the field, but on the treadmill, it might not be as accurate.

The HR is usually paired with some other factors, such as speed. The test will consist of multiple steps, where the horse needs to run at different speeds at equal intervals, with a small pause or walk in between. This allows us to make a graph of the heart rate against speed and from this graph, the V200 can be calculated. The HR response to exercise is linear between 120 and 210 bpm (Couroucé-Malblanc and Erck-Westergren, 2016).

Maximal oxygen consumption (VO2max) is another parameter that can be measured with exercise testing. This factor has no correlation with maximum heart rate (HRmax), but there is one between the percentage of maximal heart rate and percentage VO2max, even VHRmax has a relation with VO2max (Evans and Rose, 1987). This is significant as when VO2 cannot be measured directly it can be calculated from these other readings.

The HR can be affected by multiple factors; these include age and breed of the horse, the state of the horse, training type (competition type), and the track or terrain the test is done on. For the terrain, there is a difference in HR readings when taken on grass, sand, wood, or other track types, with sand having the lowest HR value. Yet interestingly enough the V200 was not significantly different in horses being ridden by lightweight riders and heavier riders (Couroucé-Malblanc and Erck-Westergren, 2016). Stress and excitement can also influence results as HR will be falsely higher in these states. This means for more accurate results the horse needs to be in a calm state.

Electrocardiography (ECG)

The ECG is commonly performed along with HR testing during exercise testing. This is used to examine the electrical activity of the heart, to diagnose arrhythmias that happen after or during physical activity. One study has shown an association between cardiac arrhythmias and peak HR during exercise in racehorses (Ryan et al., 2005). This is why it is important to surpass the usual exercise intensity of the horse suspected with the condition. Disruption of cardiac rhythm which manifests during exercise can result in poor performance of the horse.

Blood Lactate

Lactate is a metabolic product found in the blood; it comes from anaerobic metabolism in the muscles. Its values can give information about the horse’s aerobic and anaerobic capacity. “At rest, blood lactate levels are 0.5–1 mmol/l. During exercise, a bilinear relationship occurs between blood lactate concentration and velocity”- (Allen et al.,2016). Yet, it is mostly shown as an exponential curve. The blood sample is taken from the jugular vein and put into tubes containing fluoride-oxalate or lithium heparin as anticoagulants. It can be either kept as a whole without centrifugation or test carried after centrifugation with the plasma. The whole blood is preferred over the plasma as the lactate in the red blood cells is also measured this way, but the test needs to be done within 4 hours of sample collection. Plasma can last longer. “The aerobic-anaerobic transition or onset of blood lactate accumulation (OBLA) has been defined empirically as 4 mmol/l blood lactate concentration” - (Couroucé-Malblanc and Erck-Westergren, 2016).

Red blood cell volume and haematocrit

“Total red cell volume (RCV) is a major determinant of oxygen-carrying capacity.” - (Couroucé-Malblanc and Erck-Westergren, 2016). the haematocrit can be measured after maximal exercise and the total RCV to bodyweight was found to have a relation to maximum trotting speed in Swedish trotters, according to Couroucé-Malblanc and Erck-Westergren, (2016). The procedure used to measure RCV is not simple and cannot be done immediately. Yet it is still a useful factor to determine performance quality. However, in some breeds, this measurement is not a reliable test of quality performance, such as in thoroughbreds.

=== Aerobic capacity === “Exercise testing is used to measure the aerobic capacity of the horse. Aerobic capacity is best assessed by calculation of maximal oxygen consumption (VO2max)” - (K.J Allen et al 2016). One of the most frequently used tests is that of determining the VO2max. Especially when assessing the performance of the human athlete. Because” the competitive distance increases “(K.J Allen et al 2016). In the performance sector, VO2Max turns into a more important element of prediction. But other elements are also important to consider. “Particularly running economy, which influences the percentage of VO2Max that can be sustained during prolonged exercise”.(K.J Allen et al 2016).

In superior standardbred racing horses, a higher VO2max has been recorded compared to slower performing horses. An incremental exercise test is used to do the calculations for maximal oxygen consumption.” Oxygen consumption increases linearly with speed up until VO2Max. Which is defined as the point where no further increase of VO2Max is elicited despite further speed increases”- (K.J Allen 2016). The measurement of oxygen can be measured on a treadmill with an open or biased flow system. Or a breath-by-breath system-(K. J Allen 2016). Ventilatory data can be obtained by using the breath-by-breath system in combination with expired air alternatively open or biased systems can be used in a laboratory setting-(S.H Franklin et al (2010) Exercise testing can be an important tool to accurately determine the oxygen consumption of the working horse and can help to predetermine upper respiratory tract problems in horses-(J. G Lane 2006).

physical

The increasing professionalism of equine sports disciplines is putting an increased load of training on sport horses. The different disciplines of the equine sport require a different effort of energy from the horse in each discipline-(L. de Mare et al 2017). Professional equine trainers use GPS heart rate monitors on the horse that constantly monitors the heart rate of the horse, and the newest technology can even determine the inclination gradient of the surface that the horse is training on. “At a given point a standardised exercise test can be used, however, an important issue is which type of SET applies best for which type of sports discipline. A standardbred used for trotting requires another type of performance capacity than a showjumper” -(L. de Mare et al 2017).

“There are important differences in the exercise capacity between horse breeds” -(L.de Mare 2017). It is important to take into account that each discipline needs a specific set of abilities and its stamina level.

Thoroughbred horses

The performance of Racing horses depends on their aerobic as well as their anaerobic capabilities. Thoroughbred horses have been shown to reach a higher V200 value than other breeds that have been compared to it – (L.de Mare et al 2017).” Incremental standard exercise tests are less suitable for thoroughbred horses because of the difficulty to make them run at constant speeds and to control track conditions “(L. Plancke et al 2017). Therefore, a single-bout test is better fitted to assess the performance capabilities in Thoroughbred’s.

Eventing horses

During eventing, horses can run up to 6270m at an average speed of 34 km/h and up to 40 obstacles. During cross country, the heart rate of horses are found to be 170-210 bpm and they have maximal blood lactate concentration. The most common horse breed used for eventing is thoroughbreds or thoroughbred- crossbreeds. And most commonly a 3-4 incremental exercise test method is used. – (L. Plancke et al2017).

Dressage/Riding horses

Dressage has a minimum requirement of 4-8 minutes of demanding exercises. The heart rates rarely exceed 150bpm Which suggests that the used energy supply is partly aerobic during submaximal exercises – (L. Plancke et al 2017). Individual muscle groups also contract intensively during a selected dressage movement; therefore, the horses need strength as well as stamina. There are no specific tests yet to analyse the fitness levels of dressage horses- (L.de Mare et al 2017). “Submaximal exercise tests at low canter speed are recommended”- (L. Plancke et al 2017). These can range from incremental exercise tests on track they also include indoor riding tests as well as lounging tests. The Lounging test doesn’t need a galloping arena and does not need an experienced rider. It can be incorporated into the daily routine of the horse’s exercise schedule. - (C. de Meeus et al 2017).

Conclusion

Finally, we can see that within the two different testing methods used (field testing and treadmill testing) that there are different benefits in using each test depending on the parameters and sports disciplines that are tested. There is still a lot to be learned and developed regarding the testing methods, yet there has been great progress in the field throughout the years. In conclusion, the Equine athlete needs specific exercise testing in different areas to fully be able to get the specified results that are needed.

References

Allen KJ, Erck-Westergren EV, Franklin SH (2016): Exercise Testing in the Equine Athlete. Equine Veterinary Education 28: (2) 89-98.

Couroucé-Malblanc A, Erck-Westergren EV (2016): Exercise testing in the field. Veterian key. https://veteriankey.com/exercise-testing-in-the-field/#bib3 13/03/2022.

Aranzales JRM, Cabrera AMZ, Gutiérrez MPA, Soto MJC, Valencia NMC (2021): Blood lactate concentration and heart rates of Colombian Paso horses during field exercise test. Veterinary and animal science 8:(13) https://pubmed.ncbi.nlm.nih.gov/34189341/ 13/03/2022

Ok-Deuk K, Park YS Effect of age on heart rate blood lactate concentration packed cell volume and haemoglobin to exercise in Jeju crossbred horses. Journal of animal science and technology https://pubmed.ncbi.nlm.nih.gov/28138395/ 13/03/2022

Bayly WM, Franklin SH, VAN ERCK-WESTERGREN E.(2012) Equine veterinary journal

Boshuisen BL,.Delesalle C,de Bruijn M, de Mare, de Meeus C, B., Plancke L(2017) equine veterinary journal

Veterian key, cardiac response to exercise and training. https://veteriankey.com/cardiac-responses-to-exercise-and-training/ 30/04/2022.

Pictures taken by Celine Abela, Werner Bouwer.