The Science of Training Horses for Health and Performance
Dr David Marlin
The horse is a truly amazing and unique animal. Horses exist in both some of the hottest and some of the coldest locations on the planet. No other animal can attain speeds of over 40mph carrying a human on its back. The range of activities that horses can perform, from dressage, to jumping, to pulling, to racing over both short and long distances is also remarkable. However, for the horse to undertake these different activities, training which develops physical fitness and or skill is employed. Training increases capacity for exercise and hence performance and in theory should reduce the risk of injury. When it comes to trying to understand the horse, exercise, training and fitness, inevitably comparisons are often made with human sport and exercise physiology. However, this can be misleading. Horses are precocious; the foal is often able to stand and canter with it’s a mother within hours of birth. An ability linked to being able to survive in the wild. There is no doubt that effective training is one of the main factors in performance but numerous studies have demonstrated that the risk of injury to horses in training in all disciplines is very high. A better understanding of the science of training may help us to identify strategies that reduce this risk.
What is training?
Training can be physical, that is increasing the capacity for exercise or the ease with which a horse can exercise by increasing muscle strength or muscle endurance. However, not all training is “physical”. When we train horses to jump or to learn new movements this often may not affect the horse physically and the improvement may simply come as a result of the horse “learning” or practising the skill.
Training is repeated episodes or bouts of exercise that have a cumulative effect on a horse’s physical and or mental capacity for exercise. Improvement in the physical capacity for exercise is referred to as an increase in fitness. A single piece of exercise has very little impact on a horse’s fitness. It is the combined effect of many repeated exercise sessions that produce a training effect and an increase in fitness.
We can think of two types of training that we perform with horses. Physical training makes exercise easier for the horse or allows the horse to exercise for longer or allows a horse to run faster or jump higher or further or accelerate faster. These changes come about mainly because with training the locomotory (movement) muscles and the heart (which is also made of a special type of muscle) have a tremendous capacity to change and adapt to repeated bout of exercise.
The other type of training we commonly undertake with horses is focussed more on improving skill and modifying behaviour. Training a horse to load into a trailer or to stand when we mount into the saddle are examples of behavioural training and do not involve any physical changes in the horse’s body. Training a horse to perform dressage movements is primarily skill training but may also have a small physical training component as well. Whilst we are teaching the horse how to perform these movements (the skill training) we may also get some development of the muscles involved in making these movements (physical training).
What is the difference between exercise and training?
We use repeated bouts of exercise to increase fitness. Any activity that increases the metabolic activity of muscles (increases the rate at which they are using energy) can be considered to constitute exercise. This results in other changes in the horse’s body including increases in breathing rate and depth and heart rate. These changes occur to help transport more oxygen to the muscles and to remove heat and waste products such as carbon dioxide and lactic acid. Exercise always uses up energy, but does not always result in an increase in fitness.
Why is training horses apparently associated with a high risk of injury?
An important factor to bear in mind when considering why horses are prone to injury is that in the wild the volume and type of exercise that horses undertake is considerably different to that we impose when preparing (training) horses for competition. Studies have shown that wild horses spend longer periods walking and very little time in trot, canter and gallop. In addition, the bone, joint, tendon, ligament and muscle in the limbs of a 500kg horse have evolved to accommodate the weight of a 500kg horse. The addition of an 80kg rider and associated tack increases the weight the lower limbs must carry by 16%. Given that the weight bearing structures are not “designed” with a large safety margin, any additional weight is likely to increase the risk of damage and ultimately, failure. Similarly, whilst horses can and do jump in the wild, the frequency with which we jump horses in training and competing in disciplines such as show jumping and eventing far exceeds what they would undertake in the wild. The bottom line is that horses can carry a rider with a saddle but were NOT designed to do so. Horses can be trained to compete in diverse disciplines such as racing, endurance, dressage, driving and jumping but again were NOT designed to do so.
Another factor which might help explain the high prevalence of musculo-skeletal injury is that effective training to race or compete results in adaptation of different organs and tissues. Not all systems though have the same capacity to adapt. For example, training may result in an increase in ability of muscles to use oxygen (aerobic training; in longer distances race and endurance, for example) or an increase in muscle size and strength (e.g. in show-jumping). The respiratory system on the other hand does not change with training. The heart, which is a specialised muscle, can also undergo significant adaptation with training, with increases in size and or thickness of the muscular walls, particularly of the ventricles. Bone also responds to increased loading by laying down more bone to increase bone strength. Tendons, cartilage and ligaments on the other hand have very limited capacity to adapt to training.
So there is a conflict in training. The heart and muscles need prolonged periods of regular exercise to induce adaptation. In contrast, bone only needs very small amounts of loading to induce adaptation. The respiratory system, tendons, cartilage and ligaments essentially need no training and in fact are likely to suffer damage from training. Thus, there is a conflict; appropriate training for muscles and heart is likely to cause damage to tissues such as bone, cartilage, ligament and tendon. Why? Because horses evolved as grazers, to walk long distances and to have the ability to occasionally sprint flat out for short periods to escape predators. The fact that the horse is willing to be ridden and highly adaptable to a range of tasks may well help explain why we struggle with such a high prevalence of injury. This does not mean that we should not ride horses but it may help explain how we can better train them physically.
How important is training to performance?
When it comes to skill, training is extremely important and makes an enormous difference to performance. When it comes to activities which rely more on physical prowess than skill (endurance racing, flat racing) training and increase in fitness may account for perhaps a 10% improvement in performance but most of the difference between individual horses that have been trained will be down to genetic makeup.
How much science is there on the training of horses?
It may come as a surprise that there is a relatively small amount of good scientific studies related to the training of horses, specifically studies which investigate the differences between different training techniques; e.g. interval training versus conventional training. This is in contrast to the much greater number of studies looking at the training of people. Why are there so few studies? Training studies with horses are expensive. Relatively large numbers of horses are required to achieve statistically relevant results and to account for the inevitable loss of horses due to injury during such studies. For this very reason, many older training studies which are in the scientific literature are now considered to be of questionable significance because of small numbers and what we refer to as “lacking sufficient power”. In simple terms this means that conclusions we may have drawn on a study with 6 horses when first performed 20 years ago may no longer be considered safe!
How well do we train horses?
The answer is possibly not as well as we could. Orthopaedic injury is prevalent amongst almost all race and competition horse populations. Musculoskeletal injuries (MSI) are one of, if not the most common causes of morbidity and mortality in the sport or racing horse population. For example, in Sweden Wallin et al. (2000) and Egenval et al. (2006) reported that between 55 and 70% of all mortality was related to MSI. In the UK, in horses 15 years or older, the most common reason for euthanasia was because of lameness (24%)(Ireland et al. 2011). Because of the prevalence and economic impact MSI has been studied most frequently in racing populations (i.e. Thoroughbred, Standardbred and Quarter Horse racing) and other high intensity/high risk equestrian disciplines, such as polo, eventing and show jumping. In a study of 263 elite show jumpers from thirty-one riders and 39,028 days at risk, there were 2357 (6.0%) non-training or competing days in 126 horses. Non-acute orthopaedic injuries accounted for 55% of lost days and 22% due to acute orthopaedic injuries (Egenval et al. 2013). In a study of event horses and ponies, 56% of horses and 66% of ponies withdrawn from selection due to locomotor injury (Munsters et al. 2013). Singer et al. (2008) reported that 21% of horses intending to be competed in a Federation Equestre Internationale (FEI) Concours Complet International (CCI) eventing competition did not start due to injury and that 43% of these injuries involved soft tissues.
A potentially worrying observation is that despite advances in veterinary medicine, nutrition, technology and track surfaces orthopaedic injury is still prevalent. A number of studies suggest in fact that the frequency of injury in some horse populations has changed little over 30 years. In this time there has been a huge increase in knowledge through scientific study and many studies have identified risk factors for injury and it may therefore the high rate of injury may represent a failure of the science to be communicated to the wider horse population.
Why might apparent rates of injury to horses in training be unchanged or increasing?
• Horses are being trained harder
• Competitions have become more demanding
• Horses are being competed more frequently
• Breeding for performance has resulted in “weaker” horses
• Diagnosis is better: more and new conditions are being diagnosed
• Inappropriate training
• Misconceptions about what is good practice – too many “experts”; too much information available which is difficult to filter
• Change in horse owner demographic – more riders not from “traditional” horse backgrounds (e.g. Pony Club, Hunting, etc)
• Failure of scientists and vets to communicate new information
• Practices that reduce injury may reduce performance and are therefore rejected
• Riders are getting heavier
Application of science (principles and published studies) to training of horses in order to maximise performance and minimise injury
Whilst the convention of training 6 days a week Monday to Saturday with a Sunday off or training at weekends and training constantly week to week is frequently applied to horses, this possibly detrimental. In training human athletes 2-3 weeks training may be followed by a week of training at a reduced intensity to allow sub-clinical injury/damage to repair. This can even be extended into the training week. For example, training Saturday and Sunday, followed by Monday turn-out, Tuesday, Wednesday and Thursday training, Friday turnout. Unfortunately training of horses is often based around work, staff and social demands as opposed to what may be best for horses.
The most appropriate way to set the training intensity and to monitor changes in fitness is by using a heart rate monitor, particularly for disciplines requiring a high level of aerobic fitness such as endurance, racing, eventing and carriage driving. However, heart rate may also be useful in disciplines with a high anaerobic component as a recent study of heart rate in show-jumpers demonstrated an association between horses with higher heart rates and a higher number of faults (Harris et al. 2014). The importance of understanding training load was demonstrated by a study on Australian event horses being prepared for competition. The authors of this study measured heart rates during training and competition (Serrano et al. 2002). Only 1 horse was found to have been trained at the heart rates it reached during competition. The implication is that the other horses were trained at too low an intensity and were thus not fit enough for the competition. Training load should be increased gradually. For example, it is unwise to increase both speed and distance/duration at the same time. For horses that are being exercised 3-5 times a week, the training load should be increased approximately every 2-3 weeks.
Use of Tapering
The risk of horses becoming lame as competitions approach is very high. This may in part at least be due to increased frequency and intensity of training due to rider anxiety. At least one formal study has demonstrated that tapering (reducing duration of daily exercise but maintaining the intensity) in the 7 day period leading into competition actually enhances performance (Shearman et al, 2002).
Use of ice
Whilst techniques to reduce lower limb temperature such as cold-hosing, ice boots and coolant circulating systems are commonly used with horses during competition and training there appears to be little science as to the benefits of such management. Whilst the author personally recommends the use of cooling after moderate to intense training sessions or competition, some research is required in this area.
On the basis that bone, cartilage and tendon are frequently injured, and that bone only needs short periods of daily loading in order to adapt appropriately there would appear to be little benefit and in fact detriment, to long periods of trotting (>5 min) on hard surfaces (i.e. road work). However this is another area that needs further study.
Rider:Horse weight ratio
On the basis that the joints, tendons, ligaments and bone of a horse have evolved to carry its own body-weight and not that of itself and a rider and saddle and tack, in theory the greater the additional weight carried the greater the forces through the limbs potentially the greater the risk of injury. For example, Clayton et al. (1999) demonstrated that in trot the vertical force through both the fore and hind limbs was increased by the presence of a rider compared with trotting in hand. Clayton (1997) also demonstrated that added weight in show jumping also increased the maximal extension of both the fetlock and carpal joints on landing. There is only one unpublished scientific study that the author is aware of which suggests that rider weight may increase the risk of injury. This was carried out by a group of researchers at the Equine Research Centre, California State Polytechnic University, Pomona in California. They studied the relationship between rider and horse weights at the Tevis Cup endurance race in 1995 and 1996. Horses that were eliminated for lameness metabolic reasons were on average carrying a higher % of their bodyweight than horses that finished. But what is an appropriate weight? (In fact, the maximum weight a horse should carry is probably better described by the cross-sectional area of bone and joints but we will use weight as a surrogate of this). In the authors personal opinion weight carriage above 15% of the horses’ bodyweight is undesirable, particularly for disciplines involving high speed and or jumping.
The role of training surfaces in reducing or predisposing to lameness has been an area that has received some attention. Murray et al. (2010) found that arenas that became deep when wet and sand-based arenas increased the risk of lameness. In Thoroughbred racing, hard surfaces have been identified as an increased risk factor for fatality (Henley et al. 2006). For show-jumpers, training on sand-wood surfaces appeared to reduce the risk of lameness (Egenvall et al. 2013).
Training of horses, both with respect to skill and physical fitness, is required in order to maximise performance and if undertaken appropriately should reduce the risk of injury in competition, compared with the untrained horse. However, the prevalence of injury in horses during training is high. There are likely many contributing factors, of which many may not be readily modifiable or manageable. Some factors may still remain to be identified, for example genetic predisposition. However, there is clearly a large amount of scientific information of which a considerable amount has identified practices that may either increase or reduce the risk of injury during training. The task for scientific experts within the field should be to produce a consensus statement on current best practice in training of horses which could be widely disseminated throughout the horse industry. This may help to counteract the large volume of unsupported opinion that exists online and contribute long term to reducing injury and improving welfare.
1) The goal of training is to improve skill, performance and to reduce the risk of injury
2) There is a relatively limited amount of good scientific studies on the training of horses
3) Many horses are overloaded in training leading to injury
4) The most common injuries are orthopaedic and occur during training as opposed to during competition
5) Injuries most frequently occur to the legs
6) Horses do not always respond in the same way as human athletes
7) Training load should be increased gradually
8) Horses need periods of time to recover physically and possibly even mentally in training
9) Many horses are not adequately prepared for the demands of competition
10) Physical training programmes are often ineffective as the frequency or intensity of the training is inappropriate (too low an intensity; too long a duration; not repeated frequently enough)