Soundness and quality of performance are the main reasons of creating a synthetic training surface. Holt (2013) suggests that a synthetic surface which is inadequately constructed is widely seen to be documented as a risk factor to the soundness of the horse. Hobbs et al (2012) reported that there is an increasing requirement for training and competition surfaces. With so many surfaces required for different needs, it makes it challenging to produce surfaces that improve soundness of the horse, which is supported by Hernlund (2016) this shows an area in need of expanding in academic knowledge.
The central aim of this scientific review is to investigate the effects of surfaces on the performance of the horse. It will pinpoint the crucial differences between all-weather waxed and crushed sand surfaces to determine which surface best suits the needs of the training and competition riding. A discussion on injuries is documented along with the interactions between hoof and surface. This will better the understanding of what causes injuries.
All weather surfaces can be a tedious commitment for owners, but are fundamental due to increased road traffic and inflation of the horse riding population as described by Bromiley and Slattery, (2007). Synthetic surfaces are used for a range of different disciplines and are expected to promote both performance and soundness of the horse according to FEI (2017). The first synthetic race track was constructed by Meadows Racetrack in Pennsylvania 1963 Equestriansurfaces.com (2017) which suggests sixty years of research done into synthetic surfaces.
Varying types of surface and firmness of surfaces are needed for different disciplines. Murray et al (2010) suggested a consistent surface could protect dressage horses from lameness. Dressage requires lower loading rates on the limbs than those needed for show jumping because show jumping involves speed and agility as Hobbs et al., (2012) claims. It is important to remember that jumping takes place on both artificial surfaces and grass whereas dressage takes place on synthetic surfaces stated Egenvall et al (2013).
Synthetic surfaces can range from silica sand, crushed sand, wax-coated sand, grass, polyvinyl chloride (PVC), woodchip, rubber and fiber additives. Crushed sand is made by grinding rock to make more cornered granules as Stavermann and Hernlund, (2017) describes.
Hobbs et al., (2012) explain how riders and trainers expect training facilities and surfaces at competitions to be well maintained and safe for their horse. However, there are no regulations or systems currently in place to produce this level of standards. This highlights the lack of guidelines in this area and shows a weak point in knowledge of owners and trainers about training surfaces.
All-weather Waxed Compared with Crushed sand surface
Each surface houses its own associated problems. Sand surfaces are a more traditional surface choice and are popular with riders. Martin Collins, (2017) advises that sand surfaces can be difficult to manage because they are strongly affected by weather conditions and changes in moisture content. If the surface is not maintained frequently, horses will be at an increased risk of soft tissue damage. Whilst, all-weather waxed surfaces are thought to have more resilience, require minimal maintenance and are particularly designed for National Hunt horses according to Andrewsbowen.co.uk, (2017) this implies that all-weather waxed tracks have more support due to being the choice for race horses.
Martincollins.com, (2017) suggest that waxed tracks can function in temperatures of -12 to + 40 Celsius which could be a reason for their increasing popularity. On the other hand, Martin Collins, (2017) implies that waxed tracks are the popular choice due to competing and the long lasting all-weather reasons. However waxed surfaces are said on average to cost £20,000 for a 20x40m school which could be an expensive responsibility if the horse becomes injured.
In a preliminary study on dressage horses by Murray et al., (2010), results showed that lameness was increased when the horse was trained on sand although, the more frequently the horse was trained on the surface, the lower the risk of lameness. This implies that the horses musculoskeletal system achieves adaptations to this surface over time. However this does not mean that training on one surface is the best solution in preventing distal limb injuries. It was also found the all-weather waxed track has a more progressive super digital flexor tendon (SDFT) loading than crushed sand according to Crevier-Denoix et al (2009) which is a positive aspect however loading patterns showed proximal interphalangeal joint movements during the loading phase. This could be due to the fact that the sand track provides less cushioning which in turn puts more stress on tendons and ligaments during the loading phase.
Similarly, Chateau et al., (2009) found that deceleration and vibration of the hoof at impact were lower on a waxed compared to sand, which suggests greater shock absorption of the waxed track and more rigidity of the sand. This could also be due to the deepness and weather conditions that the sand is so easily affected by.
Furthermore, in a similar study by Robin et al (2009) results suggested that the extent of the braking force on the waxed track was considerably lower in comparison to the sand track. This shows a less strain on the horse’s distal limb because there are fewer forces applied.
The majority of the research that has been found concludes that the all-weather waxed surface had the properties of a better surface for the performance of the horse. However there is no evidence yet to suggest that it improves the soundness of the horse. In the recent comparative studies, braking and loading forces show more concussive forces in crushed sand track. A hoof and surface comparison and better insight into injuries is needed to make conclusions as to which surface is best suited to the soundness and performance of the horse.
Surface and hoof interaction
Extrinsic factors interact with the intrinsic factors to affect the performance of the horse as Hobbs et al., (2012) claim. This suggests a crucial link between hoof and surface. Clayton (2017) states that interpreting the motion of the horses stride in terms of timing and distance is known as kinematic analysis. Thomason and Peterson, (2008) add to this idea when demonstrating that kinematics display forces and energies that are involved with the disshapement of the horses foot. Chateau et al., (2009) claim a way of measuring this is using ground reaction force (GRF) which is a method to research the interaction between the hoof and the ground. Robin et al (2009) describes GRF as interesting method of evaluating this interation.
GRF are transferred through the foot to the entire limb. Kinetic analysis is the external and internal forces involved with this foot and surface interaction. Three dynamometric horse shoes are an invention used in recent research to analyze kinematics and mediolateral balance and forces on different surfaces as Chateau et al (2009) and Robin et al (2009) demonstrate. In horse racing it has been reported that More than 9 kN of force is applied during each stride to the contact area of the hoof according to Peterson, McIlwraith and Reiser, (2008). Each stride has three main phases including the landing, loading and rollover push-off phase.
Landing/ braking phase
During the landing phase, ‘Energy enters the locomotor system when the foot strikes the ground’ as Clayton (2017) states. Due to only the hoof and pastern being involved in this phase, forces on the foot are fairly low as Peterson (2012) explains. Injury in the loading phase often affects the distal limb as Herlund (2014) claims. Which suggests that there should be give in the surface to lessen the impact on the distal limb.
Loading/ stance/ support phase
Throughout loading, the hoof changes shape a great deal. Johnston and Back, (2006) describe the loading phase as ‘a period of spatial stability of the hoof’. Initially, is has been described that the distal phalanx causes the dorsal hoof wall to move caudally ventrally and this pushes the quarters out, resulting in an expansion in the bulbs as described by Thomason et al (2002). The loading phase has impact on the orthopedic wellbeing of the horse according to Johnston and Back, (2006) and this is supported by Crevier-Denoix et al (2013) who reported that the placement of the hoof during loading is important for our understanding of the musculoskeletal movement of the horse. This is because of the hight injury risk during this phase. Chateau et al (2009) suggests that the injury risk in this phase mainly affects the tendons and ligaments which can be a result of months of box rest hindering performance. Figure 2 demonstrates the flexor tendons and suspensories under strain when under stress from the weight of the horse and rider. A surface could affect this stage if it were too hard or soft.
Rollover push-off/ take-off phase
This phase loads the ligaments, the hoof wall and the tip of the coffin bone and there is an eventual stress on the superficial digital flexor tendon. Johnston and Back, (2006) describe how the distal limb stores and releases energy through the recoiling of the tendons. The hoof and leg propel forward involuntarily due to the release stored energy as Herlund (2014) suggests. Figure 3 shows the rotation of the heel off the surface rolling over the toe to push off stage into the next stride.
Investigating the forces that are propelled between the horse and surface gives more knowledge about what may affect the performance of the horse. This understanding gives clues as to how a surface can be seen as a risk factor to the performance of the horse.
Softer surfaces in coparison with Harder surfaces and the affects on the horse
Recent research shows that there is dispute about whether it is best for the performance of the horse to use a hard or a soft surface. Brosnan et al., (2009) state that for surfaces, hardness is often measured with a traditional method called the Clegg hammer where the ‘maximum vertical deceleration upon impact is measured using a known mass and drop height. The following section defines how a softer surface and a firmer surface may affect the horse in terms of locomotion and injury.
A softer looser surface can absorb shock well but lack support. Murray (2012) shows that when the horse’s limb feels unbalanced, the horse may use another limb for stabilization. However this in turn can over extend the heel or toe, damaging the supporting tendons and ligaments. Premierequestrian.com (2017) Suggest ‘A deep, dead surface rebounds energy too slowly. The horse works harder on a softer surface resulting in muscles and respiration becoming fatigued. Additionally, Clayton (2017) states that when a horse is working on a softer surface, stress in the deep digital flexor tendon and navicular ligaments is decreased when the toe is able to rotate into the surface. This can be beneficial for horses with navicular because the navicular area is not under so much stress resulting in reduction of pain in the navicular area.
In a study by Crevier-Denoix et al (2009), results suggested that softer racing surfaces were also associated with fewer fatalities and injuries than harder surfaces. This could be because softer surfaces may be able to aid in cushioning to the excessive forces placed upon the horses musculoskeletal system at high speed.
A harder surface however, does not aid in providing impact shock. A stiff and compacted surface recoils energy back to the surface too quickly, causing additional shock and vibrations to be absorbed by the horse as premierequestrian.com (2017) claim. Over time these forces can reduce the horses performance and sometimes the damage is irreversible.
It has been recognized that a surface that is said to have a greater braking effect or ‘grip’ tends to have more forces on the limb Equestriansurfaces.com (2017). This is seen to have a negative effect on the horse long term because as Clayton (2017) suggests, a surface with less pliability can lead to microtrauma to bone and articular cartilage and result in chronic bone and articular problems which will lead to loss of support in the framework and leverage system as supported by Bromiley and Slattery (2007).
Additionally, foot soreness and concussive injuries have been strongly correlated to riding show jumpers on hard ground Hobbs et al., (2012). This could be because show jumpers are competed on hard surfaces at shows after training on a softer surface at home. Foot soreness and concussive injuries have been strongly correlated to riding show jumpers on hard ground Hobbs et al., (2012). According to Premierequestrian.com (2017), a hard surface does not allow the frog to have adequate contact with the ground which obstruct blow flow to the hoof capsule and can lead to navicular and laminitis.
We can gather that both hard and soft surfaces have consequences on the health of the horse. According to Premierequestrian.com (2017) a good surface however, will return forces to the horses limbs at the same rate they were applied. It lowers the energy that the horse needs to work increasing performance quality. Spending more money on a proper surface may be beneficial in the long run. The affects of surfaces on the musculoskeletal system of the horse are important to understand to prevent injury and months of rehabilitation.
Injuries to the horse due to Poor surfaces
Short term effects
Short term effects could cause injuries when competing. Bromiley and Slattery (2007) reported a rise in the amount of injuries when human athletes train on one surface then compete on another and urges that this should be considered by owners when competing or having lessons at different yards when only training on one surface. This is because sudden changes in surface can cause the muscles to fatigue.
Injury on race tracks has been well documented. Parkin et al., (2010) found that in UK racehorses, distal limb fractures are the most common cause of equine fatality. Similarly, Crevier-Denoix et al., (2013) reported that synthetic surfaces could lead to ‘new types of nonfatal injuries’ associated with soft tissue or hind limb lameness. The Jockey Club conducted a 3 year surveillance study (1996–1998) into racing injuries and surfaces. 2358 clinical events were recorded. 1937 involved the musculoskeletal system and 421 involved other body systems. 81%of limb injury reports involved forelimbs and 46% involved flexor tendon and suspensory ligaments. This suggests the surface may have been to hard because the tendon that were affected were on the palmer side of the limb.
In a field study by Egenvall et al (2013) the aim was ‘to associate ‘days-lost to training’ in elite-level show-jumpers to horse characteristics and the time spent working on various training and competition surfaces.’ Of these, 2357 (6.0%) were days-lost and 22% of these were due to non-acute and acute orthopedic injuries demonstrating the fact that show jumpers must have enough cushioning for their footing especially after a jump otherwise the concussive forces can cause long term and short term effects.
Long term effects
Chateau et al (2010) suggests that the distal limbs must deal with excessive amounts of vibrations, shock. Long term affects on the horse may cause chronic pain. Chronic exposure to impact has been linked to degeneration of articular cartilage and subchondral bone damage stated Chateau et al (2009). Whilst Johnston and Back, (2006) claim that lameness is often the result of irreversible damage to vital tissues. The bones, joints, ligaments and muscles adapt to the training conditions to which they are exposed according to Bromiley and Slattery, (2007). Adaptations to the musculoskeletal system can take weeks or even months suggests the FEI (2014). Thus, it is important for the horse to be trained on a variety of surfaces in order to condition bone, ligaments and tendons.
Discussion On the effects on the horse
This shows the importance of the depth of knowledge of training surfaces for both performance and welfare reasons. The body of research to date is mainly based upon risk factors associated with surfaces Hobbs et al (2012). The research into different short term injuries due to surface types seems to be a growing field. However it seems that there is still much to be investigated especially in disciplines such as cross country and eventing. However it can be concluded that the majority of injuries seen due to inadequate surface types are involving the soft tissues in the horse’s distal limbs. This suggests that it is mainly due to lack of maintenance or precision when constructing these surfaces because the majority of injuries are because of strains and tears which imply that the horse is made to over compensate, flex or extend. However most long term effects are due to the excessive forces on the horses limbs over time and effect cartilage and bones causing degenerative problems.
Variation is said to decrease the risk of injury both long term and short term through training intensity and the use of different surfaces Equestrian Surfaces- A Guide, (2017). Ensuring that training regimes change gradually should allow for adaption to the musculoskeletal system especially to prevent injury in both the short term and long term.
Recent research suggests that a surface that is too hard or soft can be detrimental to the horse. Creating the perfect surface seems to be unachievable. This is because even the ideal surface can be used incorrectly. Herlund, (2014) supports this idea that the risk of injury is affected by how the surface is used. Therefore the type of surface that best promotes the soundness and performance of the horse must be used and maintained correctly, eg- allowing gradual changes in the horses work to allow for physical adaptations. Without this, any surface will be detrimental to the horse.
However in the general population disciplines prefer to use a softer surface because injuries tend to be less common than those on harder surfaces Additionally owners tend to feel the work ‘cushioning’ comforting when constructing a surface for their horse. With soundness and performance in mind a slightly softer surface will cause less injuries and long term effects on the horse. This supports the idea that the all-weather waxed surface is more ideal than the crushed sand because the all-weather waxed track is designed to have more cushioning and is specifically designed for performance reasons. Therefore this surface seems to promote both performance and soundness of the horse.
List of Figures
Figure 1: Horse racing on a synthetic track. Source: Horsefund.org (2017)
Figure 2: Shows how the bones collide from concussive forces. Source: Premierequestrian.com, (2017).
Figure 3: Shows the flexor tendons and suspensories absorbing the shock of the weight of horse and rider. Source: Premierequestrian.com, (2017)
Figure 4: Shows the rotation of the heel off the surface rolling over the toe to push off stage into the next stride. Source: Premierequestrian.com, (2017).
Figure 5: A diagram demonstrating the impact of a hard or soft surface on the horse’s limbs. Source: Premierequestrian.com, (2017)
Figure 6: A diagram showing how ‘cushioning’ reduces impact during the loading phase. Source: Equestrian Surfaces- A Guide, (2017)
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