Relationships between hoof-acceleration patterns of galloping horses and dynamic properties of the track

Timing Differences in Stride Cycle Phases in Retired Racehorses Ridden in Rising and Two-Point Seat Positions at Trot on Turf, Artificial and Tarmac Surfaces

Injuries to racehorses and their jockeys are not limited to the racetrack and high-speed work. To optimise racehorse-jockey dyads' health, well-being, and safety, it is important to understand their kinematics under the various exercise conditions they are exposed to. This includes trot work on roads, turf and artificial surfaces when accessing gallop tracks and warming up. This study quantified the forelimb hoof kinematics of racehorses trotting over tarmac, turf and artificial surfaces as their jockey adopted rising and two-point seat positions. A convenience sample of six horses was recruited from the British Racing School, Newmarket, and the horses were all ridden by the same jockey. Inertial measurement units (HoofBeat) were secured to the forelimb hooves of the horses and enabled landing, mid-stance, breakover, swing and stride durations, plus stride length, to be quantified via an in-built algorithm. Data were collected at a frequency of 1140 Hz. Linear Mixed Models were used to test for significant differences in the timing of these stride phases and stride length amongst the different surface and jockey positions. Speed was included as a covariate. Significance was set at p < 0.05. Hoof landing and mid-stance durations were negatively correlated, with approximately a 0.5 ms decrease in mid-stance duration for every 1 ms increase in landing duration (r2 = 0.5, p < 0.001). Hoof landing duration was significantly affected by surface (p < 0.001) and an interaction between jockey position and surface (p = 0.035). Landing duration was approximately 4.4 times shorter on tarmac compared to grass and artificial surfaces. Mid-stance duration was significantly affected by jockey position (p < 0.001) and surface (p = 0.001), speed (p < 0.001) and jockey position*speed (p < 0.001). Mean values for mid-stance increased by 13 ms with the jockey in the two-point seat position, and mid-stance was 19 ms longer on the tarmac than on the artificial surface. There was no significant difference in the breakover duration amongst surfaces or jockey positions (p ≥ 0.076) for the ridden dataset. However, the mean breakover duration on tarmac in the presence of a rider decreased by 21 ms compared to the in-hand dataset. Swing was significantly affected by surface (p = 0.039) and speed (p = 0.001), with a mean swing phase 20 ms longer on turf than on the artificial surface. Total stride duration was affected by surface only (p = 0.011). Tarmac was associated with a mean stride time that was significantly reduced, by 49 ms, compared to the turf, and this effect may be related to the shorter landing times on turf. Mean stride length was 14 cm shorter on tarmac than on grass, and stride length showed a strong positive correlation with speed, with a 71 cm increase in stride length for every 1 m s-1 increase in speed (r2 = 0.8, p < 0.001). In summary, this study demonstrated that the durations of the different stride cycle phases and stride length can be sensitive to surface type and jockey riding position. Further work is required to establish links between altered stride time variables and the risk of musculoskeletal injury.

Warm Season Turfgrass Equine Sports Surfaces: An Experimental Comparison of the Independence of Simple Measurements Used for Surface Characterization

Turfgrass in equine sports has clear advantages over other types of reinforcement but adds complexity to the management. This study investigates factors that influence the turfgrass' surface performance and how the use of a drainage package and a geotextile reinforcement affect quantitative measurements of turfgrass. The measurements are made using affordable, lightweight testing tools that are readily available or easily constructed. Eight boxes with turfgrass over a mix of the arena with peat at a consistent depth were tested for volumetric moisture content (VMC %) with time-domain reflectometry (TDR), the rotational peak shear device (RPS), the impact test device (ITD), soil cone penetrometer (SCP), and the Going Stick (GS). Results obtained using TDR, RPS, ITD, SCP, and GS indicate that the presence of the geotextile and drainage package was mainly detected by VMC (%), SCP detected geotextile addition, and GS detected the interaction of geotextile × drainage package. Linear regression showed SCP and GS are related to geotextile and was positively correlated between them and negatively with VMC (%). The testing showed some limitations of these devices, mainly related to moisture content and sod composition, but the potential exists to utilize these devices for quality control as well as for the monitoring of maintenance of the surfaces when controlling the range of both VMC (%) and sod constitution.

Hoof Impact and Foot-Off Accelerations in Galloping Thoroughbred Racehorses Trialling Eight Shoe-Surface Combinations

The athletic performance and safety of racehorses is influenced by hoof−surface interactions. This intervention study assessed the effect of eight horseshoe−surface combinations on hoof acceleration patterns at impact and foot-off in 13 galloping Thoroughbred racehorses retired from racing. Aluminium, barefoot, GluShu (aluminium−rubber composite) and steel shoeing conditions were trialled on turf and artificial (Martin Collins Activ-Track) surfaces. Shod conditions were applied across all four hooves. Tri-axial accelerometers (SlamStickX, range ±500 g, sampling rate 5000 Hz) were attached to the dorsal hoof wall (x: medio-lateral, medial = positive; y: along dorsal hoof wall, proximal = positive; and z: perpendicular to hoof wall, dorsal = positive). Linear mixed models assessed whether surface, shoeing condition or stride time influenced maximum (most positive) or minimum (most negative) accelerations in x, y and z directions, using ≥40,691 strides (significance at p < 0.05). Day and horse−rider pair were included as random factors, and stride time was included as a covariate. Collective mean accelerations across x, y and z axes were 22−98 g at impact and 17−89 g at foot-off. The mean stride time was 0.48 ± 0.07 s (mean ±2 SD). Impact accelerations were larger on turf in all directions for forelimbs and hindlimbs (p ≤ 0.015), with the exception of the forelimb z-minimum, and in absolute terms, maximum values were typically double the minimum values. The surface type affected all foot-off accelerations (p ≤ 0.022), with the exception of the hindlimb x-maximum; for example, there was an average increase of 17% in z-maximum across limbs on the artificial track. The shoeing condition influenced all impact and foot-off accelerations in the forelimb and hindlimb datasets (p ≤ 0.024), with the exception of the hindlimb impact y-maximum. Barefoot hooves generally experienced the lowest accelerations. The stride time affected all impact and foot-off accelerations (p < 0.001). Identifying factors influencing hoof vibrations upon landing and hoof motion during propulsion bears implication for injury risk and racing outcomes.

The effect of horseshoes and surfaces on horse and jockey centre of mass displacements at gallop

Horseshoes influence how horses' hooves interact with different ground surfaces, during the impact, loading and push-off phases of a stride cycle. Consequently, they impact on the biomechanics of horses' proximal limb segments and upper body. By implication, different shoe and surface combinations could drive changes in the magnitude and stability of movement patterns in horse-jockey dyads. This study aimed to quantify centre of mass (COM) displacements in horse-jockey dyads galloping on turf and artificial tracks in four shoeing conditions: 1) aluminium; 2) barefoot; 3) GluShu; and 4) steel. Thirteen retired racehorses and two jockeys at the British Racing School were recruited for this intervention study. Tri-axial acceleration data were collected close to the COM for the horse (girth) and jockey (kidney-belt), using iPhones (Apple Inc.) equipped with an iOS app (SensorLog, sample rate = 50 Hz). Shoe-surface combinations were tested in a randomized order and horse-jockey pairings remained constant. Tri-axial acceleration data from gallop runs were filtered using bandpass Butterworth filters with cut-off frequencies of 15 Hz and 1 Hz, then integrated for displacement using Matlab. Peak displacement was assessed in both directions (positive 'maxima', negative 'minima') along the cranio-caudal (CC, positive = forwards), medio-lateral (ML, positive = right) and dorso-ventral (DV, positive = up) axes for all strides with frequency ≥2 Hz (mean = 2.06 Hz). Linear mixed-models determined whether surfaces, shoes or shoe-surface interactions (fixed factors) significantly affected the displacement patterns observed, with day, run and horse-jockey pairs included as random factors; significance was set at p<0.05. Data indicated that surface-type significantly affected peak COM displacements in all directions for the horse (p<0.0005) and for all directions (p≤0.008) but forwards in the jockey. The largest differences were observed in the DV-axis, with an additional 5.7 mm and 2.5 mm of downwards displacement for the horse and jockey, respectively, on the artificial surface. Shoeing condition significantly affected all displacement parameters except ML-axis minima for the horse (p≤0.007), and all displacement parameters for the jockey (p<0.0005). Absolute differences were again largest vertically, with notable similarities amongst displacements from barefoot and aluminium trials compared to GluShu and steel. Shoe-surface interactions affected all but CC-axis minima for the jockey (p≤0.002), but only the ML-axis minima and maxima and DV-axis maxima for the horse (p≤0.008). The results support the idea that hoof-surface interface interventions can significantly affect horse and jockey upper-body displacements. Greater sink of hooves on impact, combined with increased push-off during the propulsive phase, could explain the higher vertical displacements on the artificial track. Variations in distal limb mass associated with shoe-type may drive compensatory COM displacements to minimize the energetic cost of movement. The artificial surface and steel shoes provoked the least CC-axis movement of the jockey, so may promote greatest stability. However, differences between horse and jockey mean displacements indicated DV-axis and CC-axis offsets with compensatory increases and decreases, suggesting the dyad might operate within displacement limits to maintain stability. Further work is needed to relate COM displacements to hoof kinematics and to determine whether there is an optimum configuration of COM displacement to optimise performance and minimise injury.

An Experimental Comparison of Simple Measurements Used for the Characterization of Sand Equestrian Surfaces

Simple Summary

Consistency of equestrian surfaces can contribute to safety and performance. An optimal surface is influenced by the design and material selection as well as maintenance and climate. To improve surfaces the quantitative testing of functional surface properties must expand beyond the current testing at the highest levels of competition. More widespread quantitative measurements would have a positive influence on animal welfare and rider safety. To expand beyond the current top levels of the sport, simple tools are required that can be shown to detect relevant changes in construction and maintenance. Our work suggests that the appropriate use of simple devices can help with both quality control of new surfaces and the monitoring of existing surfaces. Performance modifications to the layered surface design and addition of Geotextile were detected using the Going Stick and a simple impact test. These measured results are also influenced by other factors related to the surface condition such as moisture. Caution must be exercised in the interpretation of the results since these tools have not been demonstrated to correlate to either performance or safety of the surface. However, these results are encouraging and provide a justification for future development of this type of equipment.

Abstract

Quantitative measurements of performance parameters have the potential to increase consistency and enhance performance of the surfaces as well as to contribute to the safety of horses and riders. This study investigates how factors known to influence the performance of the surface, incorporation of a drainage package, control of the moisture control, and introduction of a geotextile reinforcement, affect quantitative measurements of arena materials. The measurements are made by using affordable lightweight testing tools which are readily available or easily constructed. Sixteen boxes with arena materials at a consistent depth were tested with the Going Stick (GS), both penetration resistance and shear, the impact test device (ITD), and the rotational peak shear device (RPS). Volumetric moisture content (VMC %) was also tested with time–domain reflectometry (TDR). Results obtained using GS, RPS, ITD, and TDR indicate that the presence of the drainage package, moisture content, and geotextile addition were detected. Alterations due to combinations of treatments could also be detected by GS, ITD, and TDR. While the testing showed some limitations of these devices, the potential exists to utilize them for quality control of new installations as well as for the monitoring of maintenance of the surfaces.

The Effect of Tungsten Road Nails on Upper Body Movement Asymmetry in Horses Trotting on Tarmac

Tungsten road nails are commonly used by farriers to increase grip between the hoof and the ground surface. There is limited evidence relating the use of road nails to the fundamental mechanics of movement. Grip is important for efficient deceleration on landing and subsequent propulsion, but this must be balanced against an amount of slip to divide the landing force into horizontal as well as vertical subcomponents. Here, we conducted an intervention study to quantify the effect of lateral heel road nail placement on weight bearing and propulsion in 10 horses trotting on tarmac. Wireless inertial measurement units measured vertical movement asymmetry. Differences in head and pelvic movement asymmetry before/after subsequent application of laterally placed road nails to forelimb and hindlimb hooves in a randomized order were compared to zero value (no change) with a one-sample t-test, P < .05. Left-to-right tuber coxae movement amplitude difference was significantly more negative (-3.25 mm, P = .03), suggesting more right than left tuber coxae movement amplitude, after application of a road nail to the left hindlimb. No movement asymmetries at the poll, withers, or sacrum were detected after nail placement (all P > .055). Pelvic movement indicates a very small increase in weight bearing and propulsion provided by the hindlimb with a laterally placed road nail compared to the contralateral hindlimb. Further work is needed to investigate slip- and grip-related parameters at the level of the hoof and to investigate the long-term consequences of very small changes in movement asymmetry.

Does 'hacking' surface type affect equine forelimb foot placement, movement symmetry or hoof impact deceleration during ridden walk and trot exercise?

BACKGROUND

Both pleasure and competition horses regularly exercise on surfaces such as tarmac, gravel and turf during 'hacking'. Despite this, there is limited evidence relating to the effect of these surfaces upon foot-surface interaction.

OBJECTIVES

To investigate forelimb foot placement, hoof vibration and movement symmetry in pleasure horses on three commonly encountered hacking surfaces.

STUDY DESIGN

Quantitative gait study in a convenience sample.

METHODS

Six horses regularly partaking in hacking exercise were ridden in walk and trot on all surfaces. Horses were equipped with one hoof-mounted, accelerometer and four body-mounted inertial measurement units (IMUs) to measure foot impact and movement symmetry. High-speed (400 FPS) video footage of foot-placement was acquired (dorsal, palmar, lateral views). Foot-impact and movement symmetry were analysed with a mixed effects model and Bowker symmetry tests for foot-placement analysis.

RESULTS

Vibration power and frequency parameters increase as perceived surface firmness increases from grass, to gravel, to tarmac (P≤0.001). Vibration power parameters were consistently greater at trot compared with walk (P≤0.001), but the same was not true for vibration frequency (P≥0.2). Greatest movement asymmetry was recorded during grass surface trotting. No significant difference in foot-placement was detected between the three surfaces.

MAIN LIMITATIONS

This was a field study using three commonly encountered hacking surfaces. Surface properties change easily with water content and temperature fluctuations so care must be taken when considering other similar surfaces, especially at different times of the year. Six leisure horses were used so the results may not be representative of horses of all types.

CONCLUSIONS

Vibration parameters generally increase as perceived surface firmness increases. Increasing speed alters vibration power but not frequency. Further investigations are required to determine the role that this may play in the development of musculoskeletal disease in horses.

Numerical time-domain modelling of hoof-ground interaction during the stance phase

BACKGROUND

Hoof-ground interaction impacts on the health and performance characteristics of horses. Due to complex interactions between hoof and ground during the stance phase, previous experimentally dominated studies concentrated on subproblems of the phenomena observed. A multidisciplinary methodology with mathematical modelling, material testing and in vivo experimental measurements seems promising.

OBJECTIVES

With the help of a mathematical approach, this contribution aims to explain from a biomechanical point of view the phenomena observed during experimental investigations (hoof acceleration, interacting forces) and aims to contribute to an overall experimental-mathematical multidisciplinary approach.

STUDY DESIGN

In silico modelling of hoof-ground interaction (limb, hoof and horizontally unbounded ground).

METHODS

Hoof-ground interaction is represented by a time-domain finite element model including the limb, the hoof and the unbounded representation of the ground via the scaled boundary finite element method to capture radiation damping during the stance phase. Motoric forces (driving forces) of the horse during locomotion are included.

RESULTS

Numerical model results for acceleration-time relations (hoof) at different trotting velocities are compared with previously published acceleration-time relations and show qualitative agreement. From the model approach, power loss due to different ground properties and ground damping is computed in combination with the maximum limb force during the stance phase.

MAIN LIMITATIONS

Intentionally, a simplified model approach for the material and structural representation of the limb, the hoof and the ground in terms of material features and spatial resolution has been used for this study, which might be the basis for a model refinement in terms of contact properties as well as the integration of bone and joint structures.

CONCLUSIONS

The comparison to experimentally obtained results demonstrates the applicability of the model, which, in turn, enables an insight into the processes taking place during hoof-ground interaction.

Modelling the effect of race surface and racehorse limb parameters on in silico fetlock motion and propensity for injury

BACKGROUND

The metacarpophalangeal joint (fetlock) is the most commonly affected site of racehorse injury, with multiple observed pathologies consistent with extreme fetlock dorsiflexion. Race surface mechanics affect musculoskeletal structure loading and injury risk because surface forces applied to the hoof affect limb motions. Race surface mechanics are a function of controllable factors. Thus, race surface design has the potential to reduce the incidence of musculoskeletal injury through modulation of limb motions. However, the relationship between race surface mechanics and racehorse limb motions is unknown.

OBJECTIVE

To determine the effect of changing race surface and racehorse limb model parameters on distal limb motions.

STUDY DESIGN

Sensitivity analysis of in silico fetlock motion to changes in race surface and racehorse limb parameters using a validated, integrated racehorse and race surface computational model.

METHODS

Fetlock motions were determined during gallop stance from simulations on virtual surfaces with differing average vertical stiffness, upper layer (e.g. cushion) depth and linear stiffness, horizontal friction, tendon and ligament mechanics, as well as fetlock position at heel strike.

RESULTS

Upper layer depth produced the greatest change in fetlock motion, with lesser depths yielding greater fetlock dorsiflexion. Lesser fetlock changes were observed for changes in lower layer (e.g. base or pad) mechanics (nonlinear), as well as palmar ligament and tendon stiffness. Horizontal friction and fetlock position contributed less than 1° change in fetlock motion.

MAIN LIMITATIONS

Simulated fetlock motions are specific to one horse's anatomy reflected in the computational model. Anatomical differences among horses may affect the magnitude of limb flexion, but will likely have similar limb motion responses to varied surface mechanics.

CONCLUSIONS

Race surface parameters affected by maintenance produced greater changes in fetlock motion than other parameters studied. Simulations can provide evidence to inform race surface design and management to reduce the incidence of injury.

The foot-surface interaction and its impact on musculoskeletal adaptation and injury risk in the horse

The equine limb has evolved for efficient locomotion and high-speed performance, with adaptations of bone, tendon and muscle. However, the system lacks the ability seen in some species to dynamically adapt to different circumstances. The mechanical interaction of the limb and the ground is influenced by internal and external factors including fore-hind mass distribution, lead limb, moving on a curve, shoeing and surface properties. It is unclear which of the components of limb loading have the largest effect on injury and performance but peak load, impact and vibration all play a role. Factors related to the foot-ground interface that limit performance are poorly understood. Peak performance varies vastly between disciplines but at high speeds such as racing and polo, force and grip are key limits to performance.

Discrimination of two equine racing surfaces based on forelimb dynamic and hoof kinematic variables at the canter

The type and condition of sport surfaces affect performance and can also be a risk factor for injury. Combining the use a 3-dimensional dynamometric horseshoe (DHS), an accelerometer and high-speed cameras, variables reflecting hoof-ground interaction and maximal limb loading can be measured. The aim of the present study was to compare the effects of two racing surfaces, turf and all-weather waxed (AWW), on the forelimbs of five horses at the canter. Vertical hoof velocity before impact was higher on AWW. Maximal deceleration at impact (vertical impact shock) was not significantly different between the two surfaces, whereas the corresponding vertical force peak at impact measured by the DHS was higher on turf. Low frequency (0-200 Hz) vibration energy was also higher on turf; however high frequency (>400 Hz) vibration energy tended to be higher on AWW. The maximal longitudinal force during braking and the maximal vertical force at mid-stance were lower on AWW and their times of occurrence were delayed. AWW was also characterised by larger slip distances and sink distances, both during braking and at maximal sink. On a given surface, no systematic association was found between maximal vertical force at mid-stance and either sink distance or vertical impact shock. This study confirms the damping properties of AWW, which appear to be more efficient for low frequency events. Given the biomechanical changes induced by equestrian surfaces, combining dynamic and kinematic approaches is strongly recommended for a reliable assessment of hoof-ground interaction and maximal limb loading.

Fatal musculoskeletal injuries of Quarter Horse racehorses: 314 cases (1990-2007)

OBJECTIVE

To determine major causes of death and the anatomic location of musculoskeletal injuries in Quarter Horse racehorses in California.

DESIGN

Retrospective case series.

ANIMALS

314 Quarter Horse racehorses with musculoskeletal injuries that were necropsied through the California Horse Racing Board Postmortem Program from 1990 to 2007.

PROCEDURES

Postmortem pathology reports were retrospectively reviewed. Musculoskeletal injuries were categorized by anatomic region and described. The number of Quarter Horse starts and starters for the same period of time were obtained from a commercial database for determination of fatal injury incidence.

RESULTS

Musculoskeletal injuries accounted for 314 of the 443 (71 %) Quarter Horse racehorses that died during the 18-year study period. Fatal musculoskeletal injuries occurred at a rate of 2.0 deaths/1,000 race starts and 18.6 deaths/1,000 horses that started a race. Musculoskeletal injuries occurred predominantly during racing (84%) and in the forelimbs (81%). The most common fatal musculoskeletal injuries were metacarpophalangeal and metatarsophalangeal joint (fetlock) support injuries (40%) and carpal (24%), vertebral (10%), and scapular (8%) fractures. Proximal interphalangeal (pastern) joint luxations resulted in death of 3% of horses. Fracture configurations of some bones were consistent with those of Thoroughbred racehorses. Evidence of preexisting stress remodeling of bone was reported for some fractures.

CONCLUSIONS AND CLINICAL RELEVANCE

Knowledge of common locations and types of fatal musculoskeletal injuries in racing Quarter Horses may enhance practitioners' ability to detect mild injuries early, rest horses, and help prevent catastrophic injuries.

Validation of a laboratory method for evaluating dynamic properties of reconstructed equine racetrack surfaces

Background

Racetrack surface is a risk factor for racehorse injuries and fatalities. Current research indicates that race surface mechanical properties may be influenced by material composition, moisture content, temperature, and maintenance. Race surface mechanical testing in a controlled laboratory setting would allow for objective evaluation of dynamic properties of surface and factors that affect surface behavior.

Objective

To develop a method for reconstruction of race surfaces in the laboratory and validate the method by comparison with racetrack measurements of dynamic surface properties.

Methods

Track-testing device (TTD) impact tests were conducted to simulate equine hoof impact on dirt and synthetic race surfaces; tests were performed both in situ (racetrack) and using laboratory reconstructions of harvested surface materials. Clegg Hammer in situ measurements were used to guide surface reconstruction in the laboratory. Dynamic surface properties were compared between in situ and laboratory settings. Relationships between racetrack TTD and Clegg Hammer measurements were analyzed using stepwise multiple linear regression.

Results

Most dynamic surface property setting differences (racetrack-laboratory) were small relative to surface material type differences (dirt-synthetic). Clegg Hammer measurements were more strongly correlated with TTD measurements on the synthetic surface than the dirt surface. On the dirt surface, Clegg Hammer decelerations were negatively correlated with TTD forces.

Conclusions

Laboratory reconstruction of racetrack surfaces guided by Clegg Hammer measurements yielded TTD impact measurements similar to in situ values. The negative correlation between TTD and Clegg Hammer measurements confirms the importance of instrument mass when drawing conclusions from testing results. Lighter impact devices may be less appropriate for assessing dynamic surface properties compared to testing equipment designed to simulate hoof impact (TTD).

Potential Relevance

Dynamic impact properties of race surfaces can be evaluated in a laboratory setting, allowing for further study of factors affecting surface behavior under controlled conditions.

The association of various speed indices to training responses in Thoroughbred flat racehorses measured with a global positioning and heart rate monitoring system

REASONS FOR PERFORMING STUDY

Fitness assessment can be challenging. The use of global positioning systems (GPS) with heart rate (HR) monitors has been promising; however, evaluation of speed parameters during training has not been reported.

OBJECTIVES

To evaluate speed indices during training in Thoroughbreds using a GPS-HR monitor.

METHODS

Thoroughbreds (n = 102) were assessed during training with data collected each work day (WD; sprinting). Speed indices evaluated included maximal velocity (V(max)), duration at V(max) (V(maxt)), acceleration rate (m/s(2)) from 800 m to V(max) (Acc800-V(max)), the distance (m) 6 (V(maxD6)) and 12 (V(maxD12)) s before (acceleration [a]) and after (deceleration [d]) V(max) and the deceleration rate from V(max) to the finish (V(maxDFd)). Blood for plasma lactate ([LA]) and creatine kinase ([CK]) measurements were taken before (T(0)), 5 mins (T(1)) and 6 h after exercise (T(2)). WD accumulation, jockey, gallop condition, horse gender, age, total distance covered (DistT), maximum HR (HR(max)), velocity at 200 beats/min (V(200)) and velocity at maximum HR (VHR(max)) for each WD were evaluated for associations with [LA], [CK], speed indices and racing performance. Data were analysed by repeated measures ANOVA with P < 0.05 significant.

RESULTS

No speed parameter clearly changed with training. Gallop condition affected V(max), V(maxt) and all distances covered with V(max) and distances increasing and V(maxt) decreasing as gallop surface became firmer. Jockey influenced V(max), V(maxD6a) and all decelerations, while DistT was inversely associated with Acc800-V(max), HR(max) and V(200) and positively associated with V(max), all accelerations and decelerations. [LA] at T(1) was positively associated with DistT and V(maxDFd).

CONCLUSIONS

Speed parameters did not change with training but were affected by jockey, gallop condition and exercise distance. This information may help to modify training to maximise fitness, minimise injury and choose distances best suited for individuals.

Time domain characteristics of hoof-ground interaction at the onset of stance phase

REASONS FOR PERFORMING STUDY

Little is known about the interaction of the hoof with the ground at the onset of stance phase although is it widely believed that high power collisions are involved in the aetiopathology of several conditions causing lameness.

OBJECTIVES

To answer 3 questions regarding the fundamental nature of hoof-ground collision: (1) is the collision process deterministic for ground surfaces that present a consistent mechanical interface (2) do collision forces act on the hoof in a small or large range of directions and (3) Is the hoof decelerated to near-zero velocity by the initial deceleration peak following ground contact?

METHODS

Hoof acceleration during the onset of stance phase was recorded using biaxial accelerometry for horses trotting on a tarmac surface and on a sand surface. Characteristics of the collision process were identified both from vector plots and time series representations of hoof acceleration, velocity and displacement.

RESULTS

The response of the hoof to collision with smooth tarmac was predominantly deterministic and consistent with the response of a spring-damper system following shock excitation. The response to collision with sand was predominantly random. The deceleration peak following ground contact did not decelerate the hoof to near-zero velocity on tarmac but appeared to on sand. On both surfaces, collision forces acted on the hoof in a wide range of directions.

CONCLUSIONS

The study suggests the presence of stiff, viscoelastic structures within the foot that may act as shock absorbers isolating the limb from large collision forces.

POTENTIAL RELEVANCE

The study indicates objectives for future in vivo and in vitro research into the shock absorbing mechanism within the equine foot; and the effects of shoe type and track surface properties on the collision forces experienced during locomotion. Studies of this nature should help to establish a link between musculoskeletal injury, hoof function and hoof-ground interaction if, indeed, one exists.

Veterinary-care events and costs over a 5-year follow-up period for warmblooded riding horses with or without previously recorded locomotor problems in Sweden

Our objective was to determine the amount, type and cost of veterinary care during a 5-year follow-up period, in Swedish warmblooded riding horses with and without locomotor problems as recorded in 1997. The study population comprised horses with complete insurance both for veterinary care and life during 1997. The horses were followed from the beginning of January 1998 to the end of December 2002. The exposed cohort was composed of 1558 horses that had experienced >or=1 veterinary-care event because of locomotor problems in 1997 (LP-cohort). The exposure-negative (LN) cohort was composed of 16,513 horses that had no recorded locomotor problem during 1997. For the outcome of locomotor problems during the follow-up period, stratified incidence proportions and a repeated-measures multivariable-logistic regression model in general produced the same conclusions. An interaction between year and cohort showed larger odds ratios (ORs) in the first year of follow-up compared to later (OR 4.8 and 1.2 in the LP- and LN-cohort, respectively), but a smaller difference during the subsequent years (in the 5th year OR 1.8 and 1.0, respectively). Horses with life-insurance values of >30,000 SEK in the LP- and LN-cohorts had ORs of 4.7 (99% CI 3.9, 5.6) and 2.6 (99% CI 2.3, 2.9), respectively. For life-insurance values of <or=10,000 SEK the respective ORs were 3.4 (99% CI 2.6, 4.4) and 1 (baseline). The yearly costs for reimbursed veterinary care for locomotor problems during the 5-year follow-up, per horse at risk, varied from 880 to 1320 SEK (approximately US$ 100-150) in the LP-cohort and between 410 and 580 SEK (US$ 46-66) in the LN-cohort. In conclusion, the horses with previous locomotor problems continued to have considerably more veterinary-care events and higher costs for locomotor problems during the follow-up period.

A novel wireless data acquisition system for the measurement of hoof accelerations in the exercising horse

REASONS FOR PERFORMING STUDY

A device is needed to safely and wirelessly evaluate accelerations experienced by the horse hoof under a variety of surface conditions with the horse exercising at training or racing speeds.

OBJECTIVES

To develop a miniaturised wireless data acquisition system (WDAS) which reliably records hoof accelerations and the times over which they occur in a minimally invasive manner in the exercising Thoroughbred.

METHODS

The following criteria were set for device development: production of a lightweight and minimally invasive system, which provides an adequate acceleration range, appropriate frequency response to capture high speed events, and compatibility with a low power wireless telemetry system. Following device development, the WDAS was calibrated, and tested in 6 Thoroughbred horses over a variety of surfaces.

RESULTS

Collection of acceleration in seven trials using 6 horses over a variety of surfaces resulted in repeatable acceleration data with respect to the overall characteristic shape of the impact profile. Impact accelerations varied with surface, ranging 34.8-191.7 g. Accelerations on take off were in a similar range, although higher in some trials. Peak impact accelerations tended to larger over the grass paddock surface, than either the indoor arena or the dirt track. During dirt track trials, accelerations on take-off were often comparably larger than those observed on impact within the same footfall.

CONCLUSIONS

This study reports the development of a wireless system that successfully measures hoof acceleration in a minimally invasive manner over a variety of surface and exercise conditions.

POTENTIAL RELEVANCE

The WDAS will be used in further studies to evaluate various components of the horse-racetrack interface, in an attempt to identify risk factors for musculoskeletal injury in the Thoroughbred racehorse.

The horse-racetrack interface: a preliminary study on the effect of shoeing on impact trauma using a novel wireless data acquisition system

REASONS FOR PERFORMING STUDY

There is a need to determine accelerations acting on the equine hoof under field conditions in order to better assess the risks for orthopaedic health associated with shoeing practices and/or surface conditions.

OBJECTIVES

To measure the acceleration profiles generated in Thoroughbred racehorses exercising at high speeds over dirt racetracks and specifically to evaluate the effect of a toe grab shoe compared to a flat racing plate, using a newly developed wireless data acquisition system (WDAS).

METHODS

Four Thoroughbred racehorses in training and racing were used. Based on previous trials, each horse served as its own control for speed trials, with shoe type as variable. Horses were evaluated at speeds ranging from 12.0-17.3 m/sec. Impact accelerations, acceleration on break over and take-off, and temporal stride parameters were calculated. Impact injury scores were also determined, using peak accelerations and the time over which they occurred.

RESULTS

Recorded accelerations for the resultant vector (all horses all speeds) calculated from triaxial accelerometers ranged 96.3-251.1 g, depending on the phase of the impact event. An association was observed between shoe type and change in acceleration in individual horses, with 2 horses having increased g on initial impact with toe grab shoes in place. In the final impact phase, one horse had an increase of 110 g while wearing toe grab shoes. Increased accelerations were also observed on break over in 2 horses while wearing toe grab shoes.

CONCLUSIONS

Shoe type may change impact accelerations significantly in an individual horse and could represent increased risk for injury. Further work is needed to determine if trends exist across a population.

POTENTIAL RELEVANCE

The WDAS could be used for performance evaluation in individual horses to evaluate any component of the horse-performance surface interface, with the goal of minimising risk and optimising performance.

Determination of coefficient of friction between the equine foot and different ground surfaces: an in vitro study

Slippery surfaces are a continuous concern in equine veterinary practice during both treatment and orthopaedic work-ups, especially when horses have to trot on circles. Sliding of the equine foot on the ground with the potential of injury is prevented if the horizontally acting accelerating or decelerating forces on the foot do not exceed maximal friction. Friction can be calculated and therefore anticipated if the coefficient of friction (μ) between the foot of the horse and the particular ground surface is known. Friction between shod and unshod cadaver equine hooves and different ground surfaces (concrete, tarmac and rubber) was determined by pulling the hooves horizontally in a uniform motion. Horizontal forces (Fh) were measured on a force plate and with a portable digital electronic force meter. The coefficient of friction (μ) was calculated as the quotient between Fh and the gravity force (N) of the object, hence: μ = Fh /N. This study has shown that the coefficient of friction between equine hooves and a specific ground surface can be determined using a portable digital force meter or a force plate. Friction significantly depended not only on the type of surface but also on shoeing of the equine foot. Bare feet showed more friction with the hard surfaces (bricks and tarmac), the shod feet showing more friction with the rubber surfaces. Coefficients of friction could be used to estimate the possibility of injuries occurring in the equine industry during exercise and/or lameness or pre-purchase examinations.

Ground reaction force and hoof deceleration patterns on two different surfaces at the trot

The objective of the present study was to compare the hoof deceleration and ground reaction forces following impact on two different surfaces. Seven unshod Standardbreds were trotted by hand at 3.0–5.7 m s− 1 over a force plate covered by either of the two surfaces, sandpaper or a 1 cm layer of sand. Impact deceleration data were recorded from one triaxial accelerometer mounted on the fore- and hind hooves, respectively. Ground reaction force data were obtained synchronously from a force plate, sampled at 4.8 kHz. The differences between the two surfaces were studied by analysing representative deceleration and force variables for individual horses. The maximum horizontal peak deceleration and the loading rates of the vertical and the horizontal forces were significantly higher on sandpaper compared with the sand surface (P < 0.001). In addition, the initial vertical deceleration was significantly higher on sandpaper in the forelimb (P < 0.001). In conclusion, it was shown that the different qualities of the ground surface result in differences in the hoof-braking pattern, which may be of great importance for the strength of the distal horse limb also at slow speeds.