D. Robin

Effects of a synthetic all-weather waxed track versus a crushed sand track on 3D acceleration of the front hoof in three horses trotting at high speed.

REASONS FOR PERFORMING STUDY Inadequate track surfaces are believed to be a risk factor in the occurrence of musculoskeletal injuries, but quantification of the shocks and vibrations provoked by hoof impact on different ground surfaces (including new synthetic tracks) has been insufficiently documented in trotters under high-speed training conditions. OBJECTIVES To test the reliability and sensitivity of an accelerometric device to discriminate between the biomechanical effects of 2 different tracks at high speed. METHODS Three French Trotters were used and their right front hooves were equipped with one triaxial accelerometer. Two different track surfaces (crushed sand track: S and all-weather waxed track: W) were tested when horses were trotting in a straight line. For each session of measurements, trials were repeated 3 times in a Latin square design. The speed of the runs was set at 10 m/s, controlled by the driver and recorded synchronously. Sample rate was set at 6 kHz. Acceleration of the hoof (resultant vector and 3D components), power spectral density at impact and variability (between strides, trials, sessions and horses) were analysed. Statistical differences were tested using a GLM procedure (SAS). Least square mean differences were used for comparisons between tracks (P < 0.05). RESULTS Results showed that the deceleration of the hoof (magnitude of the resultant vector) was statistically different between the 2 tracks with an attenuation of the shock of about 50% on the all-weather waxed track. Magnitude of the power spectral density was reduced at higher frequencies on W. CONCLUSIONS AND CLINICAL RELEVANCE These preliminary results demonstrate the sensitivity of the tool to discriminate between the different behaviours of the hoof on the different track surfaces at high speed. Deceleration and vibration of the hoof at impact were reduced on W compared to S, suggesting a better shock-absorbing quality of this track.

Design and validation of a dynamometric horseshoe for the measurement of three-dimensional ground reaction force on a moving horse

Properties of ground surfaces condition locomotion, and quality of track surfaces is believed to be involved in the pathogenesis of many musculoskeletal injuries in the horse. Measuring ground reaction forces (GRF) is an interesting approach to assess those interactions. Forceplates are the most commonly used but they are not well suited to compare different ground surfaces at fast gaits. Embarked equipment, fixed under the horses hoof, would allow force measurement on any track. The objective of this work was (1) to design a device which enables the measurement of 3-D GRF on any ground, at any gait, for a given subject, (2) to determine its accuracy, and (3) to evaluate its performance and usefulness under physiological conditions. The resulting dynamometric horseshoe was composed of 4 piezoelectric sensors sandwiched between 2 aluminium plates designed at the shape of an equine shoe. The measurements, evaluated after a quasi-static calibration, revealed that the root mean square error was 1.3% in the normal direction, and 3.1% in the transversal direction. In vivo tests at the walk and trot in straight line and at the trot on circles, were conducted on 3 different ground surfaces. The results demonstrate that this dynamometric horseshoe is well suited to study the effects of different ground surfaces on GRF in the moving horse.

Biomechanical analysis of hoof landing and stride parameters in harness trotter horses running on different tracks of a sand beach (from wet to dry) and on an asphalt road

REASONS FOR PERFORMING STUDY Sandy beaches are often considered good training surfaces for trotter horses. However, their biomechanical effects on locomotion are insufficiently documented. Events at hoof impact have mostly been studied under laboratory conditions with accelerometers, but there is lack of data (acceleration, force, movement) on events occurring under every day practical conditions in the field. OBJECTIVES To investigate hoof landing and stride parameters on different tracks (from wet to dry) of a sand beach and on an asphalt road. METHODS The right front hoof of 4 trotter horses was equipped with a triaxial accelerometer and a dynamometric horseshoe. Acceleration and force recordings (10 kHz) were synchronised with a high speed movie (600 Hz). Horses were driven on a sand beach where 3 tracks of decreasing water content had been delimited (from the sea to the shore): firm wet sand (FWS), deep wet sand (DWS) and deep dry sand (DDS). Firm wet sand and DWS were compared at 25 km/h and DDS compared to an asphalt road at 15 km/h. Recordings (10 strides) were randomly repeated 3 times. Statistical differences were tested using a GLM procedure (P < 0.05). RESULTS Main significant results were 1) a decrease in the amplitude of the vertical deceleration (and force) of the hoof during impact on a softer surface (about 59% between DWS and FWS and 95% between DDS and asphalt), 2) a decrease in the longitudinal braking deceleration (and force) on softer grounds (50% for DWS vs. FWS and 55% for DDS vs. asphalt), 3) a decrease in the stride length and an increase in the stride frequency on a softer surface. CONCLUSIONS AND CLINICAL RELEVANCE Drier sand surfaces reduce shock and impact forces during landing. For daily training, it should, however, be realised that improved damping characteristics are associated with a shorter stride length and a higher stride frequency.

Use of a 3D dynamometric horseshoe to assess the effects of an all-weather waxed track and a crushed sand track at high speed trot: Preliminary study

REASONS FOR PERFORMING STUDY Track surface quality is considered a risk factor of musculoskeletal injuries. Ground reaction force (GRF) measurement is a relevant approach to study the interaction between the hoof and the ground. Force plates are not adapted to compare different surfaces at high speed. A 3D dynamometric horseshoe (DHS), using 4 triaxial piezoelectric sensors, has been developed and validated. OBJECTIVES To use the DHS to compare the effects of 2 track surfaces, an all-weather waxed track and a crushed sand track, on the GRF in trotter horses under training conditions. METHODS The right forelimb of 3 French Trotters was equipped with the DHS. Two tracks were tested in a straight line: a crushed sand track (S) and an all-weather waxed track (W). For each session, trials were repeated 3 times in a Latin square design. The speed of the runs was set at 10 m/s and recorded synchronously. For each trial, data acquisition was performed at 600 Hz and 10 consecutive strides were analysed. Statistical differences were tested using a general linear model procedure. RESULTS The amplitude of the maximal longitudinal braking force (Fx) was significantly lower on W compared to S. This event happened about 6% later in the stance phase on W. The magnitude of the GRF at impact decreased on W. The average speed and the mean stance phase duration were not statistically different on both surfaces. The stride length was about 6 cm longer on S. CONCLUSION AND POTENTIAL RELEVANCE This study demonstrates the ability and sensitivity of the DHS to discriminate track surfaces by measuring the GRF at high speed. These preliminary results show that the loading rate, the amplitude of horizontal braking and shock at impact are attenuated on W, which suggests a reduction of stresses in the distal limb.

Ground reaction force and kinematic analysis of limb loading on two different beach sand tracks in harness trotters.

REASONS FOR PERFORMING STUDY Although beach training is commonly used in horses, limb loading on beach sand has never been investigated. A dynamometric horseshoe (DHS) is well adapted for this purpose. OBJECTIVES To compare ground reaction force (GRF) and fetlock kinematics measured in harness trotters on 2 tracks of beach sand with different water content. METHODS Two linear sand tracks were compared: firm wet sand (FWS, 19% moisture) vs. deep wet sand (DWS, 13.5% moisture). Four French trotters (550 ± 22 kg) were used. Their right forelimb was equipped with a DHS and skin markers. Each track was tested 3 times at 7 m/s. Each trial was filmed by a high-speed camera (600 Hz); DHS and speed data acquisition was performed at 10 kHz on 10 consecutive strides. All recordings were synchronised. The components Fx (parallel to the hoof solar surface) and Fz (perpendicular) of the GRF were considered. For 3 horses the fetlock angle and forelimb axis-track angle at landing were measured. Statistical differences were tested using the GLM procedure (SAS; P < 0.05). RESULTS Stance duration was increased on DWS compared to FWS. Fzmax and Fxmax (oriented, respectively, downwards and forwards relatively to the solar surface) and the corresponding loading rates, were decreased on DWS and these force peaks occurred later. Fxmin (backwards) was not significantly different between both surfaces; the propulsive phase (Fx negative) was longer and the corresponding impulse higher, on DWS compared to FWS. The forelimb was more oblique to the track at landing and maximal fetlock extension was less and delayed on DWS. CONCLUSIONS This study confirms that trotting on deep sand overall reduces maximal GRF and induces a more progressive limb loading. However, it increases the propulsive effort and likely superficial digital flexor tendon tension at the end of stance, which should be taken into account in beach training.

Use of a 3D dynamometric horseshoe for the measurement of grip parameters in a horse cantering on right and left circles on two surfaces

The notion of grip, or traction, between a sport surface and the athlete’s shoes is a critical parameter as it conditions performance but can also be a factor of injury. In human sport, grip has been investigated in order to improve the design of shoes and surfaces through characteristics such as dynamic traction coefficient and dynamic vertical torque. The same kind of improvement could be obtained for equine competition surfaces on which the horses have to perform sharp turns. In this context, biomechanical parameters related to grip must be defined and measured under sport conditions, which require the measurement of the triaxial hoof reaction force (HRF). The purpose of this study was to comparatively assess the grip of two surfaces, one designed for competition and the other for instruction, while measuring the HRF in a horse cantering in circles.

External loads on the leading and trailing forelimbs of a jumping horse at landing measured with a dynamometric horseshoe

with a dynamometric horseshoe N. Crevier-Denoix*, M. Camus, S. Falala, B. Ravary-Plumioen, L. Douilly-Holden, D. Robin, J.-M. Denoix, H. Chateau and P. Pourcelot Université Paris Est, Ecole Nationale Vétérinaire d’Alfort, USC 957 BPLC, F-94700 Maisons-Alfort, France; INRA, USC 957 BPLC, F-94700 Maisons-Alfort, France; Université Paris Est, Ecole Nationale Vétérinaire d’Alfort, CIRALE, F-14430 Goustranville, France

Biomechanical analysis of hoof landing in horses trotting at high speed and the effects of ground surfaces

Excessive and repetitive loadings are thought to induce injury to the distal limb (Radin 1999). Therefore, the phase of rapid loading following initial contact of the hoof with the surface is thought to be important for the orthopaedic health of the horse (Johnston and Back 2006). Shock and vibration during hoof impact on different ground surfaces have already been measured. The biomechanical analysis of hoof landing combining kinematics of the hoof, 3D deceleration, 3D forces and CoP has not been investigated yet during high-speed exercise in the field condition because of the technical issues of such challenging conditions. As the events during this initial phase of the stance are believed to be modified by track surfaces, these have been incriminated in the induction of injurious loading and movement. Hypothesis can be made that the properties of different ground surfaces can alter the kinetic and kinematic patterns of hoof landing. The aim of the present study is to describe the mechanism of hoof landing in the trotting horse at high speed and to evaluate the effects of different ground surfaces on this phenomenon.Recent numerical studies of abdominal aortic aneurysm (AAA) suggest that intraluminal thrombus (ILT) may reduce the stress loading on the aneurysmal wall. Detailed fluid structure interaction (FSI) in the presence and absence of ILT may help predict AAA rupture risk better. Two patients, with varied AAA geometries and ILT structures, were studied and compared in detail. The patient specific 3D geometries were reconstructed from CT scans, and uncoupled FSI approach was applied. Complex flow trajectories within the AAA lumen indicated a viable mechanism for the formation and growth of the ILT. The resulting magnitude and location of the peak wall stresses was dependent on the shape of the AAA, and the ILT appeared to reduce wall stresses for both patients. Accordingly, the inclusion of ILT in stress analysis of AAA is of importance and would likely increase the accuracy of predicting AAA risk of rupture.

Comparison between accelerometer and kinematic techniques for the evaluation of hoof slip distance: a preliminary study

Sliding of a horse’s feet on the ground conditions mechanical solicitations of the equine limbs. Although it could be theoretically considered as a possible factor in injuries, hoof sliding could also be, when moderate, a factor of performance, especially in trotters. Besides, as sliding of the foot allows energy dissipation, the rate of application of the ground reaction force is slower, thus placing the tissues of the limb under less stress during landing (Nigg and Segesser 1988). To date, slip measurement has been exclusively documented at low paces predominantly using kinematic techniques (Pardoe et al. 2001; Di Domenico et al. 2007). However, the latter are not convenient to use when the horse moves at high speed in outdoor conditions, because the cameras have to follow the horse. Another conceivable method is the double integration of the hoof deceleration at the beginning of the stance (Burn 2006). Hence, the main purpose of this preliminary study was to compare, under laboratory conditions, the kinematic and accelerometric techniques of measuring slip distance.

Suitability of a dynamometric horseshoe for the recording of the ground reaction forces on ridden horses

Limb injuries are common in race and sport horses and they often induce a premature end to a horse’s sport career. It is generally accepted that limb loading during the stance phase is most potentially detrimental for the orthopaedic health of the performing horse. Force plates are commonly used to measure the ground reaction force (GRF), but they are inappropriate for recordings during training conditions. Recently, a new model of dynamometric horseshoe (DHS) has been designed (Chateau et al. 2009) and then used to study the effects of different ground surfaces on the GRF to harness trotters (Robin et al. 2009). It has thus become evident that the DHS can be used in the field, on training or racing surfaces, and at high speed. However, the data acquisition system initially positioned on a sulky was too large to be used in a ridden horse and, therefore, it needed to be adapted. The main goal of this study was to test the suitability of the DHS with a new miniaturised data acquisition system for the measurement of the GRF in several exercises (such as cantering on a circle and fence jumping) commonly performed with ridden horses.