Comparison of vertical force redistribution in the pads of dogs with elbow osteoarthritis and healthy dogs.

Kinetic analyses are becoming increasingly important for biomechanical research in veterinary medicine and as a diagnostic tool for orthopaedic examinations in dogs. Such analysis enables accurate evaluation of the vertical force distribution (VFD) in canine paw pads. The aim of this study was to assess peak vertical force (PFz) as a percent of total force (%TF), vertical impulse (IFz, %TF) and time of occurrence of PFz (TPFz) as a percent of the stance phase (%SP) in the pads of all four limbs in 23 dogs with osteoarthritis in the elbow joint and 22 healthy dogs. Dogs walked over a pressure plate, and the pads were divided into four quadrants for VFD analysis. For statistical analysis, a general linear model was used to examine the difference in VFD between both groups, between fore- and hindlimbs, between body sides, and between medial/lateral and cranial/caudal quadrants. Lame dogs had lower PFz in the lame forelimb than in other limbs and transferred their weight to the caudal quadrants of the contralateral forelimb and the caudomedial quadrant of both hindlimbs. IFz was also lower in the affected forelimb and was compensated through higher loading of the caudal quadrants of the contralateral forelimb, the caudomedial quadrants of both hindlimbs and the caudolateral quadrant of the contralateral hindlimb. TPFz (%SP) occurred later in both forelimbs of the lame dogs than in those of healthy dogs. The analysis of force distribution over the paw quadrants can be used for further biomechanical studies of dogs with orthopaedic and neurological diseases.

Vertical force distribution in the paws of sound Labrador retrievers during walking.

In contrast to gait analysis in humans, where pedobarography is an integral part of biomechanical studies, veterinary researchers have rarely investigated vertical force distribution (VFD) in the paws of dogs. The aim of this study was to investigate the VFD of peak of vertical force (PFz), vertical impulse (IFz) and time of occurrence of PFz during stance phase (TPFz) in 20 sound, adult Labrador retrievers walking normally on a pressure plate. A technique was used that divided the canine paw prints into quadrants. A general linear model was introduced to investigate the effects of forelimbs/hindlimbs, body side, and medial/lateral and cranial/caudal quadrants on VFD as they related to the total force (sum of all PFz/IFz values). For PFz and IFz, there were significantly greater effects on VFD in the lateral quadrants compared to the medial quadrants, respectively (6.49 ± 2.56% vs. 6.01 ± 2.60% and 6.62 ± 3.06% vs. 5.88 ± 3.21%; P < 0.001), in the forelimbs compared to the hindlimbs (8.02 ± 2.13% vs. 4.48 ± 1.61% and 8.02 ± 2.83% vs. 4.48 ± 2.36%; P < 0.001), and in the cranial quadrants compared to the caudal quadrants (7.87 ± 2.09% vs. 4.63 ± 1.93% and 8.57 ± 2.17% vs. 3.88 ± 1.98%; P < 0.001). The cranial/caudal ratio was higher in the hindlimbs than in the forelimbs (PFz: 2.10 ± 0.45 vs. 1.65 ± 0.32; P = 0.001; and IFz: 3.35 ± 0.80 vs. 2.04 ± 0.46; P < 0.001). The TPFz was reached earlier in the hindlimbs than in the forelimbs (46.86 ± 19.16% vs. 54.08 ± 19.62%; P < 0.001) and in the caudal quadrant than in the cranial quadrant (32.57 ± 5.77% vs. 68.37 ± 10.01%; P < 0.001). These data from sound Labrador retrievers could be used as a basis for future research investigating orthopedically- and/or neurologically-impaired animals.

Pressure distribution under three different types of harnesses used for guide dogs.

The aim of this study was to evaluate the pressure distribution under three different types of harnesses used for guide dogs (designated H1, H2 and H3). The dogs (n = 8) led a trainer through a course including a range of exercises (straight line, curve left, curve right, upstairs and downstairs). All dogs were clinically sound and showed no sign of lameness. The pressures beneath the harnesses were determined by sensor strips and related to the gait. In all harnesses, the highest pressures were found in the right sternal region (H1 2.02 ± 0.6N/cm(2); H2 1.76 ± 0.4N/cm(2); H3 1.14 ± 0.5 N/cm(2)). In all other regions, the pressures were in the range of 0-1.32 N/cm(2). The right and left sternal regions were almost constantly loaded. Contrary to previous assumptions, the back regions had minimal loading. This investigation demonstrated that there were significant differences among the harnesses.

[Monitoring of dairy cow claw health status in 15 herds using the computerised documentation program Claw Manager and digital parameters]. / Langzeitkontrolle der Klauengesundheit von Milchkühen in 15 Herden mithilfe des Klauenmanagers und digitaler Kennzahlen.

OBJECTIVE: Monitoring of claw health over a defined period using the digital documentation and analysis program Claw Manager. MATERIAL AND METHODS: Data from 679 cows were documented with the Claw Manager during routine functional claw trimming on 15 dairy farms that were visited two or three times. The data of these 33 visits were analysed for the following parameters: prevalence of claw lesions, of their severity scores and of lameness as well as the Cow Claw Score (CCS), the Farm Claw Score (FCS) and the Farm Zone Score (FZS). Their chronological progression was shown using boxplot graphs. RESULTS: Mean prevalence of all lame free cows was 71.9% at visit 1 (max. 95.0%, min. 21.1%) and 72.9% at visit 2 (max. 100.0%, min. 12.6%). The mean prevalence of claw lesions in all 15 herds was 61.8% for heel horn erosion (HHE), followed by white line lesions (WLL, 37.2%), sole haemorrhages (SH, 27.5%), acute and chronic stages of digital dermatitis (DD, 19.7%) and chronic laminitic claws (10.9%). In individual herds HHE (n = 15), WLL (n = 11), SH (n = 10), acute DD (n = 4) and chronic laminitic claws (n = 3) were consistently among the three most frequently observed lesions. A statistically significant improvement was found for the severity scores of the claw lesions of all cows from visit 1 to visit 2. The CCS ranged from 0 (CCS min) to 276 (CCS max), the FCS ranged from 6 to 72. The length of the upper quartiles and the length of the upper whiskers in the boxplot graphs of the CCS values of the herds at the various visits varied widely. The CCS of the cows of ten herds improved significantly from visit 1 to visit 2. Locomotion scores and CCS were significantly correlated on 30 of 33 visits. CONCLUSION: The parameters FCS (median of all CCS values of a herd), length of the upper quartiles, length of the upper whiskers in the boxplot graphs FZS max, the prevalence of lameness and of claw lesions, and their severity scores proved to be very informative for a detailed comparison of claw data of herds over subsequent visits.

How securely is the testicular artery occluded in the spermatic cord by using a ligature?

REASONS FOR PERFORMING STUDY: There are no studies on the ideal ligature technique for the spermatic cord. OBJECTIVES: To compare the maximal resistance pressure in the testicular artery and the maximal tensile forces to produce failure of 2 different ligature techniques used for ligation of the equine spermatic cord. METHODS: The capabilities of 2 types of ligatures, single knot loop and double knot loop, were assessed using a pressure-resistance test in testicular arteries and with an in vitro mechanical evaluation of the tensile strength by single cycle-to-failure testing. RESULTS: In the pressure-resistance test, the mean ± s.d. peak force at failure of the single knot loop was 354.4 ± 91.7 mmHg and for the double knot loop 303.2 ± 62.0 mmHg. There was no significant difference between the maximal load to failure of the single knot loop and double knot loop technique. The pressure needed for rupture was significantly higher (P = 0.001) than for leakage. The maximal tensile force at failure of the single knot loop was significantly higher than the double knot loop (P = 0.028). There was no significant difference in load elongation properties to failure between the single knot loop and double knot loop. CONCLUSIONS: Although no significant differences were obtained in the pressure-resistance test, the single knot loop sustained significantly greater load to failure than the double knot loop in single cycle-to-failure testing. Based on these findings, it would appear that the performance of the single knot loop should be superior to the double knot loop. POTENTIAL RELEVANCE: Both ligature techniques are able to withstand the normal physiological intravascular pressure. The single knot loop has the greater breaking strength of the 2 ligatures tested and is less time consuming to perform and may therefore have advantages during equine castration.

The jump shot - a biomechanical analysis focused on lateral ankle ligaments.

Handball is one of the top four athletic games with highest injury risks. The jump shot is the most accomplished goal shot technique and the lower extremities are mostly injured. As a basis for ankle sprain simulation, the aim of this study was to extend the ankle region of an existing musculoskeletal full-body model through incorporation of three prominent lateral ankle ligaments: ligamentum fibulotalare anterius (LFTA), ligamentum fibulotalare posterius (LFTP), ligamentum fibulocalcaneare (LFC). The specific objective was to calculate and visualise ligament force scenarios during the jumping and landing phases of controlled jump shots. Recorded kinematic data of performed jump shots and the corresponding ground reaction forces were used to perform inverse dynamics. The calculated peak force of the LFTA (107 N) was found at maximum plantarflexion and of the LFTP (150 N) at maximum dorsiflexion. The peak force of the LFC (190 N) was observed at maximum dorsiflexion combined with maximum eversion. Within the performed jump shots, the LFTA showed a peak force (59 N to 69 N) during maximum plantarflexion in the final moment of the lift off. During landing, the force developed by the LFTA reached its peak value (61 N to 70 N) at the first contact with the floor. After that, the LFTP developed a peak force (70 N to 118 N). This model allows the calculation of forces in lateral ankle ligaments. The information obtained in this study can serve as a basis for future research on ankle sprain and ankle sprain simulation.

A preliminary model study of the equine back including activity of longissimus dorsi muscle.

REASONS FOR PERFORMING STUDY: Identifying the underlying problem of equine back pain and diseases of the spine are significant problems in veterinary orthopaedics. A study to validate a preliminary biomechanical model of the equine back based on CT images including longissimus dorsi (LD) muscle is therefore important. OBJECTIVES: Validation of the back model by comparing the shortening of LD muscles in the model with integrated EMG (IEMG) at stance during induced lateral flexion of the spine. METHODS: Longissimus dorsi muscle activity at stance has been used for validation. EMG electrodes were placed laterally at the level of T12, T16 and L3. Reflective markers have been attached on top of the spinous processes T5, T12, T16, L1 and the sacral bone (OS1, OS2) for motion tracking analysis. A virtual model of the equine's back (T1-S5) was built with inclusion of a simplified LD muscle by 2 separate contours left and right of the spine, starting at tuber coxae laterally and attaching to the spinous process T5 medially. Shortening of LD during induced lateral flexion caused by the kinematic data (input) was compared to the 3 EMG signals (T12, T16 and L3) on the active side via correlation. RESULTS: Pearson correlation coefficient between IEMG and shortening length of LD in the model was (mean ± s.d.) 0.95 ± 0.07 for the left side and 0.91 ± 0.07 for the right side of LD. CONCLUSIONS: Activity of the LD muscles is mainly responsible for stabilisation of the vertebral column with isometric muscle contraction against dynamic forces in walk and trot. This validation requires muscle shortening in the back, like induced lateral flexion at stance. The length of the shortening muscle model and the IEMG show a linear relationship. These findings will help to model the LD for forward simulations, e.g. from force to motion.

Influence of shoes with different weights on the motion of the limbs in Icelandic horses during toelt at different speeds.

REASON FOR PERFORMING STUDY: Weight boots are commonly used for Icelandic horses to increase the height of the flight arc of the forelimbs in toelt. OBJECTIVE: To show the influence of weights and toelting speed on the height of the swing phase. MATERIALS AND METHODS: Eight Icelandic horses (mean ± s.d. 12 ± 3 years old, 369 ± 46 kg) were used. Reflecting makers were placed on the dorsal side of each hoof. The motion was collected with a kinematic system (10 cameras, 120 Hz sample rate, 1.3 Mpixels resolution). The horses were ridden in toelt by 2 experienced riders on a treadmill at 2 different speeds (2.96 m/s ± 0.30 and 4.10 m/s ± 0.32). At each speed the horses were measured wearing no boots, light boots (170 g) and heavy boots (280 g) on both fore hooves. The measurement sequence was varied between horses. A Kolmogorov-Smirnov test was carried out to test for normal distribution of data and ANOVA for repeated measurements were used to compare differences (P < 0.05). RESULTS: The weight as well as the speed of toelt had a significant influence on the height of the flight arc. At the lower speed, the mean ± s.d. height was 163 ± 55 mm, whereas at the higher speed the mean height was 228 ± 60 mm. The heavy weights increased the mean height at the lower speed from 152 ± 38 to 169 ± 48 mm and at the higher speed from 214 ± 60 to 245 ± 60 mm. CONCLUSIONS: This investigation shows that Icelandic horses can be expected to show a better toelt in competitions with weights, and ridden at a higher speed. For muscle adaptation to occur, weights should therefore be used during competitions and training.

Electromyography activity of the equine splenius muscle and neck kinematics during walk and trot on the treadmill.

REASONS FOR PERFORMING STUDY: Skeletal muscle activity can be concentric or eccentric, anisometric or isometric and correlation of the equine splenius muscle activity with the movement of its effector joints at walk and trot has not yet been fully characterised. OBJECTIVE: Investigating activity of the splenius muscle together with kinematics of head and cranial neck at walk and trot. MATERIALS AND METHODS: Kinematics and surface electromyography were measured in 6 horses (8-20-years-old, 450-700 kg) without signs of neck pain. Markers were placed on left and right crista facialis, and on left and right cervical vertebrae 1 and 3. Head and neck angle was calculated in sagittal and horizontal planes. Electrodes were placed over both splenius muscles at the level of C2. Left and right muscle activity was compared using Student t test for paired samples and correlations calculated using Pearson correlation coefficient. Significance was set at P < 0.05. RESULTS: In all horses, maximum surface electromyography (sEMG) values at the trot were higher than at the walk. The intraindividual differences between maximum and minimum values of the EMG ranged from 45-127 mV in walk and from 154-524 mV in trot. Flexion-extension C1 angle changed by 43° in walk and 27° in trot. For each motion cycle, 2 EMG maxima were found in both gaits, occurring just prior to maximum extension of the C1 angle. Lateral bending at C1 angle changed by 16° in walk and 17° in trot and EMG reached maximum values bilaterally during maximum lateral bending at walk. CONCLUSIONS: The splenius muscle reaches maximum activity at the beginning of the forelimb stance phases in trot, indicating functional stabilisation against flexion of the head and neck. Unilateral activity of the splenius muscle representing stabilisation against lateral movement was not found.

A preliminary modelling study on the equine cervical spine with inverse kinematics at walk.

REASON FOR PERFORMING STUDY: The motion of the atlanto-occipital, cervical vertebral and cervicothoracic joints play an important role in equestrian sports and they are also common sites for lesions limiting performance in horses. OBJECTIVES: To calculate inverse kinematics based on cervical vertebral motion and to develop a model close to the measured neck movements. MATERIALS AND METHODS: Measurements were recorded in 6 horses without neck pain. Reflective markers were placed on both cristae facialis, both sides of cervical vertebra 1, 3 and 6 on the withers and hooves. The neck model was reconstructed from CT scans of the osseus structures and was developed in SIMM (Software for Interactive Musculoskeletal Modelling). Inverse kinematics calculation was done in OpenSim. Three degrees of freedom: Flexion-extension (FE), axial rotation (AR) and lateral bending (LB) were considered. The simulated motion was generated from the recorded motion of the skin markers. The differences in angular range of motion (ROM) of the joints were analysed using paired sample t tests. RESULTS: From the model, the smallest FE ROM was in the C5-C6 joint (2° ± 1°) and the largest was in the C3-C4 joint (11° ± 5°). The smallest AR ROM was in the C5-C6 joint (2° ± 1°) and largest AR ROM was in the atlantoaxial joint (7° ± 2°). The smallest LB ROM was in the C5-C6 joint (2° ± 1°) and the largest LB ROM was in the cervicothoracic joint (18° ± 5°). There were significant differences between the ROM of joints in 51 of 168 comparisons (P < 0.05). CONCLUSIONS: The result of the motion of each joint gives an insight into the biomechanics of the equine neck. The small FE ROM at C5-C6 illustrates the pathogenetical relevance of the model for the development of osteoarthritis. The calculated data also provides a source for inverse dynamics.

Activity of the equine rectus abdominis and oblique external abdominal muscles measured by surface EMG during walk and trot on the treadmill.

REASON FOR PERFORMING STUDY: The rectus abdominis (RA) and oblique external abdominal (OEA) muscles are both part of the construction of the equine trunk and thought to be essential for the function of the spine during locomotion. Although RA activity at trot has previously been investigated, the relationship between OEA and RA at walk and trot has not yet been described. OBJECTIVES: To document abdominal muscle activities during walk and trot, and test the hypothesis that muscle activity at walk would be smaller than at trot. MATERIALS AND METHODS: Six horses (8-20 years old, 450-700 kg) were used for surface electromyography (EMG) measurements, with EMG electrodes placed caudal to the sternum (RA) and at the level of the 16th rib (OEA). On all hooves, the withers and the sacrum reflective markers were placed to determine motion cycles. Normal distribution of data was tested using a Kolmogorov-Smirnov test and Student's t test was used to compare left-right and walk-trot differences (P < 0.05). RESULTS: Minimum, maximum and mean EMG values recorded at walk were significantly higher at trot than at walk in all horses for OEA and in 5/6 horses for RA. At walk, EMG activity ranged from 8-44 mV (RA) and 7-54 mV (OEA). At trot, EMG activity ranged from 18-150 mV (RA) and 27-239 mV (OEA). There were statistically significant differences between maximum activities of left and right OEA and RA muscles at walk in all horses, and in 4/6 horses at trot. CONCLUSIONS: Muscle activities of OEA and RA are smaller at walk than at trot. At walk, the OEA/RA ratio is lower than at trot. There are more significant correlations between muscle activities of both RA and OEA and limb movements at walk than at the trot.

The effects of different saddle pads on forces and pressure distribution beneath a fitting saddle.

REASON FOR PERFORMING STUDY: Saddle pads are widely used in riding sports but their influence on saddle pressures is poorly understood. OBJECTIVE: To evaluate the forces acting on the horse's back, and the eventual pressure distribution by using different saddle pads underneath a fitting saddle. METHODS: Sixteen sound horses of different breeds and ages were ridden on a treadmill at walk and sitting trot. The horses were wearing a dressage saddle with a fitting saddle tree and 4 different saddle pads (gel, leather, foam and reindeer fur) successively. For comparison, measurements were made without any saddle pad. Right forelimb motion was used to synchronise the pressure data with the stride cycles. A pressure mat was used under the saddle pad to collect the kinetic data. Maximum overall force (MOF) and the pressure distribution in longitudinal and transversal direction were calculated to identify differences between the measurements with and without saddle pads. RESULTS: A significant decrease in MOF was interpreted as improved saddle fit, and a significant increase as worsened saddle fit. Only the reindeer fur pad significantly decreased the MOF from 1005 N to 796 N at walk and from 1650 N to 1437 N at trot compared to without pad measurements. None of the saddle pads increased the MOF significantly when compared to the data without saddle pad. The pressure distribution in longitudinal and transversal direction was also improved significantly only by the reindeer fur pad at trot compared to no pad. CONCLUSION: This study demonstrated that a well chosen saddle pad can reduce the load on the horse's back and therefore improve the suitability of a fitting saddle.

A comparison of forces acting on the horse's back and the stability of the rider's seat in different positions at the trot.

The aim of the study was to compare the stability of the rider as well as the forces acting on a horse's back with different seating positions at the trot (sitting trot, rising trot and two-point seat). The same experienced rider was mounted on 10 sound horses trotting on a treadmill. The kinetic data were recorded with an electronic pressure mat, placed under a well-fitting dressage saddle with no saddle pad. The rider used three different seating positions, each for 20 s. Right forelimb motion was used to synchronise the pressure data with the stride cycles. To determine the rider's stability, the movement of the centre of pressure (COP) along the transverse (X) and longitudinal (Y) axes was calculated. The force was taken as the sum of all segments of the pressure pad multiplied by the area of the pressure pad. The maximum force and the X- and Y-deviations were evaluated using ANOVA for repeated measures with a Bonferroni Post hoc test. The stability of the rider in the Y-direction was significantly highest in the two-point seat, followed by the rising trot and the sitting trot, respectively. In the X-direction, there was no significant difference between the three positions. The significantly highest load on the horse's back was at the sitting trot (2112 N), followed by the rising trot (2056 N) and the two-point seat (1688 N). The rider was most stable in the two-point seat while transferring the lowest load on the horse's back. The rising trot was found to be more stable and less stressful for the horse's back compared to the sitting trot.

The influence of different saddle pads on force and pressure changes beneath saddles with excessively wide trees.

This study was performed to investigate the forces and pressure distribution under different saddle pads when an excessively wide saddle is used. Eighteen sound horses were ridden on a treadmill at walk and trot. The horses were equipped with a dressage saddle with an excessively wide saddle tree and four different pads (gel, leather, foam and reindeer-fur) used sequentially. For comparison, one measurement was made without a saddle pad. A pressure mat under the pad was used for the collection of kinetic data. Kinematics from the right fore-hoof were required to synchronise the data with the stride cycles. To identify any differences between measurements with and without saddle pads, the maximum overall force (MOF) and pressure distribution in longitudinal and transversal directions were calculated. The saddle pressures and MOF showed significant intra-horse effects. At walk, the foam and gel pads significantly reduced the MOF in 44.4% of cases, whereas at the trot, the gel and reindeer-fur pads significantly reduced MOF in 61.1% of subjects. The leather pad increased MOF in the highest number of horses at walk (27.8%) and trot (33.3%), although these results did not reach significance after inter-horse effects were included. The choice of a saddle pad to improve the fit of an excessively wide saddle should therefore be based on highly individual criteria for each horse.

Determination of the stiffness of the equine cervical spine.

This aim of this study was to test the hypothesis that the stiffness of the equine cervical spine depends on the direction of force applied and on spinal position. Muscles and nuchal ligament were removed from the cervical spines of 17 horses that were without a history of cervical or neurological disease. The cervical spines were then flexed/extended dorsoventrally (with the spine straight and with the occiput rotated 30° against T1) and laterolaterally. Mean dorsoventral stiffness was 297 N/m (± 135) in flexion, 1347 N/m (± 2083) in extension, 421 N/m (± 164) in lateral flexion, 279 N/m (± 93) in rotated flexion, and 386 N/m (± 191) in rotated extension. There was a positive correlation between the length of cervical spine and stiffness for dorsoventral flexion (r = 0.63; P < 0.01) and extension (r = 0.53; P < 0.05). The stiffness of the equine cervical spine depended on the direction of the loading and was 2-7 times less than thoracolumbar stiffness in horses.

Motion pattern analysis of gait in horseback riding by means of Principal Component Analysis.

As a consequence of the three interacting systems of horse, saddle, and rider, horseback riding is a very complex movement that is difficult to characterize by a limited number of biomechanical parameters or characteristic curves. Principal Component Analysis (PCA) is a technique for reducing multidimensional datasets to a minimal (i.e., optimally economic) set of dimensions. To apply PCA to horseback riding data, a "pattern vector" composed of the horizontal velocities of a set of body markers was determined. PCA was used to identify the major dynamic constituents of the three natural gaits of the horse: walk, trot, and canter. It was found that the trot is characterized by only one major component accounting for about 90% of the data's variance. Based on a study involving 13 horses with the same rider, additional phase plane analyses of the order parameter dynamics revealed a potential influence of the saddle type on movement coordination for the majority of horses.

Electromyographic activity of the longissimus dorsi muscles in horses when walking on a treadmill.

The pattern of electromyographic activity of the equine long back muscle at the walk has not yet been reported. The aim of this study was to use surface electromyography to measure activity of the longissimus dorsi muscles of horses walking on a treadmill. Fifteen horses without back pain were used and electromyographs were recorded bilaterally from the longissimus dorsi muscles at the level of T12, T16 and L3. Mean electromyograph activity and mean motion were calculated for each horse. At the walk, only one maximum activity for each longissimus dorsi muscle was detected during each motion cycle and this was highest at T12 and lowest at L3. Activity of the longissimus dorsi muscles at the walk is mainly responsible for stabilisation of the vertebral column against dynamic forces. At T12 the high maximum activity could contribute to the development of muscle pain at this site.

A novel method to estimate the stiffness of the equine back.

Diagnosis of back problems in equine orthopedics can be a difficult task. The aim of our study was to develop a new method for estimating the stiffness of the equine back in vivo. We measured the activity of the long back muscle at two locations on both sides at thoracic vertebrae T12 and T16 of 15 horses flexing and extending their back at stance using telemetric surface electromyography, while simultaneously recording the motion of the back with a video camera system. Out of these paired data sets we computed a transfer function in the frequency domain and evaluated its capability of capturing the biomechanical behavior. The transfer function was evaluated via correlation between calculated and actual motion resulting in correlation coefficients of 0.89 for lateral flexion and 0.83 for ventral extension at T16 and 0.82 for lateral flexion and 0.83 for ventral extension at T12. The transfer function was fitted to a filter polynomial of second order, and related to the motion equation. By comparison of coefficients we gained an estimate for the stiffness of the back resulting in a mean value of approximately 6100 N/m for lateral flexion and 650 N/m for ventral extension. This new method enables clinicians in equine orthopedics to estimate back stiffness in horses, and it also provides reality grounded values for biomechanical models of the equine back.

A pattern recognition approach for the quantification of horse and rider interactions.

REASONS FOR PERFORMING STUDY: Interactions of various systems were investigated in several studies of dynamic systems, but the interactions between horse and rider have not yet been documented. These interactions include the rider's ability to control the horse, adapt to the horse and maintain both participants' body position. An optimum interaction is also adapted to the individual nature of the horse. OBJECTIVE: To identify rider-horse interactions by means of artificial neural nets analysing the time-continuous pattern. METHODS: Fourteen horses were measured trotting on hand, and ridden at working trot with a professional and a recreational rider using a 3D high speed video system (120 Hz)1. Angles were calculated after low pass filtering (5-20 Hz). Horse movements were described by 2D angles, angular velocities, and angular accelerations of variables of the right body side: hind and front fetlock, head, back and the summation angle of carpus, elbow, and shoulder, the summation angle of hock, stifle, and hip. Distances between the trajectories of the feature vectors in an N = 11 x 11 Kohonen map were determined and analysed by means of a cluster analysis. RESULTS: Depending on the variables included, both rider specific as well as horse specific movement patterns could be identified. The time courses of the head angle indicate a movement pattern mainly dominated by the rider, whereas the time courses of variables of the hind fetlock and hock in most cases did not show differences between the conditions with, and without, rider. The skill of the professional rider could be documented with a higher adaptation to the horse's movement pattern. CONCLUSION AND POTENTIAL RELEVANCE: The presented time course oriented approach provides a sensitive tool in order to quantify the interaction of rider and horse.