THE INFLUENCE OF THE RIDER ON THE TROTTING MOTION OF A HORSE

Introduction: The characteristics of trot, such as collection, impulsion, action of the hind quarter, the position of the head and the balance of the horse are described in the Rules of Dressage Events of the Federation Equestre International. Up to now, these characteristics were judged subjectively by dressage judges, but no objective measures have been developed to substantiate these judgments. The aim of our study was to establish measurable criteria that make possible the quantification of dressage characteristics, by comparing the motion pattern of trotting horses ridden by two riders of different skill and being led on hand. Materials and Methods: Twenty horses aged 4 to 22 years at different training levels were measured being ridden at trot by a professional rider and a hobby rider, as well as being trotted on hand. The measurements were carried out from the right side, with six cameras (sample rate 120 Hz, resolution 240 x 833 points) tracing 20 reflecting spherical markers placed on the horse’s and rider’s right side. At least eight recordings of five seconds each were taken with the ExpertVision System of Motion Analysis Corporation with the horse trotting on a 12 m long pressed sand track in an indoor riding arena. At least eight motion cycles of each rider-horse combination and of the horses being trotted on hand were analyzed. The 3-dimensional movement of the markers was calculated, and the stridelength, speed, and vertical movement of the fetlock joints were compared. The data were normalized to the trotting speed. The normal distribution of each group was tested using the Kolmogorov- Smirnov test, and the Student test of paired samples was used to check the differences between the means of the groups of the above described parameters. Results and Discussion: With the hobby rider the horses had the significantly lowest trotting speeds, the smallest stride length, the highest head position, the smallest vertical movement of the fetlock joint and the longest duration of stancephase when compared to when the horse is ridden by the professional rider and trotted on hand. Between the horse’s motion when ridden by the professional rider and trotted on hand no significant differences could be detected in the trotting speed and the duration of stance-phase, whereas significant differences were established for head position and stride length. The vertical movement of the fetlock joint did not differ significantly when ridden by the hobby rider and trotted on the hand, but both did differ significantly from the vertical movement of the fetlock joint when ridden by the professional rider. The results of this study show that some terms used by the Federation Equestre International can be translated into measurable quantities, and thus a more objective judgment of dressage may evolve

MOTION PATTERN CONSISTENCY OF THE RIDER-HORSE SYSTEM

INTRODUCTION: Dressage riding is difficult to judge, because the aesthetics of the performance cannot be measured simply. The aim of this study was to show a method of visualizing and quantifying the harmony of the motion of a rider and a horse by evaluating their coordination. Rider and horse have a natural frequency when trotting; they can therefore be considered a system of coupled biological oscillators. The characteristics of such a system are determined by the innate and learned motion patterns, anatomy and physical condition of both participants. Any periodic motion can be described as a limit-cycleattractor in the phase space. The characteristics of an oscillator or a system of oscillators can be depicted as a phase plane diagram (PPD), which is a suitable method to visualize the characteristics (e.g., longterm behavior and limit-cycle) of a complex system, such as the ridden horse. METHODS: Twenty horses aged 4 to 22 years on different training levels were measured being ridden at trot by a professional rider and a hobby rider. The measurements were carried out from the right side, with six cameras (sample rate 120 Hz, resolution 240 x 833 points) tracing 20 reflecting spherical markers placed on the horse’s and rider’s right side. At least eight recordings of five seconds each were taken with the ExpertVision System of the Motion Analysis Corporation with the horse trotting on a 12 m long pressed sand track in an indoor riding arena. At least eight motion cycles of each rider-horse combination were analyzed. The 3-dimensional movements of the markers were used to deduce the angle between the linkages of rider’s head to rider’s back and of rider’s back to the horse’s head. Then the data were normalized to 100% of the length of the motion cycle. Angle velocity and angle acceleration were computed and from all three data-sets, scaled to 100% of the professional rider’s angle, angle velocity and angle acceleration; the trajectories in the phase-space were plotted and the lengths of the resulting vectors (LV) in the phase-space were computed. The mean and average deviation (variation of LV) of LV of every horse and rider were determined and grouped for each rider. The normal distribution of each group was tested with the Kolmogorov-Smirnov test. The Student test of paired samples and one-way analysis of variance were used to check the differences between the mean of the groups of LV and average deviation. RESULTS AND DISCUSSION: There was no significant difference in the mean of LV between the 2 riders, but there was a significant () difference in the average deviation of the LV, showing that the motion of the horse-professional rider system is more consistent than of the horse-hobby rider system. With this method the rhythm and the natural balance of the rider-horse system can be evaluated, and this information might prove a useful feedback for the education of riders

The effect of induced forelimb lameness on thoracolumbar kinematics during treadmill locomotion

Reasons for performing study: Lameness has often been suggested to result in altered movement of the back, but there are no detailed studies describing such a relationship in quantitative terms. Objectives: To quantify the effect of induced subtle forelimb lameness on thoracolumbar kinematics in the horse. Methods: Kinematics of 6 riding horses was measured at walk and at trot on a treadmill before and after the induction of reversible forelimb lameness grade 2 (AAEP scale 1-5). Ground reaction forces (GRF) for individual limbs were calculated from kinematics. Results: The horses significantly unloaded the painful limb by 11.5% at trot, while unloading at walk was not significant. The overall flexion-extension range of back motion decreased on average by 0.2° at walk and increased by 3.3° at trot (P<0.05). Changes in angular motion patterns of vertebral joints were noted only at trot, with an increase in flexion of 0.9° at T10 (i.e. angle between T6, T10 and T13) during the stance phase of the sound diagonal and an increase in extension of the thoracolumbar area during stance of the lame diagonal (0.7° at T13, 0.8° at T17, 0.5° at L1, 0.4° at L3 and 0.3° at L5) (P<0.05). Lameness further caused a lateral bending of the cranial thoracic vertebral column towards the lame side (1.3° at T10 and 0.9° at T13) (P<0.05) during stance of the lame diagonal. Conclusions: Both range of motion and vertebral angular motion patterns are affected by subtle forelimb lameness. At walk, the effect is minimal, at trot the horses increased the vertebral range of motion and changed the pattern of thoracolumbar motion in the sagittal and horizontal planes, presumably in an attempt to move the centre of gravity away from the lame side and reduce the force on the affected limb. Potential relevance: Subtle forelimb lameness affects thoracolumbar kinematics. Future studies should aim at elucidating whether the altered movement patterns lead to back and/or neck dysfunction in the case of chronic lameness

Novel Methods for Surface EMG Analysis and Exploration Based on Multi-Modal Gaussian Mixture Models

<div><p>This paper introduces a new method for data analysis of animal muscle activation during locomotion. It is based on fitting Gaussian mixture models (GMMs) to surface EMG data (sEMG). This approach enables researchers/users to isolate parts of the overall muscle activation within locomotion EMG data. Furthermore, it provides new opportunities for analysis and exploration of sEMG data by using the resulting Gaussian modes as atomic building blocks for a hierarchical clustering. In our experiments, composite peak models representing the general activation pattern per sensor location (one sensor on the long back muscle, three sensors on the gluteus muscle on each body side) were identified per individual for all 14 horses during walk and trot in the present study. Hereby we show the applicability of the method to identify composite peak models, which describe activation of different muscles throughout cycles of locomotion.</p></div

Extended Thromboprophylaxis with Betrixaban in Acutely Ill Medical Patients

Background Patients with acute medical illnesses are at prolonged risk for venous thrombosis. However, the appropriate duration of thromboprophylaxis remains unknown. Methods Patients who were hospitalized for acute medical illnesses were randomly assigned to receive subcutaneous enoxaparin (at a dose of 40 mg once daily) for 10±4 days plus oral betrixaban placebo for 35 to 42 days or subcutaneous enoxaparin placebo for 10±4 days plus oral betrixaban (at a dose of 80 mg once daily) for 35 to 42 days. We performed sequential analyses in three prespecified, progressively inclusive cohorts: patients with an elevated d-dimer level (cohort 1), patients with an elevated d-dimer level or an age of at least 75 years (cohort 2), and all the enrolled patients (overall population cohort). The statistical analysis plan specified that if the between-group difference in any analysis in this sequence was not significant, the other analyses would be considered exploratory. The primary efficacy outcome was a composite of asymptomatic proximal deep-vein thrombosis and symptomatic venous thromboembolism. The principal safety outcome was major bleeding. Results A total of 7513 patients underwent randomization. In cohort 1, the primary efficacy outcome occurred in 6.9% of patients receiving betrixaban and 8.5% receiving enoxaparin (relative risk in the betrixaban group, 0.81; 95% confidence interval [CI], 0.65 to 1.00; P=0.054). The rates were 5.6% and 7.1%, respectively (relative risk, 0.80; 95% CI, 0.66 to 0.98; P=0.03) in cohort 2 and 5.3% and 7.0% (relative risk, 0.76; 95% CI, 0.63 to 0.92; P=0.006) in the overall population. (The last two analyses were considered to be exploratory owing to the result in cohort 1.) In the overall population, major bleeding occurred in 0.7% of the betrixaban group and 0.6% of the enoxaparin group (relative risk, 1.19; 95% CI, 0.67 to 2.12; P=0.55). Conclusions Among acutely ill medical patients with an elevated d-dimer level, there was no significant difference between extended-duration betrixaban and a standard regimen of enoxaparin in the prespecified primary efficacy outcome. However, prespecified exploratory analyses provided evidence suggesting a benefit for betrixaban in the two larger cohorts. (Funded by Portola Pharmaceuticals; APEX ClinicalTrials.gov number, NCT01583218. opens in new tab.

Course of serum amyloid A (SAA) plasma concentrations in horses undergoing surgery for injuries penetrating synovial structures, an observational clinical study

Abstract Background Injuries penetrating synovial structures are common in equine practice and often result in septic synovitis. Significantly increased plasma levels of serum amyloid A (SAA) have been found in various infectious conditions in horses including wounds and septic arthritis. Plasma SAA levels were found to decrease rapidly once the infectious stimulus was eliminated. The purpose of the current study was to investigate the usefulness of serial measurements of plasma SAA as a monitoring tool for the response to treatment of horses presented with injuries penetrating synovial structures. In the current study plasma SAA concentrations were measured every 48 hours (h) during the course of treatment. Results A total of 19 horses with a wound penetrating a synovial structure were included in the current study. Horses in Group 1 (n = 12) (injuries older than 24 h) only needed one surgical intervention. Patients in this group had significantly lower median plasma SAA levels (P = 0.001) between 48 h (median 776 mg/L) and 96 h (median 202 mg/L) after surgery. A significant decrease (P = 0.004) in plasma SAA levels was also observed between 96 h after surgery (median 270 mg/L) and 6 days (d) after surgery (median 3 mg/L). Four horses (Group 2) required more than one surgical intervention. In contrast to Group 1 patients in Group 2 had either very high initial plasma concentrations (3378 mg/L), an increase or persistently high concentrations of plasma SAA after the first surgery (median 2525 mg/L). A small group of patients (n = 3) (Group 3) were admitted less than 24 h after sustaining a wound. In this group low SAA values at admission (median 23 mg/L) and peak concentrations at 48 h after surgery (median 1016 mg/L) were observed followed by a decrease in plasma SAA concentration over time. Conclusions A decrease in plasma SAA concentrations between two consecutive time points could be associated with positive response to treatment in the current study. Therefore, serial measurements of plasma SAA could potentially be used as an additional inexpensive, quick and easy tool for monitoring the treatment response in otherwise healthy horses presented with injuries penetrating synovial structures. However further studies will be necessary to ascertain its clinical utility

The presence of long spinal muscles increases stiffness and hysteresis of the caprine spine in-vitro

Long muscle-tendon-units are known to contribute to spinal stiffness and hysteresis in-vivo, yet their contribution as a passive structure in-vitro is less well defined. Twelve full length caprine spines including the head, pelvis and all spinal muscles were tested during displacement in Flexion-Extension (FE) and coupled Lateral and Rotational (LR) motion in a material testing machine. Hysteresis and modified stiffness (modST), i.e. mean force divided by the total displacement, were calculated. This was repeated following removal of dorsal muscles (longissimus dorsi and gluteus) and ventral muscles (iliopsoas), in a random order. ModST and hysteresis in the different dissection stages were identified. Correlations between modST, hysteresis, body mass, spine length and longissimus muscle thickness were calculated. Removal of dorsal musculature reduced extension modST significantly by 23%, and flexion modST by 40%. Ventral muscle removal reduced extension modST by 1% and flexion modSt by 13%. Hysteresis was reduced by 27% after dorsal and 2% after ventral muscle removal in FE hysteresis. Out of 105 correlation coefficients, five values were significantly correlated (p<0.05, range r2: 0.61–0.71) and 10 values were highly significantly correlated (p<0.01, range r2: 0.75–0.97). Strongest correlations were between hysteresis and modST for the same movement direction and dissection state. The results of this study demonstrate that the presence of muscles stiffens the spine with dorsal muscles showing more effect. This supports the concept that muscle volume even in a non-contractile state provides a stabilising function to the spine