Influence of functional rider and horse asymmetries on saddle force distribution during stance and in sitting trot

Asymmetric forces exerted on the horse's back during riding are assumed to have a negative effect on rider–horse interaction, athletic performance, and health of the horse. Visualized on a saddle pressure mat, they are initially blamed on a nonfitting saddle. The contribution of horse and rider to an asymmetric loading pattern, however, is not well understood. The aim of this study was to investigate the effects of horse and rider asymmetries during stance and in sitting trot on the force distribution on the horse's back using a saddle pressure mat and motion capture analysis simultaneously. Data of 80 horse-rider pairs (HRP) were collected and analyzed using linear (mixed) models to determine the influence of rider and horse variables on asymmetric force distribution. Results showed high variation between HRP. Both rider and horse variables revealed significant relationships to asymmetric saddle force distribution (P < .001). During sitting trot, the collapse of the rider in one hip increased the force on the contralateral side, and the tilt of the rider's upper body to one side led to more force on the same side of the pressure mat. Analyzing different subsets of data revealed that rider posture as well as horse movements and conformation can cause an asymmetric force distribution. Because neither horse nor rider movement can be assessed independently during riding, the interpretation of an asymmetric force distribution on the saddle pressure mat remains challenging, and all contributing factors (horse, rider, saddle) need to be considered

A mortar method for the coupled Stokes-Darcy problem using the MAC scheme for Stokes and mixed finite elements for Darcy

A discretization method with non-matching grids is proposed for the coupled Stokes-Darcy problem that uses a mortar variable at the interface to couple the marker and cell (MAC) method in the Stokes domain with the Raviart-Thomas mixed finite element pair in the Darcy domain. Due to this choice, the method conserves linear momentum and mass locally in the Stokes domain and exhibits local mass conservation in the Darcy domain. The MAC scheme is reformulated as a mixed finite element method on a staggered grid, which allows for the proposed scheme to be analyzed as a mortar mixed finite element method. We show that the discrete system is well-posed and derive a priori error estimates that indicate first order convergence in all variables. The system can be reduced to an interface problem concerning only the mortar variables, leading to a non-overlapping domain decomposition method. Numerical examples are presented to illustrate the theoretical results and the applicability of the method

Automated glycan assembly of a S. pneumoniae serotype 3 CPS antigen

Vaccines against S. pneumoniae, one of the most prevalent bacterial infections causing severe disease, rely on isolated capsular polysaccharide (CPS) that are conjugated to proteins. Such isolates contain a heterogeneous oligosaccharide mixture of different chain lengths and frame shifts. Access to defined synthetic S. pneumoniae CPS structures is desirable. Known syntheses of S. pneumoniae serotype 3 CPS rely on a time-consuming and low-yielding late-stage oxidation step, or use disaccharide building blocks which limits variability. Herein, we report the first iterative automated glycan assembly (AGA) of a conjugation-ready S. pneumoniae serotype 3 CPS trisaccharide. This oligosaccharide was assembled using a novel glucuronic acid building block to circumvent the need for a late-stage oxidation. The introduction of a washing step with the activator prior to each glycosylation cycle greatly increased the yields by neutralizing any residual base from deprotection steps in the synthetic cycle. This process improvement is applicable to AGA of many other oligosaccharides

Determining Objective Parameters to Assess Gait Quality in Franches-Montagnes Horses for Ground Coverage and Over-Tracking - Part 1: At Walk

Ground coverage and over-tracking are two gait quality traits describing the forward movement of the front respectively the hind limbs in relation to stride length and over-tracking distance. To investigate the complex interplay of different movement patterns in ground coverage and over-tracking, limb and body kinematics of 24 Franches-Montagnes (FM) stallions were measured with 3D optical motion capture (OMC) on a treadmill during an incremental speed test at the walk (1.4-2.0 m/s). The significance and amount of explained variance of kinematic parameters on stride length and over-tracking distance were estimated using linear mixed-effect models, with speed and horse as random effects. Two separate models were tested: a full model with all parameters measurable by OMC, and a reduced model with a subset of parameters also measurable with inertial measurement units (IMUs). The kinematic parameters were correlated to the subjective scores from six breeding experts to interpret their external validity. The parameter for ground coverage at the walk, explaining most of the variance in stride length, were the maximal forelimb retraction angle (11%) measured with OMC, and the range of pelvis pitch (10%) if measuring with IMUs. The latter was also the most relevant for quantifying over-tracking, explaining 24% to 33% of the variance in the over-tracking distance. The scores from most breeding experts were significantly correlated (r ≥ |0.41|) with the fore- and hind limb protraction angles, which reflect the textual definition of ground coverage and over-tracking. Both gait quality traits can be objectively quantified using either OMC or IMUs

Ground Reaction Forces: The Sine Qua Non of Legged Locomotion

Legged locomotion results from the feet pressing against the ground to generate ground reaction forces (GRFs) that are responsible for moving the body. By changing limb coordination patterns and muscle forces, the GRFs are adjusted to allow the horse to move in different gaits, speeds, and directions with appropriate balance and self-carriage. This article describes the typical GRF patterns in each gait, the adaptations that produce turning, and the GRF patterns used to unload the painful limb when the horse is lame. The intent is to provide information that is of practical interest and value to equine scientists rather than being a comprehensive review of the topic. [Abstract copyright: Copyright © 2019 Elsevier Inc. All rights reserved.

Withers vertical movement asymmetry in dressage horses walking in different head -neck positions with and without riders

The superimposed influences of different head and neck positions (HNPs) and rider effects on symmetry in sound horses have not been studied. Our aim was to investigate the effects of HNPs and rider on thesymmetry in minimum height of the withers at the walk. Seven high-level dressage horses were studied with and without rider in six HNPs: HNP1, free position; HNP2, dressage competition position; HNP3,flexed poll position; HNP4, over-flexed position; HNP5, extended raised position; and HNP6, forward downward position. Kinematic and vertical ground reaction force data were recorded during 15 s trialson an instrumented treadmill. In mixed models, difference in the minimal height of the withers in earlyleft vs right forelimb stance was modelled as dependent variable. The more restricted HNP3 (T-values2.62 to 1.98, 118 DF,P¼0.001 to<0.05) and HNP5 (P¼0.002 to<0.05) were generally less symmetrical while unridden and more symmetrical while ridden, compared with the free (HNP1) or forward downward (HNP6) positions. Both with and without rider, when the withers dropped lower in earlystance of one forelimb, this was associated with shorter protraction at the start of stance in the ipsilateral hind limb, and shorter stance overlaps between this hind limb and the other limbs during diagonalsupport, 3-limb support with two forelimbs and one hind limb, and ipsilateral support. HNP effects on withers movement asymmetry differed between unridden and ridden conditions. The considerablevariation between horses stresses the need for trainers to use individualized training programs to address horse asymmetry