Force and pressure distribution beneath a conventional dressage saddle and a treeless dressage saddle with panels.

The objective of this study was to compare forces and pressure profiles beneath a conventional dressage saddle with a beechwood spring tree and a treeless dressage saddle without a rigid internal support and incorporating large panels and a gullet. The null hypothesis was that there is no difference in the force and pressure variables for the two saddles. Six horses were ridden by the same rider using the conventional dressage saddle and the treeless dressage saddle in random order and pressure data were recorded using an electronic pressure mat as the horses trotted in a straight line. The data strings were divided into strides with ten strides analyzed per horse-saddle combination. Variables describing the loaded area, total force, force distribution and pressure distribution were calculated and compared between saddles using a three-factor ANOVA (P<0.05). Contact area and force variables did not differ between saddles but maximal pressure, mean pressure and area with pressure >11kPa were higher for the treeless dressage saddle. The panels of the treeless dressage saddle provided contact area and force distribution comparable to a conventional treed saddle but high pressure areas were a consequence of a narrow gullet and highly-sloped panels. It was concluded that, even with a treeless saddle, the size, shape, angulation, and position of the panels must fit the individual horse.

Effect of trotting speed and circle radius on movement symmetry in horses during lunging on a soft surface.

OBJECTIVE: To determine whether body lean angle could be predicted from circle radius and speed in horses during lunging and whether an increase in that angle would decrease the degree of movement symmetry (MS). ANIMALS: 11 medium- to high-level dressage horses in competition training. PROCEDURE: Body lean angle, head MS, and trunk MS were quantified during trotting while horses were instrumented with a 5-sensor global positioning system-enhanced inertial sensor system and lunged on a soft surface. Speed and circle radius were varied and used to calculate predicted body lean angle. Agreement between observed and predicted values was assessed, and the association between lean angle and MS was determined via least squares linear regression. RESULTS: 162 trials totaling 3,368 strides (mean, 21 strides/trial) representing trotting speeds of 1.5 to 4.7 m/s and circle radii of 1.8 to 11.2 m were conducted in both lunging directions. Differences between observed and predicted lean angles were small (mean ± SD difference, -1.2 ± 2.4°) but significantly greater for circling to the right versus left. Movement symmetry values had a larger spread for the head than for the pelvis, and values of all but 1 MS variable changed with body lean angle. CONCLUSIONS AND CLINICAL RELEVANCE: Body lean angle agreed well with predictions from gravitational and centripetal forces, but differences observed between lunging directions emphasize the need to investigate other factors that might influence this variable. For a fair comparison of MS between directions, body lean angle needs to be controlled for or corrected with the regression equations. Whether the regression equations need to be adapted for lame horses requires additional investigation.

Evaluation of intersegmental vertebral motion during performance of dynamic mobilization exercises in cervical lateral bending in horses.

OBJECTIVE: To identify differences in intersegmental bending angles in the cervical, thoracic, and lumbar portions of the vertebral column between the end positions during performance of 3 dynamic mobilization exercises in cervical lateral bending in horses. ANIMALS: 8 nonlame horses. PROCEDURES: Skin-fixed markers on the head, cervical transverse processes (C1-C6) and spinous processes (T6, T8, T10, T16, L2, L6, S2, and S4) were tracked with a motion analysis system with the horses standing in a neutral position and in 3 lateral bending positions to the left and right sides during chin-to-girth, chin-to-hip, and chin-to-tarsus mobilization exercises. Intersegmental angles for the end positions in the various exercises performed to the left and right sides were compared. RESULTS: The largest changes in intersegmental angles were at C6, especially for the chin-to-hip and chin-to-tarsus mobilization exercises. These exercises were also associated with greater lateral bending from T6 to S2, compared with the chin-to-girth mobilization or neutral standing position. The angle at C1 revealed considerable bending in the chin-to-girth position but not in the 2 more caudal positions. CONCLUSIONS AND CLINICAL RELEVANCE: The amount of bending in different parts of the cervical vertebral column differed among the dynamic mobilization exercises. As the horse's chin moved further caudally, bending in the caudal cervical and thoracolumbar regions increased, suggesting that the more caudal positions may be particularly effective for activating and strengthening the core musculature that is used to bend and stabilize the horse's back.

Evaluation of biomechanical effects of four stimulation devices placed on the hind feet of trotting horses.

OBJECTIVE: To compare effects of 4 types of stimulation devices attached to the hind feet on hoof flight, joint angles, and net joint powers of trotting horses. ANIMALS: 8 clinically normal horses. PROCEDURES: Horses were evaluated under 5 conditions in random order: no stimulators, loose straps (10 g), lightweight tactile stimulators (55 g), limb weights (700 g), and limb weights with tactile stimulators (700 g). Reflective markers on the hind limbs were tracked during the swing phase of 6 trotting trials performed at consistent speed to determine peak hoof heights and flexion angles of the hip, stifle, tarsal, and metatarsophalangeal joints. Inverse dynamic analysis was used to calculate net joint energies. Comparisons among stimulators were made. RESULTS: Peak hoof height was lowest for no stimulators (mean ± SD, 5.42 ± 1.38 cm) and loose straps (6.72 ± 2.19 cm), intermediate for tactile stimulators (14.13 ± 7.33 cm) and limb weights (16.86 ± 15.93 cm), and highest for limb weights plus tactile stimulators (24.35 ± 13.06 cm). Compared with no stimulators, net tarsal energy generation increased for tactile stimulators, limb weights, and limb weights plus tactile stimulators, but only the weighted conditions increased net energy generation across the hip joint. CONCLUSIONS AND CLINICAL RELEVANCE: The type and weight of foot stimulators affected the magnitude of the kinematic and kinetic responses and the joints affected. These findings suggest that different types of foot stimulators are appropriate for rehabilitation of specific hind limb gait deficits, such as toe dragging and a short stride.

Center-of-pressure movements during equine-assisted activities.

We compared anteroposterior and mediolateral range of motion and velocity of the center of pressure (COP) on the horse's back between riders without disabilities and riders with cerebral palsy. An electronic pressure mat was used to track COP movements beneath the saddle in 4 riders without disabilities and 4 riders with cerebral palsy. Comparisons between rider groups were made using the Mann-Whitney test (p < .05). The two rider groups differed significantly in anteroposterior range of COP motion, mediolateral range of COP motion, and mediolateral COP velocity. Anteroposterior COP velocity did not differ between groups. The results suggest that measurements of COP range of motion and velocity are potentially useful for monitoring changes in balance as an indicator of core stability during equine-assisted activities.

Length and elasticity of side reins affect rein tension at trot.

This study investigated the horse's contribution to tension in the reins. The experimental hypotheses were that tension in side reins (1) increases biphasically in each trot stride, (2) changes inversely with rein length, and (3) changes with elasticity of the reins. Eight riding horses trotted in hand at consistent speed in a straight line wearing a bit and bridle and three types of side reins (inelastic, stiff elastic, compliant elastic) were evaluated in random order at long, neutral, and short lengths. Strain gauge transducers (240 Hz) measured minimal, maximal and mean rein tension, rate of loading and impulse. The effects of rein type and length were evaluated using ANOVA with Bonferroni post hoc tests. Rein tension oscillated in a regular pattern with a peak during each diagonal stance phase. Within each rein type, minimal, maximal and mean tensions were higher with shorter reins. At neutral or short lengths, minimal tension increased and maximal tension decreased with elasticity of the reins. Short, inelastic reins had the highest maximal tension and rate of loading. Since the tension variables respond differently to rein elasticity at different lengths, it is recommended that a set of variables representing different aspects of rein tension should be reported.

Pressure on the horse's withers with three styles of blanket.

The objective of this study was to compare total force and localised pressure on horses' withers with three blanket styles (straight cut, V-shaped insert, cutback withers). Three pressure recordings, each of 5s duration, were taken in order to determine blanket pressure on the withers during standing and walking in 12 horses. Means+/-SD were calculated for the following variables and compared across blankets: total force, mean pressure, maximal pressure, and area with pressure >4 kPa. For standing trials, the blanket with the V-shaped insert had the lowest total force and smallest area with pressure >4 kPa (P<0.05). For walking trials, the straight cut blanket had the highest total force, maximal pressure, mean pressure, and largest area with pressure >4 kPa (P<0.05). The results indicate that blanket style affects force and pressure on the horse's withers and that blankets may exert sufficient pressure on the withers to induce the formation of pressure sores.