The Effect That Induced Rider Asymmetry Has on Equine Locomotion and the Range of Motion of the Thoracolumbar Spine When Ridden in Rising Trot.

The research study explores the impact of a rider’s asymmetry on a horse’s movement and the range of motion in the horse’s thoracolumbar spine when riding in a rising trot. The authors also discuss the immediate adjustments that horses make when faced with an asymmetric ride.

Methodology

• The study used a sample of ten non-lame horses.
• To investigate the effect of rider asymmetry, researchers simulated rider asymmetry by shortening one stirrup by 5 cm.
• To measure the movement of the horse and the rider, 2D kinematics joint center markers were used (Quintic Biomechanics).
• Additionally, horses were equipped with seven inertial sensors placed at various points on their bodies to monitor their movements and response to the induced rider asymmetry. These were located at the fifth and eighteenth thoracic vertebrae, third lumbar vertebra, tubera sacrale, and left and right tubera coxae.

Data Analysis

• The researchers used a mixed model for data analysis, with the horse as a random factor, and stirrup condition (symmetrical stirrups and asymmetrical stirrups), and the direction of the horse (inside and outside) were defined as fixed factors.
• Data from cases where the right stirrup was shortened was mirrored to represent scenarios with a shortened left stirrup.
• To identify distinct aspects between symmetrical and asymmetrical stirrup conditions, a significance cut-off level of P ≤ .05 was used.

Findings

• The study found that on the rein where the stirrup was shortened (on the outside), there was an increased range of lateral bending motion at T5, L3, and TS.
• There was also an increased mediolateral displacement or side-to-side movement at T5, T18, and L3.
• Increases in maximum fetlock extension of both the front and hind limbs on the side opposite to the shortened stirrup were noted.
• For the condition with the shortened stirrup on the inside, there were increases in the range of flexion-extension, axial rotation at T5 and lateral bending of T5, L3, and TS.

Conclusions

• The results suggest that asymmetry in rider posture has a tangible effect on the movements and mobility of the horse’s thoracolumbar spine.
• The authors recommended further research in this area to understand the long-term effects this may have on the horse’s overall locomotor health.