Modelling fore- and hindlimb peak vertical force differences in trotting horses using upper body kinematic asymmetry variables.

The research explores the differences in vertical force exerted by the fore and hind limbs of trotting horses and investigates the connection between these differences and the asymmetrical motion of the horse’s upper body (head, withers, and pelvis). The study indicates a significant interrelation between movement asymmetry and force exertion, potentially aiding diagnosis of lameness in horses.

Introduction and Hypothesis

• The introduction section highlights that vertical ground reaction force (dFz) differences in a horse’s contralateral forelimbs and hindlimbs are used to measure weight-bearing lameness. This research uses vertical movement asymmetries (VMA) of the horse’s upper body, a more commonly used and practical method, to study the same.
• The authors argue that understanding kinetic responses through kinematics can lead to better insights about quantified lameness—a condition affecting a horse’s ability to move normally.
• The study hypothesizes that VMA of a horse’s head, withers, and pelvis will have a significant influence on the dFz outcomes.

Methods

• The retrospective study uses data from 103 horses that displayed wide-ranging dFz from running on a force-measuring treadmill synced to an optical motion capture system.
• VMA and dFz data from the horses’ upper body were examined for this study. Multiple linear mixed models and linear regressions are applied to the kinematic variables, in an attempt to model the impact on dFz.

Results and Interpretation

• The results indicate a complex relationship between VMA and dFz, with both the intensity and timing of the VMA playing a crucial role.
• On average, the VMA contribution to dFz from different parts of the body was found to be 66% from the head, 76% from the withers, and 33% from the pelvis for the fore limbs, respectively. The hind limbs showed 34% contribution from the head, 24% from the withers, and 67% from the pelvis.
• The linear regressions used to model fore/hind limb dFz resulted in average measurement root mean squared errors of 0.83% and 0.82% dFz, respectively.

Conclusions

• The findings suggest that the upper-body VMA in horses is clinically meaningful for differentiating types of weight-bearing lameness, such as primary fore, hind, ipsilateral, and diagonal lameness.
• These results might provide a new perspective on diagnosing and treating lameness in horses, a condition that is often difficult to quantify.