Head and body centre of mass movement in horses trotting on a circular path.

The research investigates the movements of horse’s centre of mass (COM) when trotting in a circular path. The study examines the mechanics of these movements, forming a foundation for understanding the causes of injuries, responses to diagnostic techniques, and improvement of rehabilitation exercises.

Objectives

• The study aimed to develop a methodology for the kinematic analysis of horse movements when trotting along a circular trajectory.
• It sought to provide a descriptive report on the movements of the horse’s total body centre of mass (COMbody) during this activity.

Study Set-up

• The researchers placed seventy-five skin markers on five sound horses, spread across their heads, necks, trunks, and limbs.
• These markers were tracked in a global coordinate system at a frequency of 120 Hertz as the horses trotted around a small circle.
• Using the data on the horses’ segmental inertia, the three-dimensional positions of the segmental centres of mass and the COMbody were computed.

Observations and Findings

• The research found that the COMbody was high at the start and end of the diagonal stance phases and low at the mid-stance.
• All horses were observed to lean towards the inside of the circle, with a mean inclination angle of 14.8 +/- 2.8 degrees.
• In the transverse direction, the COMbody swung from side to side, with its most inward position around the time of contact of the inside forelimb and its most outward position around the time of contact of the outside forelimb.
• The same motion pattern for COMhead/neck in the transverse direction was observed for all horses, but the mean position relative to the circle line varied among them.

Conclusions

• The study concluded that horses tend to lean towards the inside when trotting around a small circle.
• The centres of mass for both the horse’s head/neck and the entire body displayed two vertical oscillations in each stride.
• There was a single mediolateral excursion that was asymmetrical to the inside and outside of the circle line.
• This study marked a crucial step towards understanding locomotion mechanics during turning, potentially helping prevent injuries, improve diagnostic methods, and enhance rehabilitation exercises.