Sagittal plane ground reaction forces, centre of pressure and centre of mass in trotting horses.

The study examines the forces exerted by trotting horses on the ground, specifically their forelimb and hind limb ground reaction forces, and the spatial relationship between two important balance points, center of pressure and center of mass. It provides a detailed picture of a horse’s physical interplay with the ground during the trot, by simultaneously measuring these factors in three trials with eight horses.

Study Design and Measurements

• The research was conducted on eight horses undertaking a trotting motion.
• Three trials were run to ensure consistency and precision of the recorded data.
• The researchers employed the use of four force plates to measure ground reaction forces which record the force exerted by the body onto the ground.
• The front limb and hind limb ground reaction forces were specifically recorded during these trials.
• Complementary to this, the center of pressure (COP) and center of mass (COM) were calculated. The COP is the point on the object where the resultant force acts, while the COM is the point where all the mass of the body can be considered to be concentrated.

Findings

• During the horse’s trot, the peak total vertical force was found to coincide with a zero total longitudinal force. This means when the force applied by the horse on the ground was at its maximum, there was no force being applied in the forward or backward direction.
• The COP was initially located at whichever hoof of the horse touched the ground first. However, it maintained a fairly constant position against the base of support during the middle part of the horse’s stance, before moving forward towards the fore hoof in the final third of stance.
• The COM moved forward continuously. It slowed (its longitudinal velocity decreased) with the braking force in early stance and increased with the propulsive force in late stance.
• The COM was found to be behind the COP during early stance, coincident at 35.8 ± 4.4% stance, and was furthest ahead at 67.6 ± 4.8% stance. This indicates that the horse’s center of mass moves in relation to its center of pressure as it trots, affecting the balance.
• These changes in the spatial relationship between COP and COM affected the moment arms of the forelimb and hind limb ground reaction forces – the distance between the application point of the force and the pivot point – and their effect in generating a pitching torque, or rotational movement, around the COM.

Ideal Applications and Long-term Impacts

This study could provide a deeper understanding of the horse’s physical dynamics during a trot, which could be utilized by veterinarians and therapists to develop more effective treatments for locomotion related illnesses or injuries in horses. This can also help trainers in sculpting a training program that’s in harmony with a horse’s natural movements, minimizing the risks of physical strain or injury.