Forelimb kinematics and net joint moments during the swing phase of the trot.

The research investigates the force exerted at the joints of a horse’s forelimb during its trotting motion. The study combines kinematic data with morphometric data to calculate these forces and reveals that they vary according to the swinging phase and joint location.

Methods

• The study involved five healthy Warmblood horses. Their trotting was recorded using an optoelectronic system for three strides at an average velocity of 3.03+/-0.16 m/s.
• The researchers used a link segment model to calculate net force moments at various joints in the horse’s forelimb. This model combined kinematic data (movement specifics) with morphometric data (physical measurements).
• The model also included corrections for skin displacement, meaning the external movement of the horse’s skin over its skeletal structure during motion was accounted for.

Findings

• The force moments were found on the cranial/dorsal side at the beginning of the swing phase, and on the caudal/palmar side during the latter part. The transition time when force moments switched sides ranged from 35% to 52% of the swing phase.
• The highest net joint moments decreased from the proximal limb (nearer to the body of the animal) to the distal direction (further from the body).
• Published electromyographic (EMG) data, which records muscular activity, was found to correlate with the timing of the force moments, suggesting that the latter successfully reflect the muscular activity involved in trotting.
• During the early 30-40% of the swing phase, muscular activity indicated the acceleration of the limb. During the later stages, the muscular activity decelerated the forward swing of the upper limb.
• The low net joint moments at the distal joints during the first half of the swing suggest that their motion is primarily maintained by inertia.
• During the last half of the swing, increased flexor muscle activity signifies active control of the trotting motion, in preparation for landing back onto the ground.

Implications

• This research provides valuable insights into the internal movement dynamics of horses during trotting. It could potentially assist in the design of training protocols, therapeutic interventions, and the improvement of horse-riding equipment.
• The findings could also contribute to veterinary medicine, particularly in the diagnostic assessment of equine locomotor diseases or dysfunctions.