Kinematics of the equine back: flexion-extension movements in sound trotting horses.

The study investigates the flexion-extension movements of horse’s back while trotting, using a 3-D kinematic analysis system. The findings indicate a highly repeatable temporal pattern in these movements, and suggest that the horse’s trunk muscles play a critical role in limiting these movements rather than inducing them.

Research Methodology

• The study involved a sample size of thirteen clinically sound horses.
• Five skin markers were placed on the horse’s dorsal midline as reference points during the trotting phase.
• A 3-D kinematic analysis system was used to record the movements of these horses while trotting.
• The movements were analysed under the conditions of a standard lameness examination.
• Three distinct back angles — thoracic, thoracolumbar, and lumbosacral — were calculated based on the positions of the skin markers.
• The recorded data underwent a Fourier series filtration for analysis.

Findings of the Study

• The study found that during the first part of each diagonal stance phase, the horses’ back extended, but during the second part, it flexed.
• The overall range of motion discovered during these flexion-extension movements was less than four degrees for each of the three calculated back angles.
• The researchers found both intra- and inter-individual variabilities in these movements. However, the values for the time points of maximal flexion and extension were quite low, reflecting a high degree of repeatability in the horses’ movements.
• The study also found more variability between different horses’ back mobility than between different trials of trotting by the same horse.

Interpretation and Implications

• This consistency in the temporal pattern of these flexion-extension movements suggests that the horses’ trunk muscles play a major role in the regulation of movement. The muscles seem to work more towards limiting these movements rather than contributing to or initiating them.
• These findings provide potentially useful insights into understanding the equine locomotion which is essential for improving performance and injury prevention in the field of equine sports.