Researchers in the United Kingdom recently examined kinematic differences—essentially, differences in how horses move—between collected and medium/extended trot in dressage horses to better understand the effect of collected versus lengthened paces, footing surfaces, and differences between young and mature dressage horses.

The team evaluated 20 clinically sound horses in active dressage training on two composite (sand/felt fiber/grain rubber) surfaces typical of dressage arenas. The researchers separated the horses into two groups: horses six years and under working at elementary and medium dressage levels, assessed at collected and medium trot; and horses nine years and over working at Prix St. Georges and above, assessed at collected and extended trot.

The team used 2-D high-speed motion capture to measure forelimb and hind-limb angles at midstance (the moment the horse has two feet on the ground), where peak load occurs. This phase of the gait is characterized by shoulder/elbow flexion and knee/fetlock extension in the forelimbs and hip/stifle/hock flexion with fetlock extension in the hind limbs.

Both young and mature horses showed reduced speed and stride length, coupled with increased stride duration, in collected trot compared with medium and extended trot. Both groups exhibited increased fetlock extension in medium and extended trot in the front and hind legs. These changes were greater in the mature horse group than in the young horse group. Knee and shoulder angles were associated with forelimb fetlock angle. Pace changes did not affect hock angle significantly. The different surfaces had no effect on fetlock or hock angles in any horses.

“The findings of the study help us understand more about what is happening to the horse’s limbs during collected, medium, and extended trot in a field-based scenario,” said Vicki Walker, BSc, MSc, of the Animal Health Trust’s Centre for Equine Studies, in Newmarket. “Our findings suggest that as the trot pace is lengthened, the horse has increased fetlock extension in its forelimbs and hind limbs and that could have an influence on the strain placed on the soft tissues of the limb, such as the suspensory apparatus, which is commonly injured in dressage horses.

“We would like to investigate this further in more and less extravagantly moving horses to see if the horses with ‘big extended trot’ movement show more difference between paces,” she continued, also noting a need for further investigation into differences between canter paces.

Walker said the fact that young and mature horses showed similar biomechanical differences between collected and lengthened paces suggests that the variations are present regardless of the horse’s age or training level, so the study results are likely applicable across the dressage horse population.

“These findings suggest that it may be sensible to try and avoid spending long periods of time in lengthened paces, especially if the horse is getting tired,” to avoid undue stress on internal structures, she added.

This study, “Comparison of limb kinematics between collected and lengthened (medium/extended) trot in two groups of dressage horses on two different surfaces,” was published in Equine Veterinary Journal