Longeing Surface's Effects on Sound, Lame Horses

Does longeing surface really make that big of a difference in how a horse moves? One research team believes so, and they recently worked to determine exactly how surface affects a horse's movement.

When faced with a lame horse, veterinarians will typically perform a lameness examination. Many lameness exams include a longe line portion that allows the veterinarians to evaluate how the horse moves on a circle compared to how he moves on a straight line. This is particularly helpful in cases of mild lameness and when more than one limb is affected, said Thilo Pfau, PhD, a lecturer in bio-engineering at the Royal Veterinary College's Department of Clinical Science and Services, in London, England.

And, sometimes, veterinarians will evaluate the horse moving on both hard and soft surfaces, which Pfau said can help veterinarians distinguish between different "pathologies" (i.e., injuries affecting joints or bones vs. soft tissue injuries).

Does Movement Symmetry Equate to Soundness?

Researchers often evaluate horses' movement symmetry during scientific studies. But does movement symmetry equate to soundness?

"On the straight movement symmetry equates to soundness," said Thilo Pfau, PhD, a lecturer in bio-engineering at the Royal Veterinary College's Department of Clinical Sciences and Services. "On the circle it is a bit more tricky, since even sound horses do not move symmetrically since they lean into the circle.1,2

"It is essential to know how much asymmetry is normal on different surfaces in order then to be able to reliably spot horses that are ‘abnormal,’ " he continued. "For straight line we have started to establish ‘normal' ranges or thresholds (more needs to be done) but on the circle the data is pretty much nonexistent."

Erica Larson

1 Pfau T, Stubbs NC, Kaiser LJ, Brown LE, Clayton HM. Effect of trotting speed and circle radius on movement symmetry in horses during lunging on a soft surface. Am J Vet Res 2012;Dec;73(12):1890-9. 
2 Starke SD, Willems E, May SA, Pfau T. (2012): Vertical head and trunk movement adaptations of sound horses trotting in a circle on a hard surface. Vet J 2012 Jul;193(1):73-80. 

At the 2013 International Equine Conference on Laminitis and Diseases of the Foot, held Nov. 1-3 in West Palm Beach, Fla., Pfau presented recent research on the effects of longeing surface—hard or soft ground—on movement symmetry in sound horses as well as those with mild front-end lameness. Pfau and colleagues carried out a study aimed at:

  • Quantifying movement symmetry in sound horses longeing at the trot on hard and soft ground, and
  • Comparing movement symmetry between sound and mildly lame horses and determining if differences were greater with the affected limb on the inside or outside of the circle.

Pfau and colleagues fitted 23 horses—nine sound control horses, five with mild left front-limb lameness, and nine with mild right front-limb lameness—with an inertial gait analysis system that collects data using small sensors attached noninvasively to the horse's body. In Pfau's study, the team attached these sensors to the horse's poll, croup, and right and left hip bones. The device then transmitted information about the horse's motion symmetry to a laptop computer for the veterinarian to evaluate.

"We use full 6 degrees of freedom sensors that allow us to quantify orientation of the sensors, as well as linear accelerations in three directions," Pfau explained. "We then used this information to calculate true vertical movement of each landmark (sensor)."

Once they applied the gait analysis system, the team evaluated each horse trotting on a 10-meter circle in both directions, on hard and soft ground, in random order.

The team found that movement symmetry decreases in sound horses longeing on both hard and soft surfaces to a similar degree. Meanwhile, in the horses with mild front-end lameness, the team observed a more pronounced decrease in movement symmetry of the horses' head with the lame limb on the inside of the circle.

"The horses with mild forelimb lameness showed characteristic patterns of decreased symmetry, particularly when the affected limb was on the inside of the circle," Pfau concluded, adding that most horses appeared more lame (or asymmetrical) on the hard surface.

"There are distinct differences in movement symmetry patterns between sound and mildly lame horses when longed on soft and hard surfaces," Pfau told The Horse. "So always longe a horse with mild lameness on both surfaces to maximize your chances of establishing whether a horse has an underlying mild lameness.

"For the first time we now have quantitative evidence about the amount of changes in asymmetry in sound and lame horses on different surfaces," he added. "This provides us with essential baseline information for further studies that can then establish the exact differences between different types of injuries and for early detection of underlying subclinical lameness."

In the future, Pfau said, the sensitivity and specificity of movement symmetry on the longe should be identified in relation to diagnosing foot-related lameness problems. 

Disclaimer: Seek the advice of a qualified veterinarian before proceeding with any diagnosis, treatment, or therapy.