Massey University researchers are investigating limb injuries in racehorses by capturing the limbs’ 3D movement on camera and modeling it on computers.

Massey Equine Group’s Bob Colborne, BSc, MHK, PhD, and PhD student Alienor Bardin, a mechanical engineer, have funding from The New Zealand Equine Trust to tackle this problem.

“The various equestrian industries in New Zealand make up about 2% of the country’s (gross domestic product), and about a third of racehorses that start training and racing are retired and lost due to injury,” Colborne said. “About three-quarters of these are musculoskeletal injuries. These injuries, therefore, cause a fair amount of wastage, both in terms of the welfare impact on the horse and secondly, to the income potential. The purpose of our work is to assess the effects of variable ground surfaces on the forces applied to the limb during gait.”

The experimental work involves having the horses trot and canter along a runway in a sand arena over a force platform embedded in the surface in front of six infrared cameras that record the 3D movement of the horse’s limb segments on a consistent surface.

This baseline data allows the limb segments to be modeled and animated and allows an estimation of the forces applied to the ligaments and tendons. It can then be used to test the strain in ligaments and tendons when the limb is faced with variable footing and ground reaction forces—a softer, or harder than expected surface in the limb’s stance phase.

This will allow the researchers to determine whether racehorses are capable of responding to a sudden change in ground condition during the perturbed stance phase, or if the response is not until the following stance phase, at which point the ground surface might have changed back.

“The physical properties of equestrian riding and racing surfaces have been associated with limb injuries in horses, and most of the research in this area has focused on quantifying the surface’s ability to absorb the concussive landing and shear forces between the hoof and ground,” Colborne said.

“On soft ground, the surface absorbs the landing forces, and so the limb can afford to be relatively stiff. On a harder surface, the limb becomes more compliant so it can attenuate the concussive impacts and reduce the impact shocks to the limb,” he continued. “However, this compliance may come at a cost: If the distal joints are less supported by tendon tension, then disruptive perturbations caused by hard uneven ground may cause the hoof to twist on impact and result in ligament or joint damage.”