Leg Weights Help Rehabilitate Hind Limb Gait Issues
Unlike in human medicine, where physical therapy (PT) is widely embraced and an abundance of science supports the use of various PT techniques and tools, the science supporting PT in horses is lacking. This leaves veterinarians and horse owners alike wondering what works and what doesn't.
"In an attempt to provide a scientific basis for the use of PT and rehabilitation in the equine industry, I focused my research efforts on evidence-based research studies in this area," said Hilary Clayton, BVMS, PhD, MRCVS, Mary Anne McPhail Dressage Chair in Equine Sports Medicine at Michigan State University's College of Veterinary Medicine and Vice President of the American College of Veterinary Sports Medicine and Rehabilitation.
Clayton, together with equine physical therapist Narelle Stubbs, BAppSc (Phty), MAnimST (Animal Physiotherapy) of the Animal Rehabilitation Institute, in Loxahatchee, Fla., has published several studies assessing how PT might improve toe dragging and short striding in horses. In these studies researchers attached bracelets or light leg weights around horses' pasterns to stimulate receptors in the skin.
"This simulation results in activation of specific muscles that change the horse's movement pattern," Clayton explained. "With practice, these changes can reestablish normal coordination patterns and strengthen muscles that have become inactivated during lameness. Stimulation of the hind pastern results in a reflex response involving contraction of the hock muscles, which results in flexion of both the hock and stifle joints."
In one study published in the April 2010 edition of the Equine Veterinary Journal, Clayton and Stubbs stimulated horses' pastern skin using bracelets consisting of a loose strap with lightweight chains (less than 2 ounces) that brushed gently against the skin of the pastern and coronet as the hoof moved. Motion analysis showed that when the horses were wearing the bracelets the height of the hind hoof during the swing phase (i.e., when the foot is off the ground) increased as much as threefold at a trot due to increased flexion primarily at the stifle and hock joints.
"This (increased flexion) was due primarily to increased activation of the flexors and extensor muscles of the hock," Clayton relayed. "Thus, this technique appears beneficial for toe dragging, but because there was no change in hip flexion, this technique would not be expected to improve short striding."
In another study published in the March 2011 edition of the Equine Veterinary Journal the researchers evaluated using 24-ounce ankle weights wrapped around the hind pasterns.
"The response was similar to the bracelets in that increased flexion of the stifle and hock causing a threefold increase in hoof elevation in the swing phase was noted," Clayton said. "Unlike the bracelets, the flexor muscles had to work harder to overcome the greater resistance of the weighted limb and pull the hoof off the ground into the swing phase. Then, in late swing the extensor muscles have to work harder to slow the forward motion. Together these findings indicate that leg weights are useful for muscle strengthening."
Most recently, Clayton, Stubbs, and colleagues compared the effects of four different types of stimulation devices attached to the hind feet of trotting horses. These devices included loose, 10-gram straps, lightweight (55 grams) stimulators, a limb weight (700 grams), and a combination of a limb weight with a lightweight stimulator.
"We found that both the type and weight of the foot stimulators affected the hock and stifle joints differently, suggesting that different types of foot stimulators are appropriate for the rehabilitation of specific hind limb gait issues such as toe dragging and short striding," concluded Clayton. "We are now evaluating the value of trotting over rails as a way to activate the hip musculature and increase stride length."
The study, "Evaluation of biomechanical effects of four stimulation devices placed on the hind feet of trotting horses," was published in the November 2011 edition of The American Journal of Veterinary Research.
Disclaimer: Seek the advice of a qualified veterinarian before proceeding with any diagnosis, treatment, or therapy.
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