Equine Physical Therapy and Electrical Stimulators

Equine Physical Therapy and Electrical Stimulators

Photo: Pulse Signal Therapy

Physical therapy refers to the use of one or more physical approaches to promote and maintain the body's well-being, to help a horse recover from injury, and to re-educate an injured body part to move or function normally. Electrotherapy, in particular, is the application of an electric current via surface electrodes to produce controlled movement of the skin, muscle, tendon, and associated ligaments, explains Sheila Schils, PhD (biomechanics/kinesiology), a private equine rehabilitator in Wisconsin who reviewed the use of electrotherapy devices in horses at the 2009 American Association of Equine Practitioners annual convention. There are two main types of electrotherapy devices: sensory nerve or motor nerve stimulator.

Transcutaneous electrical nerve stimulators (TENS) These tools can be used to decrease pain by changing how the nervous system responds to pain signals. In general, TENS units send electrical signals that confuse the pain pathways, blocking the sensation of pain. These systems are designed to stimulate only sensory nerves.

Interferential stimulators These units also are nerve stimulators, but each uses a pair of high-frequency waves that can penetrate deeper into the skin than TENS units. Therapists use these stimulators to treat patients with debilitating pain. "Due to the very uncomfortable sensation of these stimulators, they should not be used for muscle stimulation, only very carefully used for nerve stimulation," says Schils.

Neuromuscular and functional electrical stimulators (FES) These units use electrical waves to stimulate motor nerves (i.e., nerves that control muscles). Thus, neuromuscular stimulators offer a way to mobilize muscles and associated tendons and ligaments through controlled muscular contractions, which can be uncomfortable for the horse. Ultimately, the deep muscle contractions these units induce reduce spasticity and the associated pain in the stimulated muscles. Unlike the TENS and interferential stimulators, this pain relief is long-lasting.

Galvanic muscle stimulators These units use direct current to generate a very low-voltage electrical signal to be transmitted in one direction. Professionals use this type of stimulus mainly to transmit substances, such as medications, through the skin in a process known as iontophoresis.

"These units can cause an unpleasant stinging sensation and can cause tissue trauma if used excessively, which limit their use," Schils explains.

Microcurrent electrical stimulators These units produce low-amplitude currents that mimic weak electrical currents produced during normal/natural tissue healing. Unlike TENS and neuromuscular electrical stimulators, these units do not stimulate sensory nerves or muscles, which means the patient feels no tingling.

Not all stimulators are appropriate for horses, despite their commercial availability. "Because the tissue mass of horses is greater than for humans, the tissues that need to be activated in horses are deeper and a specific type of waveform is necessary," Schils explains.

This means horses require a higher amplitude signal, but these increased signals could case irritation or trauma to the skin if the wrong device is selected or if the correct device is used inappropriately.

"Humans can rationalize the discomfort, whereas horses cannot," notes Schils. "An appropriate unit must be selected that will be tolerated by the horse without the need to administer a tranquilizer. Neuromuscular (FES) electrical stimulators appear to be most appropriate for horses because they produce controlled responses superficially as well as to the deeper tissues and are accepted by most horses."

About the Author

Stacey Oke, DVM, MSc

Stacey Oke, MSc, DVM, is a practicing veterinarian and freelance medical writer and editor. She is interested in both large and small animals, as well as complementary and alternative medicine. Since 2005, she's worked as a research consultant for nutritional supplement companies, assisted physicians and veterinarians in publishing research articles and textbooks, and written for a number of educational magazines and websites.

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