Electrotherapy technology has been used since the 60’s to manage pain, improve range of motion, reverse atrophy (wastage) in muscles, decrease oedema (swelling), improve motor control, stimulate blood flow, making it a go-to for rehabilitation therapy in all veterinary medicine.
What is electrotherapy?
Electrotherapy is the use of electro stimulation – including neuromuscular electrical stimulation (NMES), transcutaneous electrical nerve stimulation (TENS) and interferential therapy – (IF) are forms of electrotherapy. Electro stimulation is useful for pain relief (TENS, IF) or for neural and muscular stimulation (NMES, IF).
The other broad types of electrotherapy are: ultrasound, laser and electromagnetic therapy. They are useful modalities used by physiotherapists to complement and support treatment.
How does electrotherapy work?
With electrotherapy you facilitate specific muscle contraction by stimulating specific motor neurons, or produce pain relief by stimulating sensory neurons.
Stimulation of these neurons creates depolarisation of the nerve cells membrane potential which creates an action potential known to us as a nerve impulse. This changes the state of the nerve from unpolarised to polarised, where it is then able to transmit messages to the brain or the periphery (the bodies extremities).
The polarised/depolarised state (which produces an action potential) is a natural occurrence in nerves throughout the body. However, when we use electro stimulation, this process is ‘generated artificially’. Whether the polarised/depolarised state occurs naturally or is manufactured using electrotherapy, the response of the nerves about a stimulus remains the same – this is one of the great benefits of electrotherapy.
A stronger stimulus increases the number of fibres being targeted, so your horse will feel or receive a stronger reaction.
Action and reaction
There is always a refractory period where the nerve cannot carry an action potential, which usually follows after depolarisation of the nerve (once a message is sent). The bigger the action potential generally the longer the refractory period. Electrotherapy is a non-invasive treatment and has few side effects.
Electrical stimulation can be used to excite sensory nerve “A-delta” fibres, which inhibit the transmission of the “C” fibres’ noxious stimulus, producing pain relief via a pain-gate mechanism.
Using conventional TENS with high frequency and pulse duration will achieve this pain relief mechanism. A further pain relief method is produced using acupuncture-like TENS set at higher intensity and lower pulse frequency. This produces a release of endogenous opioids producing pain relief at a segmental level, but this form of TENS is also slightly less tolerated than conventional TENS due to the higher intensity.
KINDS OF ELECTROTHERAPY DEVICES:
1. Transcutaneous Electrical Nerve Stimulation (TENS)
TENS produces sensory stimulation to “gate” the pain signal, while stimulating release of endogenous endorphins. A TENS device is often used for electroacupuncture, its action visible as continuous muscle twitches.
2. Interferential Electrotherapy
This is an alternative to TENS for suppressing pain. This device combines two higher frequency wave forms to create an interference pattern for sensory stimulation, but without visible twitching.
3. High-voltage, pulsed-current stimulators
These produce unidirectional continuous movement of ions, which can result in skin irritation and discomfort, but the user can reverse polarity with a switch, decreasing ion accumulation to improve discomfort, blood vessel dilation, and pain modulation through a rolling action of the muscles.
4. Neuromuscular Electrical Stimulators (NMES)
These provide a therapy technique that’s also called functional electrical stimulation (FES). A computer-generated signal replicates the normal motor neuron response, so it is tolerated well by the horse. The signal obtains benefits in superficial and deep tissues (up to 3-4 inches) and produces controlled muscle contractions with evident “on” and “off” muscle movements. FES activates both motor and sensory nerves to improve strength, manage spasms, improve range of motion, decrease edema, and increase blood and lymphatic flow.
5. Microcurrents
These mimic the electrical currents produced by the body to stimulate tissue healing. This electrotherapy
Benefits of Electrotherapy
- Reduce nerve pain.
- Promote healing of musculoskeletal injuries.
- Non-invasive, drug-free pain control.
- Prevent and reverses muscle atrophy.
- Increases circulation for wound repair.
- Improved circulation also reducing swelling and oedema.
- Has no side effects.