Electrical stimulation: what is it?

Electrical stimulation comes in many forms. Electrical Muscle Stimulation (EMS), Neuromuscular Electrical Stimulation (NMES), Transcutaneous Elecrical Nerve Stimulation (TENS), Electromyostimulation, and Functional Electrical Stimulation (FES) are the most common forms. There are slight differences, but the main concept is the same. In short, electrical stimulation works like this. As a start, an electrical stimulator sends an electric signal through its wires to its electrodes.

electrical stimulation electrodes
electrical stimulation electrodes

The electrodes can either be placed within the body, implanted through surgery, or onto the skin through sticky or rubber electrodes, as in the picture. Once the electric signal reaches the electrode, the signal stimulates the nearest nerves. From here, the signal acts as a so-called action potential: a signal that usually starts in the brain and is sent to the muscles through the nerves. This action potential causes the muscle(s) that are attached to this nerve to contract, which makes the body move. This way, the electrical stimulator serves as an external ‘brain’ that can initiate movement. This mainly becomes useful when something’s wrong between your own brain and your own muscles. Electrical stimulation is a proven tool for helping people with motor disabilities, for example for people who have had a stroke, spinal cord injury, MS, Parkinson,  .

History and future of electrical stimulation

Electrical stimulation has been around for a long time. I can’t exactly tell you when this was. But the story does go that people would use electric fish to fight pain and make muscles move back in the days. The frequent use of ES for beneficial effects after injuries or diseases, however, came around much later. A lot of research has been carried out in the meantime, especially during the last 60 years. Thanks to the results of this research, electrical stimulation has become accepted in rehabilitative therapies more and more and it is now being used for rehabilitation in many countries. However, much more is possible with electrical stimulation. This is shown by the results of many studies.

For example, studies have been performed in which paralysed people were able to walk again voluntarily with the assistance of electrical stimulation and a machine that recorded the signals of the brain and sent these to the electrodes on their legs. You can look at this as if it is a ‘wireless external nerve’. This technique is called a Brain Machine Interface, click the link to read more about it.

Another tactic for improving the functional capabilities of people is to make use of the EMG-signals produced by their muscles. Research to the improvement of these functional properties, as well as to other health-related properties, is executed every day. This promises improved therapies for improving health in the future.

If you would directly like to know how to apply electrical stimulation, hit the link. Also always carefully read the manual that comes with your stimulator before applying ES. Furtherly, make sure to check out when not to use electrical stimulation before doing anything with it.

Electrical stimulation and rehabilitation

Electrical stimulation is being used in rehabilitation for multiple purposes. Electrical stimulation has proven to be effective for, among others, patients with (complete and incomplete) spinal cord injuries, strokes, multiple sclerosis, Parkinson’s disease, cerebral palsy, and after coma. Think of safely reducing muscles spasms, increasing muscle mass, improving fitness, decreasing decubitus, re-training muscles, re-learning functional tasks, enhancing neuroplasticity (beneficially changing the structure in the brain/spine), treatment of drop foot, increasing walking speed, fighting muscle atrophy, maintaining peripheral nerve function, maintaining the functioning of the brain, improving blood flow, improving the bone mineral density, management of the urinary tract, …

In short, electrical stimulation under the supervision of experts appears to be a safe medical method without known negative side effects. It can be used to remedy many consequences of motor impairments and increase the quality of life.

Electrical stimulation for fighting pain

As you’ve just read, the electric signals can be used for many things. One of the things for which this electricity can be used is to fight pain. For fighting pain, the electricity can be applied to the spinal cord (epidural stimulation). However, the stimulation can also be applied to the nerves or muscles to fight pain. In this case, it is often called Transcutaneous Electrical Nerve Stimulation (TENS). The links can offer you more information about these therapies.

Functional Electrical stimulation (FES): motor relearning

FES means that the electrical stimulation is being used in order to execute functional movements. This way, it is possible to enhance functional recovery: The recovery of voluntarily making movements. When an electrical signal is sent to a nerve, it does not only go towards the muscle. The signal proceeds into two directions: towards the muscles and, through sensory nerves back towards the central nervous system, including the brains. Thanks to this, it is possible to ‘synchronize’ the moment of the muscle movement with the moment at which the sensory signal reaches the brain. This can be very useful for people who do not, or insufficiently, have the ability to voluntarily initiate movements. When this is used as a training, it may strengthen the path from muscle to brain, so that people can re-learn the ability to initiate movements and activate their muscles again. Of course, the functional effects differ per injury, as the problem may sometimes concern the nerve paths, and sometimes the brain or the spinal cord.

Electrical stimulation in combination with EMG-signals

This is another way for working towards recovery of that tract between muscles and brains. Multiple electrical stimulators exist that can measure so-called EMG-signals. EMG is short for Electromyography. This is a signal that comes up when muscles are activated. After having a stroke or spinal cord injury, for example, certain muscles can only limitedly be activated. Let alone the muscles that cannot be activated at all, of course. The EMG-signals of these half-functioning muscles can be measured. Because of this, electrical stimulation can become activated at the moment someone tries to make a movement. In this way, the electrical stimulation is synchronised with the activation from the brain. This could offer training possibilities to re-enable movement that were previously impossible. The next video offers a (slightly romantic) image of this.

The above video is commercial, but does offer a proper image of the utility of EMG-triggered electrical stimulation.

Electrical stimulation of the spinal cord

Electrical stimulation is not just applied to muscles. Another treatment for making the muscles of people with spinal cord injuries move again is epidural stimulation. Epidural stimulation is a form of stimulation of the spinal cord. You can read more about it by clicking the link.

 

Support for the facts mentioned in the text includes the following studies:

(1): Bersch I, Tesini S, Bersch U & Frotzler A (2015). Functional Electrical Stimulation in Spinal Cord Injury: Clinical Evidence Versus Daily Practice, Artificial Organs, 39 (10): 849 -54.

(2): Bosques G, Martin R, McGee L, Sadowsky C (2016) Does therapeutic electrical stimulation improve function in children with disabilities? A comprehensive literature review. Journal of Pediatric Rehabilitation Medicine,9 (2): 83-99.

(3): Chen JC, Shaw FZ (2014) progress in sensorimotor rehabilitative physical therapy programs for stroke patients. World journal of clinical cases, 3(8): 316-326.

(4): Ho CL, Holt KG, Saltzman E, Wagenaar RC (2006) Functional Electrical Stimulation Changes Dynamic Resources in Children With Spastic Cerebral Palsy physical therapy, 86 (7): 987 – 1000.

(5): Karabay İ, Dogan A, Arslan MD, Dost G, Ozgirgin N (2012) Effects of functional electrical stimulation on trunk control in children with diplegic cerebral palsy. Disability and Rehabilitation, 34 (11): 965-970.

The information concerning electrical stimulation mentioned on this website will be furtherly elaborated soon!

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