We’ve come a long way since 1780 when Luigi Galvani first made the legs of a dead frog hop using an electric shock. Nowadays electrical stimulation uses are many and varied, from localised pain relief to assisting in the delivery of medications.
However, concerning those with neurological conditions, one area is attracting the most attention,
Functional Electrical Stimulation (FES).
Every movement we make begins with the brain. Let’s say you wanted to scratch an itch on your nose right now, a series of actions need to happen in the background beforehand.
First, sensory information from the skin on your nose travels to the brain. Consciously or not you
accept the mission to remove that itch. The brain dispatches an electrical signal which travels down the brain stem, onto the spinal cord where it meets its contact, the motor neuron, on the 5th vertebrae of the cervical spine. Quick as flicking a light switch the motor neuron takes that message from the spine to the belly of the bicep where it covertly recruits just enough muscle fibres as necessary to pull on your radius bone, bringing your hand to your face.
Meanwhile, a second objective is simultaneously carried out to recruit muscle fibres on your triceps, just enough to ensure you don’t overshoot and end up picking your nose by accident.
Sensory information again relays to the brain that the itch has been terminated, and with the mission accomplished another message is sent to the muscles to stand down.
If there is that much involved in simply scratching your nose, just imagine the complexity of
something like walking.
The nervous system is an electrical superhighway of information starting at the brain and travelling to and from every other part of the body. If any part of this pathway is disturbed or broken, like in a spinal cord injury or stroke, information crossing that point is either impeded, or stopped altogether. Consequently, that command or movement cannot take place.
The purpose of FES is to jump in beneath that disruption and replicate the electrical signal coming from the brain, allowing the muscle to forcefully contract, resulting in meaningful movement.
With this intervention an individual with paraplegia could start cycling training with the assistance of an FES unit. Once electrodes are attached to the quadriceps and hamstrings of both legs, the unit can cause the muscles to contract and relax in sequence, facilitate the cycling movement.
That’s great, so what?
Well, once appropriately set up, the applications of FES are limited only by you and your therapist’s imagination.
For example, the first commercially available FES device treated foot drop in stroke patients. A switch on the heel of the patient’s shoe would activate an electrode near their shin, stimulating their peroneal nerve, which in turn lifted the front of their foot. This simple application reduced tripping, increased safety, and improved the patient’s walking pattern.
FES could be applied to generate a reach a grasp pattern to a stroke affected arm to assist in a self-feeding goal. Stimulation could be used to augment a patient’s own function, such as assisting the core in rolling. If timing or strength is lacking, then FES can assist, like initiating standing or coordinating walking. Or it can be used to provide practice where there is no active movement and give the muscle of your choice a real thorough workout.
When properly implemented with a properly qualified therapist, this technology can be a valuable contribution to any training regime. Though it is an area of continue research and development, especially in the realm of neuroplasticity and the restoration of limb function, FES has come a long way and has become standard practice in many clinical settings.
If only Galvani’s frogs were alive to see it.
References:
Frotzler A, Coupaud S, Perret C, Kakebeeke T, Hunt K, Eser P.Effect of detraining on bone and muscle tissue in subjects with chronic spinal cord injury after a period of electrically-stimulated cycling: a small cohort study. J Rehabil Med. 2009;41: 282-285
Griffin L, Decker M, Hwang J, et al. Functional electrical stimulation cycling improves body composition, metabolic and neural factors in persons with spinal cord injury. J Electromyogr Kinesiol. 2009;19: 614-622
Martin, R., Sadowsky, C., Obst, K., Meyer, B., & McDonald, J. (2012). Functional Electrical Stimulation in Spinal Cord Injury: From Theory to Practice. Topics In Spinal Cord Injury Rehabilitation, 18(1), 28-33. doi: 10.1310/sci1801-28
