Functional Electrical Stimulation - FES

Functional electrical stimulation uses short electrical impulses to induce muscular contractions artificially. The technology can be found in various neuroprostheses, aiming to restore impaired or lost body functions in individuals who have been paralysed due to an injury of the central nervous system (e.g., after an accident, stroke, or due to a neurological disorder). FES is a viable tool in clinical rehabilitation used in many applications such as heart pacing, diaphragm pacing (breathing), bladder control, hand grasping, standing, and walking. Depending on the particular application, stimulation is applied either externally via surface electrodes or internally by specially designed implants.
Further, FES allows for muscular training to counteract atrophy and improve force and endurance. In this context, it is also used outside of the purely clinical setting to perform recreational activities like cycling, rowing, or, more recently, swimming.

In situations where the nerve supply of the muscle is permanently lost (i.e., denervation), it is still possible to directly stimulate the muscular tissue. Compared to conventional nerve stimulation, this requires much higher energy delivered per stimulation pulse and, consequently, additional safety measures. Nevertheless, it is an essential part of rehabilitation that maintains muscle size and restores certain functionality, which untreated would lead to severe and degenerative processes.

Besides pure rehabilitation, FES can also be used for recreational activities such as cycling, rowing, or swimming. The artificial activation of muscles enables individuals with a spinal cord injury to regain a certain level of physical activity and mobility. Constant technological advances and an increasing understanding of the underlying physiological principles lead to novel systems adapted to and optimized for the individual use-case.