Functional electrical stimulation

Under electrical stimulation is generally understood as the stimulation of the human body by externally applied electric fields.

Medical electro stimulation - therapy

In case of failure of nerve in the periphery of the body, so particularly on arms and legs, it comes to the breakdown of muscle cells supplied by the nerve paralyzed muscle. To avoid this, during a simulated treatment session with the aid of electrodes attached to a low current surges, the control of the affected nerve. This threatened the muscle is stimulated, thus moves back and not atrophied.

The muscles respond to different types of modulation of the stream differently well. In general be obtained with exponential voltage characteristics the best results.

Electrical stimulation is also used in human medicine in men with anejaculation and in veterinary medicine for the recovery of semen in breeding animals.

Hazards

The human body is very sensitive to electrical currents. Even relatively low voltages (below 40 volts) can lead to fatal injuries under unfavorable conditions ( eg strong welding and therefore good electrical conductivity). The nerves in man are also controlled by weak body's own electrical signals, which can be disturbed by the application of external electrical signals. So it may come, for example, to life-threatening cardiac fibrillation.

See also the notes to dangerous currents and voltages of the Association of Electrical Engineering ( VDE).

Functional Electrical Stimulation

As a Functional Electrical Stimulation (FES ), the electrical stimulation of a muscle is called directly or indirectly via the motor nerves to perform a muscle contraction that can be performed in two ways.

Probably the most successful and well-known use of implanted FES is the pacemaker. Depending on the damage of the heart muscle usually in the right atrium or the right ventricle (see heart) is electrically energized, too.

More FES implants: Respiratory pacemaker ( Phrenikusstimulator ), intestinal pacemaker, bladder pacemaker

Nerve stimulation

In nerve stimulation, an electric field strength is applied with sufficient strong gradient, which results in the nerve, the triggering of an action potential, which passes along the motor nerve to the motor endplate of the addressed muscle, where again, an action potential triggers, which causes subsequently contraction of the muscle.

Muscle Stimulation - electromyostimulation (EMS )

Here the muscle cell is excited directly by electrical stimuli; these stimuli have to be much larger and longer than in the stimulation of nerves. In both cases, can be done ( as the rule for training and rehabilitation) or with implanted electrodes, the functional electrical stimulation with surface electrodes on the skin. By changing the EMS stimulus frequency different areas of the muscle fiber spectrum can be different highly stressed. For frequencies between 50 and 200 Hz, the fast twitch muscle fibers are more active, while frequencies 5-10 Hz are more suitable for improving the endurance, for the slow muscle fibers are responsible. This form of stimulation is also known as EMS training and studied since at least the 1970s, both on their suitability for use with top athletes as well as for rehabilitation back. Since the stimulation does not proceed via the physiological pathway ( nervous system → muscle), but done in a direct way, the electromyostimulation is limited only makes sense to use: because it occurs combined at rest or only with simple movements, the coordination ability is not improved accordingly. Is to bear in mind that the direct muscle stimulation with low-frequency electrical stimulation is extremely painful and is therefore accepted by people little, where there is still an innervation. Therefore, medium-frequency current is far better for a direct muscle stimulation. Here working with frequencies in the 1000 Hz, which significantly reduces the sensitive strain, because the electrical resistance of the skin to an electrical stimulus is inversely proportional to frequency-dependent ( having the skin for 50 Hz a resistance of 3,000 ohms, this is 5000 Hz only around 30 ohms. ) therefore recommended for the direct muscle effect medium- frequency currents. To be particularly effective here proved to frequencies around 2,000 Hz and modulated currents. Of particular note here is the so-called modulated medium frequency (MMF ) as it is used in some therapeutic devices, but also in training systems. In training breaks that are caused for example by injury, the EMS training in any case can be a useful supplement to other forms of strength training.

Electrical stimulation by cochlear implant

Another field of application of electrical stimulation can be found in ENT. Here, the cochlear implant is used, which may allow a hearing in severe hearing loss or even deafness by direct electrical stimulation of the auditory nerve.

The electrical stimulation is carried out at different points of the scala tympani, whereby different sections of the basilar membrane and associated ganglion cells of the ear are stimulated. This leads to a tonotopic stimulation and for simulating the spatial frequency transform of the normal inner ear. Furthermore, transfer the temporal structure of the acoustic information about the stimulus rate on each electrode.

Patients with cochlear implant can not only understand language but also listen to music or phone calls to good adaptation of the speech processor and with enough practice. Especially children who were born with severe hearing loss, but need a lot of auditory training in order to learn to hear and so will also get a chance for active language.

Electrical stimulation completely denervated muscles

Currently, the only effective way of denervated muscles (permanent complete peripheral palsy ) to train, is the use of electrical stimulation with pulses of 40 - 300ms pulse width and intensities up to 250mA for direct muscle stimulation. Thus, a strength training be conducted by tetanic contractions, which lead to structural and functional results in measurable improvements.