Muscle function, electrical stimulation

While electrodes may be integrated as detectors, another possibility is to use the electrodes to stimulate muscles. Electrodes for functional electrical stimulation have been integrated into fabrics to provide actuation stimuli to muscles of the spinal cord of injured and stroke subjects in order to generate or improve lost motor function. 

The modeling and control of movements in this chapter relates to external control of muscles via so-called functional electrical stimulation. Macroscopic viscoelastic models started from the observation that the process of electrical stimulation transforms the viscoelastic material from a compliant, fluent state into the stiff, viscous state. Levin and Wyman [35] proposed a three-element model— damped and undamped elastic element in series. Hill s work [36] demonstrated that the heat transfer depends upon the type of contraction (isometric, slow contracting, etc). The model includes the force generator, damping and elastic elements. Winters [37] generalized Hill s model in a simple enhancement of the original, which... 

Here we present technical aspects of the available externally powered orthoses and prostheses that interface directly or indirectly with the human neuro-musculo-skeletal system. We elaborate here two methods for the restoration of movements in humans with paralysis functional activation of paralyzed muscles termed functional electrical stimulation (FES) or functional neuromuscular stimulation (FNS or NMS), and parallel application of FES and a mechanical orthosis called hybrid assistive system (HAS). We also describe externally controlled and powered leg and arm/hand prostheses. 

In functional electrical stimulation, the typical stimulation waveform is a train of rectangular pulses. This shape is used because of its effectiveness as well as relative ease of generation. All three parameters of a stimulation train, that is, frequency, amplitude, and pulse-width, have effect on muscle contraction. Generally, the stimulation frequency is kept as low as possible, to prevent muscle fatigue and to conserve stimulation energy. The determining factor is the muscle fusion frequency at which a smooth muscle response is obtained. This frequency varies however, it can be as low as 12-14 Hz and as high as 50 Hz. In most cases, the stimulation frequency is kept constant for a certain application. This is true both for surface as well as implanted electrodes. 

Handa, Y., Handa, T. et al.. Functional electrical stimulation (FES) systems for restoration of motor function of paralyzed muscles—Versatile systems and a portable system. Front. Med. Biol. Eng. 4 241-255,1992. 

In the area of functional electrical stimulation, skeletal muscle transfers (myoplasty) combined with electrical stimulation have been advocated to provide contractile function that augments or replaces impaired organ function (Grandjean et al., 1996). Clinical investigation of dynamic car-diomyoplasty for the treatment of heart failure and dynamic myoplasty for treatment of fecal or urinary incontinence is already under investigation. 

Functional electrical stimulation (FES) of neural tissue provides a method to restore normal function to neurologically impaired individuals. By inserting electrode inside or near nerves, it is possible to activate pathways to the brain or to muscles. Functional nerve stimulation (FNS) is often used to describe applications of electrical stimulation in the peripheral nervous system. Neural prostheses refer to applications for which electrical stimulation is used to replace a function previously lost or damaged. 

Scremin AME, Kurta L, Gentili A, et al. Increasing muscle mass in spinal cord injured persons with a functional electrical stimulation exercise program. Arch Phys Med Rehabil 1999 80 1531-1536. 

Baldi JC, Jackson RD, Moraille R, et al. Muscle atrophy is prevented in patients with acute spinal cord injury using functional electrical stimulation. Spinal Cord 1998 36 463-469. 

Marqueste T, Hug F, Decherchi P, et al. Changes in neuromuscular function after training by functional electrical stimulation. Muscle Nerve 2003 28(2) 181-188. 

The cerebral cortex is conventionally subdivided into four main regions that may be delineated by the sulci, or large clefts, termed the frontal, temporal, parietal and occipital lobes. These names are derived from the bones of the skull which overlay them. Each lobe may be further subdivided according to its cellular structure and composition. Thus Brodmarm has divided the cortex into approximately 50 discrete areas according to the specific cellular structure and function. For example, electrical stimulation of the strip of cerebral cortex in front of the central sulcus (see Figure 1.3) is responsible for motor commands to the muscles. This is termed the primary motor cortex and can be further subdivided according to which muscles are controlled in different parts of the body. 

Functional neuromuscular electrical stimulation Increased skeletal muscle strength and endurance Decreased spasticity and muscle spasms Skeletal muscle relaxants Skeletal muscle relaxants Nonselective cholinergic agonists may stimulate the neuromuscular junction -... 

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