A Finite Element Model of the Electrically Stimulated Human Thigh: Changes due to Denervation and Training

Abstract

The complete denervation of muscles leads to changes in the muscle fibers as well as in the surrounding tissue. Concerning excitability the most important changes are reductions in fiber diameter, in muscle cross-sectional area, and in electrical conductivity of the muscle tissue. These changes can be partially reversed by intensive electrical stimulation. Evaluation of a 3D finite element axial symmetric model of the human thigh shows that the training leads to a reduction in threshold values between 17 and 51 percent, depending on the position of the fiber in the thigh. Single parameter variation clarifies the influence of each of the different factors. The electrode position was found to be most effective with the electrodes as far apart from each other as possible. Due to (i) comparatively higher changes in potentials at the distal electrode; and (ii) variations in sodium channel dynamics, lowest threshold values can be reached with a hyperpolarizing first phase of the biphasic impulse at the distal electrode. The tissue of the denervated muscle is known to be highly inhomogeneous. Simulations demonstrate that the related irregularities in the field can actually initiate fiber activation. 3D finite element simulations show the overall positive effects of FES on muscle tissue, especially an improved excitability of the muscle fibers. Furthermore the method gives an insight into the relations between potential distribution, electrode position, geometric effects, and muscle fiber activation that cannot be obtained by measurements.

A model for transcutaneous current stimulation: simulations and experiments

“…The second step describes the complex behavior of the axons' transmembrane potential (TP), which depends upon the spatiotemporal potential field along the axon [37]. Several two step models were proposed to describe TES [27,43,51]. However, these models exclusively employ static models (i.e.…”

Permanent LMN denervation of human skeletal muscle and recovery by h-b FES: management and monitoring

“…European Journal Translational Myology -Myology Reviews 1 (3): [91][92][93][94][95][96][97][98][99][100][101][102][103][104] 2010 -93 -behavior of denervated human muscle and his potential for reinnervation, establishing a dogma that continues to influence clinical managements of muscle denervation. Despite countless publications, new studies in animals and humans are enlightening several unrecognized characteristics and mechanisms of the complex processes that occur during permanent LMN denervation of muscle tissue.…”

“…European Journal Translational Myology -Myology Reviews 1 (3): [91][92][93][94][95][96][97][98][99][100][101][102][103][104] 2010 -94 -anti-C and anti-N terminals [15]. Dystrophin glycoprotein complex dysfunction was demonstrated to occur in severely atrophic muscle fibers of cancer cachexia [1].…”

“…Much of this has been excellently reviewed by Midrio [77] and Carlson [23]. In the medical literature other major issues are the neurodegenerative disorders, where partial muscle h-b FES of denervated muscle: management and monitoring European Journal Translational Myology -Myology Reviews 1 (3): [91][92][93][94][95][96][97][98][99][100][101][102][103][104] 2010 -92 -denervation and reinnervation occurs concomitantly to the muscle disease process [22,110]. The ethiopathogenic analyses of these processes are difficult since pathomechanisms of denervation ought to be distinguished from those of a progressively insufficient reinnervation [29].…”

“…Small vessels showed larger than normal size and endothelial abnormalities with thickening/duplication of basal lamina. In the two h-b FES of denervated muscle: management and monitoring European Journal Translational Myology -Myology Reviews 1 (3): [91][92][93][94][95][96][97][98][99][100][101][102][103][104] 2010 -96 -subjects, who underwent several years of h-b FES, the vascular network appeared almost normalized in ultra structural morphology and number per fiber ratio [94]. Meantime light and electron microscopy analyses showed recovery of myofiber size and ultra structure with significant reduction of fatty infiltration.…”