A Finite Element Model for Describing the Effect of Muscle Shortening on Surface EMG

A finite-element model for the generation of single fiber action potentials in a muscle undergoing various degrees of fiber shortening is developed. The muscle is assumed fusiform with muscle fibers following a curvilinear path described by a Gaussian function. Different degrees of fiber shortening are simulated by changing the parameters of the fiber path and maintaining the volume of the muscle constant. The conductivity tensor is adapted to the muscle fiber orientation. In each point of the volume conductor, the conductivity of the muscle tissue in the direction of the fiber is larger than that in the transversal direction. Thus, the conductivity tensor changes point-by-point with fiber shortening, adapting to the fiber paths. An analytical derivation of the conductivity tensor is provided. The volume conductor is then studied with a finite-element approach using the analytically derived conductivity tensor. Representative simulations of single fiber action potentials with the muscle at different degrees of shortening are presented. It is shown that the geometrical changes in the muscle, which imply changes in the conductivity tensor, determine important variations in action potential shape, thus affecting its amplitude and frequency content. The model provides a new tool for interpreting surface EMG signal features with changes in muscle geometry, as it happens during dynamic contractions

Europe's Great Divide. A geo-economic-political map. LEQS Discussion Paper No. 101/2015 December 2015

It is now widely agreed that an important driver of the European economic crisis has been the faulty original design of the Monetary Union, and that substantial steps are urgently needed towards the creation of truly European fiscal institutions. The notorious stumbling block along this path is political will. By cross-referencing the results of the 2014 elections of the European Parliament with Eurobarometer opinion polls and an indicator of economic pain, we argue that Europe experiences an unresolved tension between "more Europe" and "less Europe" at the level of European peoples. Data analysis at the country level reveals a surge of what we call Europe's Great Divide, a geo-economic-political cleavage across the EU and across the EZ as well. This is more complex, and perhaps worse, than the simplistic divide between "North" and "South" or "Core" and "Periphery", and it seriously undermines support for ‘more Europe’ "from below"