Conception of a Phantom in Agar-Agar Gel with the Same Bio-Impedance Properties as Human Quadriceps.

The physiology of the patient can be reflected by various data. Serious games, using an intelligent combination, could be based on this data to adjust to the specificities of the patient. Rehabilitation would therefore be personalized to the patient. This smart suit would use dry electrodes in order to be easily usable. Before performing dry electrode validation tests on a population, it is necessary to perform preliminary tests on a phantom. Agar-Agar (AA) gel, combined with NaCl and graphite which directly impact the resistivity and reactance values of the phantom, are generally used. Depending on the part of the body simulated by the phantom, it is necessary to adapt the concentrations of NaCl and graphite in order to obtain values of physiological reactance and resistance. The anisotropy of a muscle must also be considered. Different concentrations of NaCl and graphite have been tested in order to present charts linking the concentrations to the resistance and reactance values of the AA phantom. Electrical properties similar to those of human quadriceps are achieved at a concentration of 7 g/L of NaCl and 60 g/L of graphite. These values can be used as a conversion table to develop an AA phantom with electrical properties similar to different muscles. Furthermore, an AA phantom has an anisotropy of 0° and 90°. This anisotropy corresponds to a human quadriceps, where 0° is the direction of the muscle fiber. This will allow us to study and characterize the behavior of the electrodes on an anisotropic model. Thus it can be used as a first test phase for dry electrodes in order to propose the most suitable conditions for a connected garment application.

A reproducibility study on musculotendinous stiffness quantification, using a new transportable ankle ergometer device.

The use of biomechanical methods to quantify functional/physiological parameters in malnourished humans can provide new insights into the understanding of effects of malnutrition on human muscles. Therefore, a transportable ankle ergometer device was developed, which allows the quantification of mechanical properties of the human plantarflexor muscles in field experiments. More precisely, the ergometer quantifies isometric force in static conditions and musculotendinous stiffness in dynamic conditions. This latter parameter is obtained by the quick-release technique. The aim of the study was first to conduct a reproducibility study on musculotendinous stiffness. Seven healthy subjects were tested three times in alternate days. The results showed the well-known linear relationship between musculotendinous stiffness and torque, where the slope was used as a stiffness index (SI(MT)). Individual regression line comparison indicated that SI(MT) values were not significantly different between the three repeated measurements (P>0.05). Mean coefficient of variation was 4.5+/-1.0%. The individual SI(MT) data were within the range of those reported in the literature. The reproducibility study showed that the quantification of musculotendinous stiffness by means of the quick-release technique is a reliable method, using a transportable ankle ergometer device.