Injuries caused by the overstraining of muscles could be prevented by means of a system which detects muscle fatigue. Most of the equipment used to detect this is usually expensive. The question then arises whether it is possible to use a low-cost surface electromyography (sEMG) system that is able to reliably detect muscle fatigue. With this main goal, the contribution of this work is the design of a low-cost sEMG system that allows assessing when fatigue appears in a muscle. To that aim, low-cost sEMG sensors, an Arduino board and a PC were used and afterwards their validity was checked by means of an experiment with 28 volunteers. This experiment collected information from volunteers, such as their level of physical activity, and invited them to perform an isometric contraction while an sEMG signal of their quadriceps was recorded by the low-cost equipment. After a wavelet filtering of the signal, root mean square (RMS), mean absolute value (MAV) and mean frequency (MNF) were chosen as representative features to evaluate fatigue. Results show how the behaviour of these parameters across time is shown in the literature coincides with past studies (RMS and MAV increase while MNF decreases when fatigue appears). Thus, this work proves the feasibility of a low-cost system to reliably detect muscle fatigue. This system could be implemented in several fields, such as sport, ergonomics, rehabilitation or human-computer interactions.

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In this article, an educational computer application to dimension shafts is presented. Safety factors according to several classic theories can be obtained by indicating shaft dimensions and particular discontinuities, as grooves or holes. Specifying the desired security factor, necessary dimensions can be calculated. One of the advantages of the educational software developed is that text files created by it can be directly imported to the FEM software ANSYS so as to analyze stress distribution of the shaft.

This paper describes an educational computer application-MecClutch-focused on teaching the design process of mechanical clutches and their operational conditions to Mechanical Engineering students. The software is divided into three sections: (1) multimedia files, pictures, and videos, produced in order to teach the working of the mechanism, (2) theoretical information related to mechanical clutches, and (3) interactive problems that allow to design a mechanical clutch and test changes in operational conditions when varying the value of critical design parameters. This software has become a very useful tool for undergraduate Mechanical Engineering students in compliment to theoretical classes or alone, as a self-study tool.