A FSR sensor cuff to measure muscle activation during strength and gait cycle for lower limb

• Main Authors: Sobh, Khaled Nedal Mahmoud, Abd Razak, Nasrul Anuar, Abu Osman, Noor Azuan
• Format: Article
• Published: Institute of Electrical and Electronics Engineers 2022
• Subjects: R Medicine; TJ Mechanical engineering and machinery
• Online Access: http://eprints.um.edu.my/41273/
• Institution: Universiti Malaya

The assessment techniques used for people who experience muscular issues, regardless of the cause, are crucial to resolve the issue and fill the gap left by the deficiency in their muscles. The amputees' demands in their rehabilitation process are made more evident by evaluating the residual limb muscles. The time-varying muscle activity of the amputees weakens the efficiency of using these fixed positions inside the socket, which leads to a great challenge for them to continue using the prosthesis in this case. Depending on the daily motion activity or routine of the amputees, a change in the level of muscle activation may occur because every motion activity has its dynamic that depends on muscle activity. For this purpose, a new reliable cuff system using a simple, non-invasive sensor based on a force-sensitive resistor (FSR) which can measure muscle contraction, is presented in this study. The cuff system was designed by Autodesk Inventor software and used Cura for slicing functions. This design was printed by Creator-Pro 3D printer as an FDM type. The cuff includes 8 FSR sensors printed with TPU and APL for the cube. Applying FSRs on the skin senses the mechanical force exerted by the underlying contracting muscles. Regarding FSR signals and data collection and display, Datastreamer by Microsoft Excel was used for this purpose. Five male non-amputee subjects were involved in this study to do two activities (strength muscles and gait cycle). Each activity was subjected to two tests, the first conducted above the knee, while test 2 was below the knee. Rectus femoris (RF) and tibialis anterior (TA) muscles were targeted as a positioning reference for above and below the knee tests, respectively. Through the experiments, there was no complaint from the subjects about the surface of the cuff touching the skin. Still, the issue revolved around the tightness of the cuff, especially at the above-knee level for both activities. As thigh circumference, the cuff stretching efficiency was achieved over maximum stretch capability at 63 cm. After more than 50 trials with the two activities mentioned above, there was no change in the cuff dimensions either for maximum or minimum size, i.e., without stretching occurring. F1- all individuals for both activities displayed no appreciable signal variations and began with high levels of values, according to the signals data. That results from the tightness of the cuff on the limb. As a result of its site being unfavorable to any muscle activity, F2 presented poor signals in both activities for all participants. The cuff size needs to be reevaluated to prevent the problem of cuff tightness. The findings of the trials generally demonstrated the muscles' active locations and the change of activity taking place in those positions. On the other hand, the findings of the experiments also presented the inactive positions.