Real-Time Monitoring for Knee Extensor Muscle Training With Flexible Sensors

This study constructed a system for real-time monitoring of knee extensor muscle training motion with flexible sensors. Knee extensor muscle is classified to three levels according to their skin stretch and corresponding change in electrical resistance measured by flexible sensors. The area with the largest skin stretch corresponds to the sensor location that measures the largest change in resistance. Results show that the major training sites of standard knee exercise: the rectus femoris (RF), vastus medialis (VM), and vastus lateralis (VL). In addition, the flexible sensors in the proposed system can not only be used for the standard 24 repetitions of knee extensor muscle training but also exhibit excellent reproducibility for 40 repetitions. The real-time monitoring system developed by this study has three special features: 1) determine angular velocity of knee motion; 2) determine angle of knee bending motion which has reached 30°, 60° and 90° during training; and 3) the real-time change in resistance and its relationship with time and knee angle determine whether the user is currently performing dynamic concentric or eccentric exercise or static isometric exercise.