D9.4 - Estimating Muscular Activity of the Quadriceps Femoris Muscles by Measuring the Change in Shape
- Event
- AMA Conferences 2013
2013-05-14 - 2013-05-16
Nürnberg - Band
- Proceedings SENSOR 2013
- Chapter
- D9 - Medical Sensors
- Author(s)
- J. Hielscher, T. Meiss, R. Werthschützky - Technical University Darmstadt (Germany), J. Block - Heidelberg University Clinics (Germany)
- Pages
- 638 - 641
- DOI
- 10.5162/sensor2013/D9.4
- ISBN
- 978-3-9813484-3-9
- Price
- free
Abstract
This paper introduces a novel sensor concept for measuring muscular activity assessing the change of the skin surface curvature. The contraction of the rectus femoris muscle is expected to provide information on the user’s intention to rise from a chair. This information will be used for the control of a motorized lower limb orthosis to improve the quality of life of people suffering from muscle weakness. Electromyography is widely used for measuring muscular activity, but is affected by sweat and aging effects of the glue used to attach the electrodes. Furthermore, the necessity of glued, skin contacted electrodes reduces the ergonomic qualities. The sensor presented is designed for long-term use in an every-day environment. It consists of a thin metal stripe placed over the muscle. Deformation of the muscle during contraction causes a bending of the stripe. The generated surface strain can be
measured with strain gauges. For the application around the user’s thigh the stripe is incorporated in an elastic textile cuff. The capability of the system is evaluated in isometric exercises and sit-to-stand tasks, each compared to simultaneously recorded EMG data. Contraction and relaxation of the muscle were recognized in the signal curve. Isometric exercises revealed a higher sensitivity of the sensor for low muscular activity. During sit-to-stand tasks the signal curve showed a high similarity to the calculated knee torque. Future developments will focus on the reduction of soft tissue influence and muscle cross-talk.