1. ENGR 518 – Experimental TechniquesENGR 518 – Experimental Techniques Katlin LandersKatlin Landers ELECTROMYOGRAPHY

2. OUTLINE Overview of Electromyography Significance Theory How Electromyography Systems work – Converting MUP to Electrical Signal – Acquiring Signal – Post-processing Methods Common Factors Affecting EMG Summary References

3. OVERVIEW OF ELECTROMYOGRAPHYOVERVIEW OF ELECTROMYOGRAPHY Electromyography – Used to evaluate and record skeletal muscle activation – Electrical potential is detected Used in Biomechanics – Research – Medical Evaluation – Therapy http://www.amputation.research.va.gov/images/emg_testing.png

4. SIGNIFICANCE Research – Analyze muscle patterns During static and dynamic movements – Optimize athlete performance Medical Evaluation – Detect neuromuscular abnormalities Involuntary muscle twitching Muscular dystrophy Therapy – Evaluate muscle recovery post-injury or surgery – Help control movement of devices H. Hendricks, M. IJzerman, J de, Kroon, and G. Zilvold, “Functional electrical stimulation by means of the ‘Ness Handmaster Orthosis’ in chronic stroke patients: an exploratory study,” Clinical Rehabilitation, vol.15, pp.217-220, 2001.

5. THEORY Resting Membrane Potential – -70 to -90 mV Nerve Action Potential (NAP) – Releases chemical transmitter – Depolarizes muscle fibers Muscle Action Potential (MAP) – Electrical potential of muscle fiber Motor Unit Potential (MUP) – Superimposed MAP from multiple fibers

6. CONVERTING MUP TO ELECTRICAL SIGNALCONVERTING MUP TO ELECTRICAL SIGNAL http://sine.ni.com/images/products/us/040716_usb6008_m.jpg;http://smpp.northwestern.edu/bmec66/weightlifting/images/emg_electrode.jp g;http://noraxon.com/products/instruments.php3; http://www.officeclipart.com/office_clipart_images/laptop_computer_0515-0909-2120- 0444_SMU.jpg

7. CONVERTING MUP TO ELECTRICAL SIGNALCONVERTING MUP TO ELECTRICAL SIGNAL

8. ACQUIRING SIGNALACQUIRING SIGNAL Surface Electrodes – Commonly used Intramuscular Electrodes – Used for access to deep muscles – Needle and fine- wire electrodes http://www.noraxon.com/img/electrodes/dual-electrodes.jpg http://www.rehab.research.va.gov/jour/02/39/6/Knutsonf01.jpg

9. POST-PROCESSING METHODSPOST-PROCESSING METHODS Evaluate offset Rectify Data – Take the absolute value of the acquired data Low Pass Filter Data Normalize Data – With maximum EMG contraction Result is a percent of Maximum contraction

10. POST-PROCESSED DATAPOST-PROCESSED DATA

11. COMMON FACTORS AFFECTING EMGCOMMON FACTORS AFFECTING EMG Electrical Noise – Decreased Impedance Use of gel, shave hair, abrade skin – Grounding – Motion Artifact Electrode Placement – Incorrect muscle – Incorrect placement on desired muscle Correct: Belly of muscle Incorrect: muscle-tendon connection

12. SUMMARY Electromyography has a variety of uses EMG is a process which converts action potentials into electrical signals Systems used to record signals – Surface vs intramuscular – Wireless vs wired Negative aspects – Mechanical adjustments – Post-processing

13. QUESTIONS?

14. REFERENCES Human Factors BME 533 “Occupational Biomechanics (4thEd.)” Don B. Chaffin, Gunnar B. J. Andersson, Bernard J. Martin Wiley Interscience, 2006 http://www.noraxon.com/ http://psychology.uchicago.edu/people/faculty/c acioppo/jtcreprints/fc86.pdf