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

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

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

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 , 2001.

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

CONVERTING MUP TO ELECTRICAL SIGNALCONVERTING MUP TO ELECTRICAL SIGNAL g; _SMU.jpg

CONVERTING MUP TO ELECTRICAL SIGNALCONVERTING MUP TO ELECTRICAL SIGNAL

ACQUIRING SIGNALACQUIRING SIGNAL Surface Electrodes – Commonly used Intramuscular Electrodes – Used for access to deep muscles – Needle and fine- wire electrodes

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

POST-PROCESSED DATAPOST-PROCESSED DATA

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

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

QUESTIONS?

REFERENCES Human Factors BME 533 “Occupational Biomechanics (4thEd.)” Don B. Chaffin, Gunnar B. J. Andersson, Bernard J. Martin Wiley Interscience, acioppo/jtcreprints/fc86.pdf