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Biomechanics of Skeletal Muscle and Electroymography

Biomechanics of Skeletal Muscle and Electroymography. Biomechanics of skeletal muscle Readings: Hamill pp 76-81, 103-109 Electromyography Readings: Hamill pp 81-85; Cram pp 32-37, Ch 3; DeLuca website tutorial ( http://www.delsys.com ),.

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Biomechanics of Skeletal Muscle and Electroymography

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  1. Biomechanics of Skeletal Muscleand Electroymography • Biomechanics of skeletal muscle • Readings: Hamill pp 76-81, 103-109 • Electromyography • Readings: Hamill pp 81-85; Cram pp 32-37, Ch 3; DeLuca website tutorial (http://www.delsys.com ),

  2. Factors Influencing Production of Muscular Tension and Applied Force • Motor unit size • Muscle Fiber Type • Selective recruitment of fiber types: • SO FOG FG • Length - tension relationship • Force-velocity relationship • Angle of pull

  3. Muscle structure

  4. The motor unit

  5. Muscle Fiber Types

  6. Recruitment proceeds from smallest fibers to largest (the size principle)

  7. Three-component model of muscle contraction

  8. Length-tension relationship

  9. Angle of pull affects turning effect, or torque

  10. Length-tension, Angle of Pull Combined

  11. Force-Velocityrelationship

  12. Electromyography • The electromyogram • Recording the Electromyogram • Factors affecting electromyogram • Analyzing the electromyogram • Applications of electromyography

  13. The EMG signal

  14. Recording the electromyogram • Electrodes – • Size • Number • Placement • Signal conduction – wires or telemetry? • Signal conditioning • Amplification • Filtering • Analog to digital conversion • Integration • Frequency analysis

  15. Filtering: Effect of different cutoff frequencies on EMG

  16. Factors affecting the electromyogram

  17. Analyzing the EMG signal

  18. The concept of Frequency decomposition

  19. Converting EMG from time domain to frequency domain What is the time block, Or window over which Frequency analysis is done?

  20. EMG in the Frequency Domain

  21. Applications of electromyography • Timing of excitation • Degree of excitation • Normalization procedures • Muscle force-emg relationship • Muscle fatigue • Clinical gait analysis • Ergonomics • Limitations of EMG

  22. Timing and degree ofexcitation

  23. EMG-force relationship

  24. Electromechanical delay

  25. Windowing is a critical step in converting EMG signal from time to frequency domain

  26. The fatigue index From EMG – Review the Assumptions Inherent in this procedure

  27. Website article reading assignment • Go to website: http://www.delsys.com and download tutorial article on surface electromyography detection and recording • Be prepared to answer the following questions: • What is differential amplification? • What is common mode rejection ratio? • Where should electrodes be placed? • Where should electrodes not be placed? • How large should electrodes be? • Name 3 applications of EMG signal

  28. Further readings (optional) on Emg methodology DeLuca, C. J. (1997) The use of surface Electromyography in biomechanics. J Appl Biomech, 19:135-163. (can be found on delsys.com website) Morrish, G. (1999) Surface electromyography Methods of analysis, reliability, and main applications Physical and Rehabilitation Medicine, 11:171-205.

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