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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 ), . Muscle structure. The motor unit.

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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. Muscle structure

  3. The motor unit

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

  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. Force-Velocityrelationship

  10. Electromyography: The analysis of muscle electrical activity • The electromyogram • Recording the Electromyogram • Factors affecting electromyogram • Analyzing the electromyogram • Applications of electromyography

  11. The EMG signal

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

  13. Filtering: Effect of different cutoff frequencies on EMG

  14. Factors affecting the electromyogram

  15. Analyzing the EMG signal

  16. The concept of Frequency decomposition

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

  18. EMG in the Frequency Domain

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

  20. Timing and degree ofexcitation

  21. EMG-force relationship

  22. Electromechanical delay

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

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

  25. 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

  26. Further readings on Electromyography • Journal articles with specific review assignments: • Hildenbrand & Noble. (2004) J Ath Trng. Abdominal muscle activity using different exercise equipment. • Caterisano, et al (2002) J Str & Cond Res. EMG of Hip and thigh muscles during back squat. • Anders (2006) ACE FitnessMatters. EMG of gluteus maximus during various hip extension exercises. • Additional detailed tutorial on methodology (optional): • Electromyography in biomechanics. • J Appl Biomech, 19:135-163. (can be found • DeLuca, C. J. (1997) “The use of surface electromyography in biomechanics” • on delsys.com website). Click on “library”, then “tutorials”, then article title.

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