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Biomechanics of Skeletal Muscle and Electroymography n Biomechanics of skeletal muscle -Readings: Hamill pp 76-81, 103-109 n Electromyography -Readings:

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Presentation on theme: "Biomechanics of Skeletal Muscle and Electroymography n Biomechanics of skeletal muscle -Readings: Hamill pp 76-81, 103-109 n Electromyography -Readings:"— Presentation transcript:

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

2 Muscle structure

3 The motor unit

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

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

11 The EMG signal

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

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16 Filtering: Effect of different cutoff frequencies on EMG

17 Factors affecting the electromyogram

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19 Analyzing the EMG signal

20 The concept of Frequency decomposition

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

22 EMG in the Frequency Domain

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

24 Timing and degree of excitation

25 EMG-force relationship

26 Electromechanical delay

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

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

29 Website article reading assignment n Go to website: http://www.delsys.com and download tutorial article on “surface electromyography detection and recording”http://www.delsys.com n 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

30 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.delsys.com website


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