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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: Hamill pp 81-85; Cram pp 32-37, Ch 3; DeLuca website tutorial (http://www.delsys.com ),http://www.delsys.com
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Muscle structure
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The motor unit
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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
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Muscle Fiber Types
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Recruitment proceeds from smallest fibers to largest (the size principle)
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Three- component model of muscle contraction
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Length- tension relationship
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Force- Velocity relationship
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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
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The EMG signal
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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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Filtering: Effect of different cutoff frequencies on EMG
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Factors affecting the electromyogram
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Analyzing the EMG signal
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The concept of Frequency decomposition
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Converting EMG from time domain to frequency domain What is the time block, Or window over which Frequency analysis is done?
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EMG in the Frequency Domain
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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
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Timing and degree of excitation
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EMG-force relationship
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Electromechanical delay
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Windowing is a critical step in converting EMG signal from time to frequency domain
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The fatigue index From EMG – Review the Assumptions Inherent in this procedure
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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
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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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