140 likes | 328 Views
IE 552 Mechanics of Musculoskeletal System Dr. Andris Freivalds Class #31. Nerve Conduction Waveform. Changes Over Time. Onset Latency Nerve Conduction Velocity. Limitations of Nerve Conduction. Individual variations Temperature –NCV ↓ as Temp ↓ Age effect –
E N D
IE 552 Mechanics of Musculoskeletal System Dr. Andris Freivalds Class #31 IE 552
Nerve Conduction Waveform IE 552
Changes Over Time Onset Latency Nerve Conduction Velocity IE 552
Limitations of Nerve Conduction • Individual variations • Temperature –NCV ↓ as Temp↓ • Age effect – NCV ↓ as age ↓ • BMI (gender) effect IE 552
Electromyography • Electromyography (EMG) – electrical activity in muscles • Nerve AP to motor endplate • Muscle AP and Ca++ release • Actin and myosin crossbridging • Muscle contraction and force production • A measure of: • Muscle activation • Muscle force (indirectly) • Medical disorders IE 552
EMG Instrumentation - 1 • Electrodes • Surface (noninvasive) vs. needle (invasive) • Bipolar vs. unipolar • Placement, preps, electrical impedance • Preamplifier • High input impedance • Signal-to-noise ratio IE 552
EMG Instrumentation - 2 • Amplifier • Bandwidth • Gain • Portable • Safety • Signal processor IE 552
EMG Analysis – 1Smoothed-Rectified Signal • Root-mean-squared (RMS) EMGRMS – [∫ v2(t)dt/T]½ • Smoothed-rectified • Passed through RC circuit • Integrated • Charged over a capacitor • Normalization EMGnorm = (EMGi – EMGmin)/(EMGmax – EMGmin) IE 552
Motor Unit Recruitment Rate Coding EMG-Force Relationship EMG Analysis – 2EMG Amplitude vs. Force IE 552
EMG Analysis – 3Frequency Analysis EMG Power Spectrum IE 552
Sincere Faker EMG Analysis – 3Efficiency of Electrical Activity IE 552