Slide 1Slide 2Motion Analysis Systems - 4Electromyography (EMG) - 1Electromyography (EMG) – 2 Linearity with muscle force?Electromyography (EMG) – 3 Efficiency of electrical activityElectromyography (EMG) – 4 Frequency Analysis – Power SpectrumElectromyography (EMG) – 5 Pattern Analysis: Amplitude distributionElectromyography (EMG) – 6 Pattern Analysis: Amplitude distributionElectromyography (EMG) – 7 Measurement/InstrumentationElectromyography (EMG) – 8 SummaryStrength Measurement – 1 General Criteria for Device:Strength Measurement – 2 Whole Body Static StrengthStrength Measurement – 3 Whole Body Dynamic StrengthStrength Measurement – 4 Localized Static StrengthIntradisc Pressure Measurement -1Slide 17IE 5531IE 553 Engineering of Human WorkDr. Andris FreivaldsClass #9IE 5532IE 553 Engineering of Human WorkDr. Andris FreivaldsClass #9IE 5533Motion Analysis Systems - 43) Video-spot systemsAdvantages:1. Computerized2. No tedious calculationsDisadvantages:1. Very expensive ($50k)2. Ref pts. obscured3. Need good lighting4. Gb of dataBest for lab useIE 5534Electromyography (EMG) - 1•Summation of muscle APs•Picked up by electrodes•Raw EMG•Integrated EMG•Smoothed, rectified EMG•RMS EMGIE 5535Electromyography (EMG) – 2Linearity with muscle force?Rate Coding MU RecruitmentIE 5536Electromyography (EMG) – 3Efficiency of electrical activityIE 5537Electromyography (EMG) – 4Frequency Analysis – Power Spectrum•Fast Fourier Transform – sample 2x highest freq•Fatigue causes shift to lower frequencies–MU recruit: type I → type II–Synchronization (firing patterns)–Velocity changesNoise?IE 5538Electromyography (EMG) – 5Pattern Analysis: Amplitude distributionSteps used:A:Rectification B:Smoothing C:Calibration D:Conversion E:Rotate F:Sort into distributionIE 5539Electromyography (EMG) – 6Pattern Analysis: Amplitude distributionRecommended limits:1) Static work < 2-5% MVC2) Median < 10-14% MVC3) Peak < 50-70% MVCSample work:A) Acceptable everywhereB) Bad everywhereC) Too high static levelD) Too high peak loadsIE 55310Electromyography (EMG) – 7Measurement/Instrumentation•Electrodes: Ag-AgCl, bipolar vs. unipolar•Preamplifier: ↑ input impedance, ↑SN ratio•Amplifier: –↑common mode rejection ratio–Bandwidth: 10-1,000 Hz–Variable gain (1 V for AD input)–Fuse: current limiting–Portable, not expensiveIE 55311Electromyography (EMG) – 8Summary•Estimate•Monitor•Timing•MedicalIE 55312Strength Measurement – 1General Criteria for Device:•Provide repeatable location for force•Disperse force over contact interface•Measure force in any direction•Should accommodate individuals with various anthropometries•Must sustain high loads•Must simulate industrial jobs•Needs a readout with: peak, 3-sec average, and analog output (A-D conversion)IE 55313Strength Measurement – 2Whole Body Static Strength• Lifting: adjustable cable, load cell, readout• Push/pull: adjustable handle on rack, load cellIE 55314Strength Measurement – 3Whole Body Dynamic Strength•Isokinetic dynamometer (constant velocity)•Load cell•Standardized tests•Mini GymIE 55315Strength Measurement – 4Localized Static StrengthKey: Isolate specific muscle group/jointIE 55316Intradisc Pressure Measurement -1• Nucleus pulposus = 80% water• Pressure increases with loading• Andersson, Nachemson, Ortengren, Elfstrom, 1970sIE 55317Intradisc Pressure Measurement
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