1 / 17

Quantification of E.M.G.

Quantification of E.M.G. RAW EMG. Continuously changing positive and negative deflections. How do you reduce this to one number for calculation?. A/D Skinfold Caliper Offset. 50 mm. Gain = Voltage difference / 50mm Skinfold thickness = (Voltage - Offset) / Gain. Voltage difference. Volts.

jesse-levine
Télécharger la présentation

Quantification of E.M.G.

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Quantification of E.M.G.

  2. RAW EMG Continuously changing positive and negative deflections. How do you reduce this to one number for calculation?

  3. A/D Skinfold Caliper Offset 50 mm • Gain = Voltage difference / 50mm • Skinfold thickness = (Voltage - Offset) / Gain Voltage difference Volts 0 mm Offset 0 Time

  4. RAW EMG OFFSET Signal does not oscillate around zero. Offset calculated as the average voltage

  5. Rectification After adjusting for the offset: the signal contains both positive and negative values Rectification involves the transformation of the signal into only positive deflections Average of rectified signal is used as a measure of the amount of EMG

  6. Integration Once the signal has been rectified: Integration refers to the calculation of the area under that signal waveform. This is another way of quantifying the amount of activity present during a particular period of time.

  7. Integration Value of integrated EMG is dependent upon length of time of sampling

  8. Lab Data Collection • Biceps EMG • Investigate the relationship between force and EMG • Smoothing Rectified EMG

  9. Data Collection Data Collection: 1 sec at 1000 Hz = 1000 data points Zero load - Unweighted Barbell (4 lbs) 5, 10,15, 20, 25 lbs on barbell

  10. Adjusted for offset (Subtract mean of zero load trial) • Rectified (Only positive deflections)

  11. Smoothing Rectified EMG • In the EMG custom analysis software there is a feature to smooth raw or rectified emg.

  12. Smoothing makes the pattern of change more “visible’ • Smoothing reduces amplitude • Integrated areas under the curve are similar, although slightly smaller with progressive increases in smoothing

  13. E.M.G. vs Force Relationship Calculate offset - using zero load trial Rectify five stationary trials (5 to 25lbs) Average rectified EMG Plot Ave.rect.E.M.G. and vs Force Straight line relationship?

  14. E.M.G. vs Force Relationship

More Related