Analysis of the EMG signal in the frequency domain involves measurements and parameters which describe specific aspects of the frequency spectrum of the signal. Parameters of the power density spectrum may be easily used to provide useful measures of the EMG frequency spectrum.
This Application Note will explain how to extract several measures derived from the power spectrum of an EMG signal. The measures to be extracted are: Median Frequency, Mean Frequency, Peak Frequency, Mean Power, Total Power. If the EMG spectrum has a normal distribution, the Median and Mean frequencies will be identical; any deviation from normality will result in differing values for the Median and Mean frequencies.
AcqKnowledge is used to calculate these parameters after the EMG data has been collected. Methodology varies based on the version of AcqKnowledge that is used.
Automated Scoring—Starting with AcqKnowledge 4.0 for Windows or 3.9.2 for Mac the software can extract the measurements in an automated fashion.
Case A: Extracting measurements from a single contraction
Case B: Extracting measurements from multiple contractions
Manual Scoring is required when older versions of AcqKnowledge are used.