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Rectification of EMG in low force contractions improves detection of motor unit coherence in the beta-frequency band
journal contribution
posted on 2023-06-08, 16:07 authored by Nicholas J Ward, Simon F Farmer, Luc BerthouzeLuc Berthouze, David M HallidayRectification of surface EMG before spectral analysis is a well-established preprocessing method used in the detection of motor unit firing patterns. A number of recent studies have called into question the need for rectification before spectral analysis, pointing out that there is no supporting experimental evidence to justify rectification. We present an analysis of 190 records from 13 subjects consisting of simultaneous recordings of paired single motor units and surface EMG from the extensor digitorum longus muscle during middle finger extension against gravity (unloaded condition) and against gravity plus inertial loading (loaded condition). We directly examine the hypothesis that rectified surface EMG is a better predictor of the frequency components of motor unit synchronization than the unrectified (or raw) EMG in the beta-frequency band (15-32 Hz). We use multivariate analysis and estimate the partial coherence between the paired single units using both rectified and unrectified surface EMG as a predictor. We use a residual partial correlation measure to quantify the difference between raw and rectified EMG as predictor and analyze unloaded and loaded conditions separately. The residual correlation for the unloaded condition is 22% with raw EMG and 3.5% with rectified EMG and for the loaded condition it is 5.2% with raw EMG and 1.4% with rectified EMG. We interpret these results as strong supporting experimental evidence in favor of using the preprocessing step of surface EMG rectification before spectral analysis.
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Publication status
- Published
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- Published version
Journal
Journal of NeurophysiologyISSN
0022-3077Publisher
American Physiological SocietyExternal DOI
Issue
8Volume
110Page range
1744-1750Department affiliated with
- Informatics Publications
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- No
Peer reviewed?
- Yes
Legacy Posted Date
2013-11-06First Compliant Deposit (FCD) Date
2013-10-21Usage metrics
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