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Nonlinear Time‐Domain Analysis of EMG Activity Reveals the Timing of Motor Unit Recruitment in Diaphragm Muscle
Author(s) -
Seven Yasin Baris,
Mantilla Carlos B,
Sieck Gary C
Publication year - 2012
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.26.1_supplement.lb828
Subject(s) - motor unit , electromyography , hypercapnia , root mean square , mathematics , motor unit recruitment , medicine , physical medicine and rehabilitation , respiratory system , anatomy , physics , quantum mechanics
In previous studies, we showed that the root mean square of DIAm EMG correlates with transdiaphragmatic pressure (Pdi) reflecting force generation. We also showed that there is a shift in the power spectral density towards higher frequencies with recruitment of more fatigable fast‐twitch motor units. Recruitment of motor units leads to summation of motor unit action potentials (MUAP) causing non‐stationarity of the mean square value. Accordingly, non‐stationarity of EMG reflects motor unit recruitment. In the present study, we assessed stationarity of DIAm EMG across different ventilator and non‐ventilatory behaviors using a reverse arrangement test for 10‐ms binned mean square values. Stationarity was confirmed if 80% of the mean square calculations were within 2 standard deviations. In adult male rats, EMG recordings were obtained during eupnea, hypoxia‐hypercapnia (5% CO 2 /10% O 2 ), airway occlusion, and sneezing. At the onset of DIAm activity for each behavior, the EMG was stationary for ~75 ms. The EMG was also stationary for ~150 ms around the peak RMS for all motor behaviors. However, the period of non‐stationarity of DIAm EMG varied across motor behaviors: eupnea and hypoxia‐hypercapnia: 50 ms; airway occlusion: 240 ms; sneezing: 500 ms). Therefore, the duration of non‐stationarity of DIAm EMG increased with increasing force output; thus, reflecting the extent of motor unit recruitment.