Journal
RESPIRATORY PHYSIOLOGY & NEUROBIOLOGY
Volume 185, Issue 2, Pages 400-409Publisher
ELSEVIER
DOI: 10.1016/j.resp.2012.08.020
Keywords
Motor unit recruitment; Power spectrum; Diaphragm muscle; Stationarity; Electromyography; Neuromotor control
Categories
Funding
- National Institutes of Health [HL096750]
- Mayo Clinic
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We hypothesized that a shift in diaphragm muscle (DIAm) EMG power spectral density (PSD) to higher frequencies reflects recruitment of more fatigable fast-twitch motor units and motor unit recruitment is reflected by EMG non-stationarity. DIAm EMG was recorded in anesthetized rats during eupnea, hypoxia-hypercapnia (10% O-2-5% CO2), airway occlusion, and sneezing (maximal DIAm force). Although power in all frequency bands increased progressively across motor behaviors, PSD centroid frequency increased only during sneezing (p<0.05). The non-stationary period at the onset of EMG activity ranged from similar to 80 ms during airway occlusion to similar to 150 ms during eupnea. Within the initial non-stationary period of EMG activity 80-95% of motor units were recruited during different motor behaviors. Motor units augmented their discharge frequencies progressively beyond the non-stationary period; yet, EMG signal became stationary. In conclusion, non-stationarity of DIAm EMG reflects the period of motor unit recruitment, while a shift in the PSD towards higher frequencies reflects recruitment of more fatigable fast-twitch motor units. (C) 2012 Elsevier B.V. All rights reserved.
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