Voluntary hyperventilation changes recruitment order of parasternal intercostal motor units

1987 ◽  
Vol 62 (1) ◽  
pp. 187-193 ◽  
Author(s):  
T. W. Watson ◽  
W. A. Whitelaw
Keyword(s):  
Human Subjects ◽  
Motor Units ◽  
Quiet Breathing ◽  
Rib Cage ◽  
Voluntary Hyperventilation ◽  
Single Motor ◽  
Intercostal Muscles ◽  
Single Motor Units ◽  
Normal Human ◽  
Recruitment Order

The order of recruitment of single-motor units in parasternal intercostal muscles during inspiration was studied in normal human subjects during quiet breathing and voluntary hyperventilation. Electromyograms were recorded from the second and third intercostal spaces by means of bipolar fine wire electrodes. Flow at the mouth, volume, end-expired CO2, and rib cage and abdominal anterior-posterior diameters were monitored. Single-motor units were identified using criteria of amplitude and shape, and the time of first appearance of each unit in each inspiration was noted. Hyperventilation was performed with visual feedback of the display of rib cage and abdomen excursions, keeping the ratio of rib cage to abdominal expansion. Subjects were normocapnic in quiet breathing and developed hypocapnia during hyperventilation. Recruitment order was stable in quiet breathing, but in some cases was altered during voluntary hyperventilation. Some low threshold units that fired early in the breath in quiet breathing fired earlier at the beginning of a period of voluntary hyperventilation but progressively later in the breath as hyperventilation went on, whereas later firing units moved progressively toward the early part of inspiration. This suggests that different groups of motoneurons in the pool supplying parasternal intercostal muscles receive different patterns of synaptic input.

Change in recruitment order of motor units in human parasternal intercostal muscles with sleep state

1993 ◽  
Vol 74 (6) ◽  
pp. 2718-2723 ◽  
Author(s):  
W. A. Whitelaw ◽  
K. P. Rimmer ◽  
H. S. Sun
Keyword(s):  
Sleep Stage ◽  
Human Subjects ◽  
Motor Units ◽  
Excitatory Input ◽  
Sleep State ◽  
Intercostal Muscles ◽  
Intramuscular Electrodes ◽  
Normal Human ◽  
Low Threshold ◽  
Recruitment Order

Recruitment order of individual motor units in the early part of inspiration in parasternal intercostal muscles was observed in normal human subjects during wakefulness and non-rapid-eye-movement sleep. Electromyograms from bipolar fine wire intramuscular electrodes were recorded while the subjects lay supine in a sleep laboratory, and sleep stage was determined by polysomnography. From wakefulness to sleep there were numerous examples of shifts in order of recruitment among the low threshold units of early inspiration. There were corresponding shifts in the order of derecruitment of these units. Analysis of frequency of firing of units also suggested that the levels of excitatory input to one unit of a pair could be altered relative to the level of input of the other one. The data imply that there are at least minor differences in distribution of excitatory inputs from various sources among motoneurons of this muscle pool.

Behavior of motor units in human biceps brachii during a submaximal fatiguing contraction

1994 ◽  
Vol 76 (6) ◽  
pp. 2411-2419 ◽  
Author(s):  
S. J. Garland ◽  
R. M. Enoka ◽  
L. P. Serrano ◽  
G. A. Robinson
Keyword(s):  
Motor Unit ◽  
Biceps Brachii ◽  
Discharge Rate ◽  
Human Subjects ◽  
Absolute Threshold ◽  
Motor Units ◽  
Single Motor ◽  
Threshold Force ◽  
Single Motor Units ◽  
Discharge Rates

The activity of 50 single motor units was recorded in the biceps brachii muscle of human subjects while they performed submaximal isometric elbow flexion contractions that were sustained to induce fatigue. The purposes of this study were to examine the influence of fatigue on motor unit threshold force and to determine the relationship between the threshold force of recruitment and the initial interimpulse interval on the discharge rates of single motor units during a fatiguing contraction. The discharge rate of most motor units that were active from the beginning of the contraction declined during the fatiguing contraction, whereas the discharge rates of most newly recruited units were either constant or increased slightly. The absolute threshold forces of recruitment and derecruitment decreased, and the variability of interimpulse intervals increased after the fatigue task. The change in motor unit discharge rate during the fatigue task was related to the initial rate, but the direction of the change in discharge rate could not be predicted from the threshold force of recruitment or the variability in the interimpulse intervals. The discharge rate of most motor units declined despite an increase in the excitatory drive to the motoneuron pool during the fatigue task.

Single motor unit activity in the diaphragm of cat during pressure breathing

1981 ◽  
Vol 50 (2) ◽  
pp. 348-357 ◽  
Author(s):  
B. Bishop ◽  
S. Settle ◽  
J. Hirsch
Keyword(s):  
Motor Unit ◽  
Negative Pressure ◽  
Motor Units ◽  
Positive Pressure ◽  
Quiet Breathing ◽  
Single Motor Unit ◽  
Single Motor ◽  
Single Motor Units ◽  
Negative Pressure Breathing ◽  
Phrenic Motoneuron

In this study we analyzed the breath-by-breath activity of single motor units in the diaphragm slip of allobarbital-anesthetized cats during quiet breathing and during continuous positive- and negative-pressure breathing. Our objective was to determine whether single motor units, on the basis of their activities, can be separated into discrete subpopulations or whether they fall on a continuum analogous to that of motor units of hindlimb muscles. The firing profiles of each unit were characterized for each pressure level by the onset and peak firing frequencies, onset latency, duration of firing, number of impulses per breath, and minimal frequency, when appropriate. Units with shorter onset latencies had higher peak frequencies, longer firing durations, and increased firing frequencies than did units with longer onset latencies. These comparative relationships persisted even though the activity of every motor unit was altered during pressure breathing. During positive-pressure breathing onset latencies were lengthened, and durations of firing were shortened with little change in onset or peak frequencies. Late units might be silenced. During negative-pressure breathing onset latencies were shortened, and durations of firing were lengthened, sufficiently in some cases to fill the expiratory pause. In addition, previously inactive units were recruited late in inspiration for short, relatively high frequency bursts during inspiration. The results support the concept that the phrenic motoneuron pool is comprised of three discrete subpopulations.

Human Genioglossus Single Motor Units Discharge Properties In Quiet Breathing, CO2 And CPAP.

2010 ◽  
Author(s):  
Julian P. Saboisky ◽  
Danny J. Eckert ◽  
Amy S. Jordan ◽  
Erin Kelly ◽  
John Trinder ◽  
...  
Keyword(s):  
Motor Units ◽  
Quiet Breathing ◽  
Single Motor ◽  
Single Motor Units

Activation of the parasternal intercostals during breathing efforts in human subjects

1982 ◽  
Vol 52 (3) ◽  
pp. 524-529 ◽  
Author(s):  
A. De Troyer ◽  
M. G. Sampson
Keyword(s):  
Human Subjects ◽  
Normal Subjects ◽  
Emg Activity ◽  
Tidal Breathing ◽  
Quiet Breathing ◽  
Rib Cage ◽  
Intercostal Muscles ◽  
Breathing Maneuver ◽  
Inspiratory Activity

We have tested the possibility that the electromyographic (EMG) activity present in the parasternal intercostal muscles during quiet inspiration was reflexive, rather than agonistic, in nature. Using concentric needle electrodes we measured parasternal EMG activity in four normal subjects during various inspiratory maneuvers. We found that 1) phasic inspiratory activity was invariably present in the parasternal intercostals during quiet breathing, 2) the parasternal EMG activity was generally increased during attempts to perform the tidal breathing maneuver with the diaphragm alone, 3) parasternal EMG activity was markedly decreased or suppressed in the presence of rib cage distortion during diaphragmatic isovolume maneuvers, and 4) that EMG activity could not be voluntarily suppressed during breathing unless the inspired volume was trivial. We conclude that the parasternal EMG activity detected during quiet inspiration in the normal subjects depends on a central involuntary mechanism and is not related to activation of intercostal mechanoreceptors.

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