Distinct patterns of motor unit behavior during muscle spasms in spinal cord injured subjects.
نویسندگان
چکیده
Surface electromyograms (EMG) and force were recorded during repeated involuntary spasms of paralyzed triceps surae muscles of four men with chronic cervical spinal cord injury. The firing rates of 78 medial gastrocnemius (MG) motor units also were recorded intramuscularly with tungsten microelectrodes. Spasms typically involved a relatively rapid rise, then a more gradual fall in triceps surae EMG and torque. Motor unit firing rates either increased and then decreased with the spasm intensity (54%) or were relatively constant (26%), firing mainly at 2-10 Hz. The remaining units (20%) produced trains that included one or several doublets. Mean peak spasm firing rates were 18 +/- 9 Hz (mean +/- SD) for rate modulated units and 11 +/- 10 Hz for units with little or no rate modulation. Some motor units fired at rates comparable with those recorded previously during maximum voluntary contractions performed by intact subjects. Others fired at rates below the minimum usually seen when normal units are first recruited (< 6 Hz). Doublets (interspike interval < 10 ms) often repeated every 123-333 ms, or were interspersed in trains firing at low steady rates (< 11 Hz). This study shows that rate coding for many motor units appears to be similar whether descending motor input is intact or whether it has been reduced severely by spinal cord injury. In contrast, rate modulation in other units appears to depend mainly on voluntary motor commands.
منابع مشابه
University of Groningen Motor unit firing rates during spasms in thenar muscles of spinal cord injured subjects
متن کامل
RAPID COMMUNICATION Distinct Patterns of Motor Unit Behavior During Muscle Spasms in Spinal Cord Injured Subjects
Thomas, C. K. and B. H. Ross. Distinct patterns of motor unit shift. These spasms thus would seem to provide a unique behavior during muscle spasms in spinal cord injured subjects. opportunity to examine the extent of motor unit rate modulaJ. Neurophysiol. 77: 2847–2850, 1997. Surface electromyograms tion in muscles to which maximal voluntary drive fails to (EMG) and force were recorded during ...
متن کاملMotor unit firing rates during spasms in thenar muscles of spinal cord injured subjects
Involuntary contractions of paralyzed muscles (spasms) commonly disrupt daily activities and rehabilitation after human spinal cord injury (SCI). Our aim was to examine the recruitment, firing rate modulation, and derecruitment of motor units that underlie spasms of thenar muscles after cervical SCI. Intramuscular electromyographic activity (EMG), surface EMG, and force were recorded during the...
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ورودعنوان ژورنال:
- Journal of neurophysiology
دوره 77 5 شماره
صفحات -
تاریخ انتشار 1997