caa a22 4500 44535447X CHVBK 20180317142855.0 cr unu---uuuuu 170323e20110101xx s 000 0 eng 10.1007/s00221-010-2471-4 doi (NATIONALLICENCE)springer-10.1007/s00221-010-2471-4 Discharge rate modulation of trapezius motor units differs for voluntary contractions and instructed muscle rest [Elektronische Daten] [Jennifer Stephenson, Evangelos Christou, Katrina Maluf] This study examined discharge rate modulation at respiratory (0-0.5Hz) and beta (16-32Hz) frequencies in trapezius motor units active during voluntary contractions and during periods of instructed rest under conditions of low and high psychosocial stress. In separate sessions, single motor unit activity was recorded from the trapezius muscle of healthy women during low-intensity voluntary contractions and during periods of instructed muscle rest that followed voluntary contractions. The level of psychosocial stress during periods of instructed muscle rest was manipulated using a verbal math task combined with social evaluative threat which increased perceived anxiety, heart rate, and blood pressure (P≤0.002). Discharge rate modulation was quantified by the mean power of motor unit discharge rate profiles within frequency bands of interest. Under low stress conditions, motor units active during instructed rest had greater power at 0-0.5Hz (P=0.002) and less power at 16-32Hz (P=0.009) compared to those active during voluntary contraction. Exposure to the stressor increased the amount of motor unit activity during instructed rest (P=0.021) but did not alter the power of discharge rate modulation at 0-0.5Hz (P=0.391) or 16-32Hz (P=0.089). These results indicate that sustained motor unit activity during periods of instructed muscle rest has a lesser contribution from inputs at beta frequencies and a greater contribution from inputs at respiratory frequencies than present during low-intensity voluntary contractions. Furthermore, increases in motor unit activity when exposed to stressors during periods of instructed rest are not caused by changes in inputs at respiratory or beta frequencies. Springer-Verlag, 2010 Motor unit nationallicence Trapezius nationallicence Beta oscillation nationallicence Respiration nationallicence Stress nationallicence Electromyography nationallicence Stephenson Jennifer Department of Physical Medicine & Rehabilitation, Applied Neuromuscular Physiology Lab, Physical Therapy Program, University of Colorado Denver School of Medicine, MS C244, Education 2 South, Bldg #L28, 13121 E. 17th Ave, Room 3106, 80045, Aurora, CO, USA aut Christou Evangelos Department of Applied Physiology and Kinesiology, Neuromuscular Physiology Lab, University of Florida, 32511, Gainesville, FL, USA aut Maluf Katrina Department of Physical Medicine & Rehabilitation, Applied Neuromuscular Physiology Lab, Physical Therapy Program, University of Colorado Denver School of Medicine, MS C244, Education 2 South, Bldg #L28, 13121 E. 17th Ave, Room 3106, 80045, Aurora, CO, USA aut Experimental Brain Research Springer-Verlag 208/2(2011-01-01), 203-215 0014-4819 208:2<203 2011 208 221 https://doi.org/10.1007/s00221-010-2471-4 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/s00221-010-2471-4 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Stephenson Jennifer Department of Physical Medicine & Rehabilitation, Applied Neuromuscular Physiology Lab, Physical Therapy Program, University of Colorado Denver School of Medicine, MS C244, Education 2 South, Bldg #L28, 13121 E. 17th Ave, Room 3106, 80045, Aurora, CO, USA aut NATIONALLICENCE 700 1- Christou Evangelos Department of Applied Physiology and Kinesiology, Neuromuscular Physiology Lab, University of Florida, 32511, Gainesville, FL, USA aut NATIONALLICENCE 700 1- Maluf Katrina Department of Physical Medicine & Rehabilitation, Applied Neuromuscular Physiology Lab, Physical Therapy Program, University of Colorado Denver School of Medicine, MS C244, Education 2 South, Bldg #L28, 13121 E. 17th Ave, Room 3106, 80045, Aurora, CO, USA aut NATIONALLICENCE 773 0- Experimental Brain Research Springer-Verlag 208/2(2011-01-01), 203-215 0014-4819 208:2<203 2011 208 221 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer