Discharge behaviors of trapezius motor units during exposure to low and high levels of acute psychosocial stress

Stephenson, Jennifer L ORCID: https://orcid.org/0000-0001-7635-4815 and Maluf, Katrina S. 2010. Discharge behaviors of trapezius motor units during exposure to low and high levels of acute psychosocial stress. Journal of Clinical Neurophysiology 27 (1) , pp. 52-61. 10.1097/WNP.0b013e3181cb81d3

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Abstract

This study investigated the effects of acute psychosocial stress on trapezius single motor unit discharge behaviors. Twenty-one healthy women performed feedback-controlled isometric contractions under conditions of low and high psychosocial stress in the same experimental session. Psychosocial stress was manipulated using a verbal math task combined with social evaluative threat that significantly increased perceived anxiety, heart rate, and blood pressure (P < 0.001). Motor unit discharge behaviors including the threshold and discharge rate at recruitment [7.7% (5.7%) maximal voluntary isometric contraction and 7.3 pulses per second (pps) (6.8 pps), P > 0.121, N = 103] and derecruitment [6.0% (4.4%) maximal voluntary isometric contraction and 6.5 pps (4.1 pps), P > 0.223, N = 99], the mean [11.3 pps (2.3 pps), P = 0.309, N = 106] and variability [2.5 pps (0.91 pps), P = 0.958, N = 106] of discharge rate, and the proportion of motor units exhibiting double discharges (21%, P = 0.446) did not change across stress conditions. Discharge rate modulation with changes in contraction intensity was highly variable and similar across stress conditions (P > 0.308, N = 89). Rate-rate modulation of concurrently active motor units was also highly variable (r = -0.84 to 1.00, N = 75). Estimates of [DELTA]F for motor unit pairs with rate-rate modulation >=0.7 were positive and similar across stress conditions [4.7 pps (2.0 pps), P = 0.405, N = 16]. The results indicate that acute psychosocial stress does not alter trapezius motor unit discharge behaviors during a precisely controlled motor task in healthy women.

Item Type:	Article
Date Type:	Publication
Status:	Published
Schools:	Healthcare Sciences
Subjects:	R Medicine > R Medicine (General)
Uncontrolled Keywords:	Motoneuron, Anxiety, Discharge rate modulation, Persistent inward current, EMG, Muscle activation.
Publisher:	Wolters Kluwer
ISSN:	0736-0258
Last Modified:	02 Nov 2022 10:07
URI:	https://orca.cardiff.ac.uk/id/eprint/97509

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