To examine the distribution of stress-induced upper-body pain in fibromyalgia patients, and the possible association of pain with electromyographic activity in muscles near the sites of pain development.
Fifteen fibromyalgia patients and 15 pain-free subjects were exposed to low-level mental strain over a one-hour period. EMG was recorded from frontalis, temporalis, trapezius, and splenius capitis. Pain in the corresponding locations was recorded before the test, every 10 minutes during the test, and the 30-minute posttest period.
The fibromyalgia patients developed pain during the test in all the above body locations. Pain development in all locations associated with trapezius EMG activity, but not with EMG activity in underlying muscles for forehead, temples, and neck.
Stress-induced pain in fibromyalgia patients is not generally caused by muscle activity. The trapezius EMG response may be part of a general stress response that cause pain independently of motor activity in muscles.
"Chronic stress is a risk factor for both somatic outcomes, such as hypertension , , , coronary heart disease , peptic ulcers , ,  and asthma , and mental health outcomes including chronic ‘benign’ pain , , anxiety , , , PTSD , , depression ,  and burn-out , . In addition, work-related exposures such as repetitive work or mental stress during work, increase the risk for stress-related pain , , , , , , . "
[Show abstract][Hide abstract] ABSTRACT: Experience of stress may lead to increased electromyography (EMG) activity in specific muscles compared to a non-stressful situation. The main aim of this study was to develop and validate a stress-EMG paradigm in which a single uncontrollable and unpredictable nociceptive stimulus was presented. EMG activity of the trapezius muscles was the response of interest. In addition to linear time effects, non-linear EMG time courses were also examined. Taking into account the hierarchical structure of the dataset, a multilevel random regression model was applied. The stress paradigm, executed in N = 70 subjects, consisted of a 3-minute baseline measurement, a 3-minute pre-stimulus stress period and a 2-minute post-stimulus phase. Subjects were unaware of the precise moment of stimulus delivery and its intensity level. EMG activity during the entire experiment was conform a priori expectations: the pre-stimulus phase showed a significantly higher mean EMG activity level compared to the other two phases, and an immediate EMG response to the stimulus was demonstrated. In addition, the analyses revealed significant non-linear EMG time courses in all three phases. Linear and quadratic EMG time courses were significantly modified by subjective anticipatory stress level, measured just before the start of the stress task. Linking subjective anticipatory stress to EMG stress reactivity revealed that subjects with a high anticipatory stress level responded with more EMG activity during the pre-stimulus stress phase, whereas subjects with a low stress level showed an inverse effect. Results suggest that the stress paradigm presented here is a valid test to quantify individual differences in stress susceptibility. Further studies with this paradigm are required to demonstrate its potential use in mechanistic clinical studies.
PLoS ONE 04/2014; 9(4):e95215. DOI:10.1371/journal.pone.0095215 · 3.23 Impact Factor
"Stress exposure in the present study furthermore seems stronger as HCs showed markedly higher HR (ΔHR = 9 vs. 3 bpm;
) and shoulder/neck pain responses (17 vs. 3 VAS units after 30 min of stress exposure;
) than in the previous study. Indeterminate differences in test administration may cause differential sEMG responses if stress level in the test is low
[Show abstract][Hide abstract] ABSTRACT: Background
Muscle activity and pain development of fibromyalgia (FM) patients in response to mental stress show inconsistent results, when compared to healthy controls (HCs). A possible reason for the inconsistent results is the large variation in stress exposures in different studies. This study compares muscle responses of FM patients and HCs for different modes and levels of imposed stress, to elucidate features in stress exposures that distinguish stress responses of FM patients from HCs.
Upper trapezius (clavicular and acromial fibers), deltoid, and biceps surface electromyographic (sEMG) activity was recorded in FM patients (n=26) and HCs (n=25). Heart rate (HR) was recorded and used as indicator of autonomic activation. Tests included inspiratory breath holding (sympathetic activation procedure), mental stress tests (color-word test and backward counting; 28 min), instructed rest prior to stress test (30 min TV watching), and controlled arm movement. sEMG and HR was also recorded during an unrestrained evening stay at a patient hotel. The 5-min period with lowest trapezius muscle activity was determined. Pain (shoulder/neck, low back pain) and perceived tension were scored on VAS scales at the start and the end of the stress test and at bedtime.
Trapezius sEMG responses of FM patients were significantly higher than HCs during sympathetic activation, mental stress, and instructed rest, but similar during arm movement and unrestrained evening activity. HR of FM patients and HCs was similar during mental stress and in the evening, including the 5-min period with lowest trapezius activity. Muscle activity of FM patients during the stress test (with shoulder/neck pain development) and the evening stay (no pain development) was similar.
FM patients show elevated muscle activity (in particular trapezius activity) in situations with imposed stress, including sympathetic activation, and putative anticipatory stress. Muscle activity and HR were similar to HCs in instructed arm movement and in a situation approaching low-stress daily living. Pain development of FM patients during the stress test may be due to activation of several stress-associated physiological systems, and not obviously caused by muscle activity in isolation.
"To compare two pain-related conditions , such as SNP and FMS, may provide new insight into the pathogenesis and the development from regional to widespread pain conditions. Several authors have demonstrated that mental and psychosocial stress worsen pain in both conditions (Bansevicius et al., 2001; Van Houdenhove and Egle, 2004). Moreover, altered responses of the hypothalamic—pituitary—adrenal (HPA) axis have been observed in individuals with regional as well as widespread pain (McBeth et al., 2007; McFarlane, 2007; Turner-Cobb et al., 2010). "
[Show abstract][Hide abstract] ABSTRACT: Shoulder and neck pain (SNP) and fibromyalgia syndrome (FMS), two musculoskeletal conditions of unknown pathogenesis, share some common features in terms of altered neuroendocrine responses, pain and stress perception. However, the pain distribution in SNP is localized, whereas in FMS is more widespread. Because regional musculoskeletal pain may represent an intermediate stage along a continuum towards widespread musculoskeletal pain we compared the cortisol awakening response (CAR) in women with SNP with the CAR in FMS patients and healthy controls (HC) in a controlled hospital-hotel setting. The aim of the study was to investigate whether SNP is related to a deviant regulation of the hypothalamic-pituitary-adrenal (HPA) axis. Eighteen women with SNP, 29 female FMS patients, and 27 female HC participated in the study. Cortisol samples were collected upon awakening, 30 and 60 min later. Questionnaires measuring pain levels, sleeping problems, perceived stress, and psychological characteristics were administered to the participants. Compared with HC, women with SNP had a tendency towards higher cortisol levels, whereas FMS had lower cortisol levels. Adjustment for potential confounders did not influence the results. Women with SNP and FMS patients reported more health complaints, pain, and perceived stress than the HC, but women with SNP were less affected than the FMS patients. Women with SNP showed a tendency towards an elevated HPA axis activity compared with HC. The current findings may indicate that the hypercortisolism in regional musculoskeletal pain represent an intermediate stage towards the development of a hypocortisolism in widespread musculoskeletal pain.
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