Lars Rosendal

Increase in muscle nociceptive substances and anaerobic metabolism in patients with trapezius myalgia: microdialysis in rest and during exercise.

&NA; Local metabolic changes are suggested to be involved in muscle pain development in humans. Nineteen women with chronic work‐related trapezius myalgia (TM) and 20 healthy female controls (CON) were studied during baseline rest, 20 min repetitive low‐force exercise, and 120 min recovery. Interstitial serotonin (5‐HT), glutamate, lactate, pyruvate, and blood flow were determined by microdialysis in the trapezius muscle. Baseline pressure pain threshold (PPT) was lower (143±18 (TM) vs. 269±17 (CON) kPa) (mean±SEM), pain intensity (visual analogue scale, VAS) higher (33±5 vs. 2±1 mm), muscle 5‐HT higher (22.9±6.7 vs. 3.8±1.3 nmol/l), and glutamate higher (47±3 vs. 36±4 μmol/l) in TM than in CON (all P<0.05), whereas muscle blood flow was similar in groups. Furthermore, muscle pyruvate was higher (180±15 vs. 135±12 μmol/l) and lactate higher (4.4±0.3 vs. 3.1±0.3 mmol/l) in TM than in CON (P<0.001). In response to exercise, VAS and glutamate increased in both TM and CON (all P<0.05). In TM only, lactate and pyruvate increased significantly (P<0.02), whereas blood flow increased to similar levels in both groups. During the initial 20 min recovery period, blood flow remained increased in TM (P<0.005) whereas it decreased to baseline levels in CON. In conclusion, patients with chronic work‐related TM have increased levels of muscle 5‐HT and glutamate that were correlated to pain intensity (r=0.55, P<0.001) and PPT (r=−0.47, P<0.001), respectively. In addition, TM was associated with increased anaerobic metabolism, whereas a normal rise in blood flow was seen with exercise. These findings indicate that peripheral nociceptive processes are active in work‐related TM.

Biochemical alterations in the trapezius muscle of patients with chronic whiplash associated disorders (WAD) – A microdialysis study

The mechanisms behind the development of chronic trapezius myalgia in patients with whiplash associated disorders (WAD) appear to involve both peripheral and central components, but the specific contribution of alterations in muscle is not clear. Female patients with WAD and involvement of trapezius (N=22) and female controls (N=20; CON) were studied during an experiment compromised of rest (baseline), 20min repetitive low‐force exercise and 120min recovery. Their interstitial concentrations of serotonin (5‐HT), glutamate, lactate, pyruvate, potassium, interleukin‐6 (IL‐6), and blood flow were determined in the trapezius muscle using a microdialysis technique. Pressure pain thresholds (PPT) over trapezius and tibialis anterior muscles were also assessed. In WAD, we found signs of generalized hypersensitivity according to PPT. The WAD group had significantly higher interstitial [IL‐6] and [5‐HT] in the trapezius than the CON. [Pyruvate] was overall significantly lower in WAD, and with lactate it showed another time‐pattern throughout the test. In the multivariate regression analysis of pain intensity [5‐HT] was the strongest regressor and positively correlated with pain intensity in WAD. In addition, blood flow, [pyruvate], and [potassium] influenced the pain intensity in a complex time dependent way. These findings may indicate that peripheral nociceptive processes are activated in WAD with generalized hypersensitivity for pressure and they are not identical with those reported in chronic work‐related trapezius myalgia, which could indicate different pain mechanisms.

Responses of algesic and metabolic substances to 8 h of repetitive manual work in myalgic human trapezius muscle

Abstract The trapezius muscle often develops pain as the result of repetitive and stressful work tasks although it is unclear to what extent this pain is due to alterations in muscle concentrations of algesic/nociceptive substances. Twenty women with chronic neck‐ and shoulder pain (TM) whose work required highly repetitive work tasks and 20 pain‐free female colleagues (CON) were studied during and after a full 8‐hour workday. We collected microdialysates from their dominant/most painful trapezius muscle; concentrations of serotonin, glutamate, lactate, pyruvate, potassium, bradykinin, and cytokines and blood flow were determined. In addition, we measured surface electromyogram, task exposure level, pain intensity, perceived mental stress, and urine‐cortisol. In connection to the clinical neck and shoulder examination, we determined pressure pain thresholds (PPTs) over the trapezius and tibialis muscles. TM had higher concentrations of glutamate (71 ± 42 vs. 36 ± 15 μmol l−1) and pyruvate (187 ± 89 vs. 125 ± 63 μmol l−1) than CON. Interstitial serotonin was higher in TM (before work: 10.6 ± 10.8 vs. 2.2 ± 1.2 nM; after work: 9.2 ± 8.3 vs. 1.5 ± 2.9 nM). The trapezius blood flow during the working day was higher in TM than in CON. TM had lower PPT and higher pain intensity throughout the working day. No differences in EMG, task exposure level, mental stress, or urine–cortisol in the groups were found. These findings support the idea that peripheral nociceptive processes are activated in occupationally active subjects, who are diagnosed with trapezius myalgia. In contrast, no sign of low blood flow or increased stress or muscle activity markers were found in TM.

Increased levels of interstitial potassium but normal levels of muscle IL-6 and LDH in patients with trapezius myalgia

Abstract The mechanisms behind the development of work‐related trapezius pain are suggested to involve both peripheral and central components, but the specific contribution of alterations in muscle nociceptive and other substances is not clear. Female patients with chronic trapezius myalgia (N=19; TM) and female controls (N=20; CON) were studied at rest, during 20 min repetitive low‐force exercise and recovery, and had their interstitial concentrations of potassium (K+), lactate dehydrogenase (LDH), interleukin‐6 (IL‐6) and collagen turnover determined in the trapezius muscle by the microdialysis technique. K+ levels were at all time points higher in TM than in CON (P<0.0001). Baseline levels of LDH and IL‐6 were similar in both groups. In response to exercise pain intensity, rated perceived exertion, and the concentrations of K+, LDH and IL‐6 increased significantly in both groups. [K+] immediately decreased to baseline levels in CON but remained elevated during the first 20 min of recovery in TM (P<0.01) whereafter it returned to baseline level. In all subjects taken together mean [K+] correlated negatively with pressure pain threshold of trapezius (P<0.001), positively with mean pain intensity VAS (P<0.001) and mean perceived exertion (P<0.001). Rises in muscle LDH and IL‐6 as well as the anabolic ratio for collagen type I was not significantly different between groups. In conclusion, patients with chronic pain in the trapezius muscle had increased levels of interstitial potassium. This finding could be causally related to myalgia or secondary to pain due to deconditioned muscle or altered muscle activity pattern.

Bradykinin and kallidin levels in the trapezius muscle in patients with work-related trapezius myalgia, in patients with whiplash associated pain, and in healthy controls - A microdialysis study of women.

Abstract The origins of chronic muscle pain development and maintenance are debated regarding the relative contributions of peripheral nociception and central pain processing. Bradykinin (BKN) and kallidin (KAL) have been suggested to be algesic kinins involved in muscle pain. This in vivo study investigates whether there were significant differences in interstitial muscle concentrations of BKN and KAL between chronic work‐related trapezius myalgia (TM), chronic whiplash associated disorders (WAD), and healthy controls (CON). These subjects were studied at rest, during a 20‐min repetitive low‐force exercise and recovery. The interstitial concentrations of BKN and KAL of trapezius were determined using the microdialysis technique. The interstitial concentration of KAL was overall significantly higher in TM than in CON. [KAL] and [BKN] increased significantly during the brief exercise in all groups. The increase in [BKN] during exercise was significantly higher in TM than in the other two groups, whereas the increase in [KAL] during exercise was highest in WAD. In chronic pain, positive correlations existed between the two kinins and the difference in pain intensity between recovery and baseline. In this in vivo study of two groups of patients with chronic pain clinically involving the trapezius muscle, we found alterations – most prominent in TM – in the interstitial concentrations of BKN and KAL. The results indicated that the two kinins were involved in aspects of hyperalgesia.

Increased interstitial concentrations of pyruvate and lactate in the trapezius muscle of patients with fibromyalgia: a microdialysis study.

OBJECTIVE The aim of this study was to compare the interstitial concentrations of pyruvate, lactate and glutamate in the trapezius muscle between patients with fibromyalgia syndrome and healthy controls. DESIGN Comparative cross-sectional study. SUBJECTS Patients with fibromyalgia (n = 19) and healthy controls (n = 19); all women. METHODS Subjects answered a questionnaire about different aspects of pain. Pressure pain thresholds over the trapezius and tibialis anterior muscles were determined. The inter-stitial concentrations of pyruvate, lactate and glutamate were determined in the resting trapezius muscle by the microdialysis technique, with samples collected every hour for 5 consecutive hours. Pain intensity was also rated. RESULTS Significantly higher interstitial concentrations of pyruvate and lactate were found in patients with fibromyalgia- syndrome. The multivariate regression analyses of group membership and pressure pain thresholds of the trapezius confirmed the importance of pyruvate and lactate. CONCLUSION Different mechanisms that may increase pyruvate and lactate in patients with fibromyalgia syndrome are discussed. Improved understanding of peripheral muscle alterations in patients with fibromyalgia syndrome could lead to mechanism-based rehabilitation.

Effect of physical training on pain sensitivity and trapezius muscle morphology.

The objective of this study was to investigate morphological and physiological characteristics of painful muscles in women with (MYA, n= 42) and without (CON, n = 20) trapezius myalgia, and assess changes in response to a 10‐week, randomized, controlled trial. MYA accomplished: (1) specific strength training (SST); (2) general fitness training (GFT); or (3) reference intervention (REF). Differences in muscle morphology could not be detected by ultrasound imaging. Significantly lower pressure pain threshold (PPT) and shoulder torque were observed for MYA, indicating pain‐related lack of full activation. After 10 weeks, increased shoulder torque and PPT of the painful trapezius were observed in SST solely. The PPT of a pain‐free reference muscle was increased in response to both SST and GFT, indicating a general effect of physical activity on pain perception. This study shows clinically relevant improvement in pain sensitivity and muscle strength capacity in response to SST. Muscle Nerve, 2010

391 BRADYKININ AND KALLIDIN LEVELS ARE INCREASED IN TRAPEZIUS MUSCLE OF PATIENTS WITH TRAPEZIUS MYALGIA BUT NOT WAD‐PATIENTS OR HEALTHY CONTROLS

Background and Aims: To adapt the Western Ontario Rotator Cuff Index (WORC) index for use in Turkey and to investigate its reliability and validity. Methods: The Turkish version of the WORC was developed according to the guidelines in the literature. Seventy-two patients with rotator cuff disease were administered the questionnaire and they were also evaluated by using the UCLA shoulder rating scale, Constant score and SF-36 to test validity. The WORC questionnaire was repeated in 35 patients after a mean interval of 2.9 days (range 2 to 7 days) to evaluate test-retest reliability. Results: Cronbach’s a was calculated as 0.92 for the total questionnaire. The intraclass correlation coefficients were very high and ranged between 0.96–0.98 for each section. There was a significant negative correlation between the Turkish version of WORC and UCLA (r = −0.598, p< 0.01), Constant score (r = −0.630, p< 0.01) and all subscales of SF-36 (p< 0.01). Conclusion: The Turkish version of the WORC index is a reliable and valid instrument for use in clinical trials in patients with rotator cuff disorders.