title: Increase in muscle nociceptive substances and anaerobic metabolism in patients with trapezius myalgia: microdialysis in rest and during exercise.
abstract: 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+/-1mm), muscle 5-HT higher (22.9+/-6.7 vs. 3.8+/-1.3 nmol/l), and glutamate higher (47+/-3 vs. 36+/-4 micromol/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 micromol/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.
authors.affiliation: National Institute of Occupational Health, Lersø Parkallé 105, DK-2100 Copenhagen, Denmark Department of Occupational and Environmental Medicine, University Hospital, Lund, Sweden Division of Rehabilitation Medicine, Department of Neuroscience and Locomotion, Faculty of Health Sciences, Linköping, Sweden Sports Medicine Research Unit and Copenhagen Muscle Research Center, Bispebjerg Hospital, Copenhagen, Denmark Pain and Occupational Medicine Center, University Hospital, Linköping, Sweden.
authors.forename: Lars
authors.initials: L
authors.lastname: Rosendal
authors.forename: Britt
authors.initials: B
authors.lastname: Larsson
authors.forename: Jesper
authors.initials: J
authors.lastname: Kristiansen
authors.forename: Michael
authors.initials: M
authors.lastname: Peolsson
authors.forename: Karen
authors.initials: K
authors.lastname: Søgaard
authors.forename: Michael
authors.initials: M
authors.lastname: Kjær
authors.forename: Jan
authors.initials: J
authors.lastname: Sørensen
authors.forename: Björn
authors.initials: B
authors.lastname: Gerdle
mesh_terms: D003401:Creatine / Q000097:blood; D005260:Female; D018698:Glutamic Acid / Q000378:metabolism; D006801:Humans; D007770:L-Lactate Dehydrogenase / Q000097:blood; D019344:Lactic Acid / Q000378:metabolism; D017551:Microdialysis / Q000379:methods; D018482:Muscle, Skeletal / Q000378:metabolism / Q000473:pathology; D009784:Occupational Diseases; D010146:Pain / Q000378:metabolism* / Q000503:physiopathology; D010147:Pain Measurement; D005082:Physical Exertion / Q000502:physiology*; D019289:Pyruvic Acid / Q000378:metabolism; D012039:Regional Blood Flow / Q000502:physiology; D012146:Rest / Q000502:physiology*; D012701:Serotonin / Q000378:metabolism; D013053:Spectrophotometry; D013997:Time Factors; D014463:Ultrasonography / Q000379:methods
chemical_list: D012701:Serotonin; D019344:Lactic Acid; D018698:Glutamic Acid; D019289:Pyruvic Acid; D007770:L-Lactate Dehydrogenase; D003401:Creatine