title: 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 micromol l(-1)) and pyruvate (187+/-89 vs. 125+/-63 micromol 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.
authors.affiliation: Rehabilitation Medicine, Department of Clinical and Experimental Medicine, Linköping University, 581 85 Linköping, and Pain and rehabilitation Centre, University Hospital, 581 85 Linköping, Sweden DanTrials A/S, Markvangen 20, DK-2820 Gentofte, Denmark National Research Centre for the Working Environment, Copenhagen, Denmark Institute of Sports Science and Clinical Biomechanics, Campusvej 55, DK-5230 Odense M, Denmark Occupational medicine, Department of Clinical and Experimental Medicine, Linköping University, 581 85 Linköping, Sweden Plastic Surgery, Department of Clinical and Experimental Medicine, Linköping University, S-581 85 Linköping, Sweden Sports Medicine Research Unit and Copenhagen Muscle Research Center, Bispebjerg Hospital, Copenhagen, Denmark.
authors.forename: B
authors.initials: B
authors.lastname: Larsson
authors.forename: L
authors.initials: L
authors.lastname: Rosendal
authors.forename: J
authors.initials: J
authors.lastname: Kristiansen
authors.forename: G
authors.initials: G
authors.lastname: Sjøgaard
authors.forename: K
authors.initials: K
authors.lastname: Søgaard
authors.forename: B
authors.initials: B
authors.lastname: Ghafouri
authors.forename: A
authors.initials: A
authors.lastname: Abdiu
authors.forename: M
authors.initials: M
authors.lastname: Kjaer
authors.forename: B
authors.initials: B
authors.lastname: Gerdle
mesh_terms: D000328:Adult; D015415:Biomarkers / Q000032:analysis / Q000378:metabolism; D012090:Cumulative Trauma Disorders / Q000378:metabolism* / Q000503:physiopathology; D004576:Electromyography; D004734:Energy Metabolism / Q000502:physiology*; D017079:Exercise Tolerance / Q000502:physiology; D045604:Extracellular Fluid / Q000378:metabolism; D005260:Female; D005356:Fibromyalgia / Q000209:etiology / Q000378:metabolism* / Q000503:physiopathology; D006801:Humans; D006854:Hydrocortisone / Q000652:urine; D018836:Inflammation Mediators / Q000378:metabolism*; D008875:Middle Aged; D009129:Muscle Tonus / Q000502:physiology; D018482:Muscle, Skeletal / Q000378:metabolism* / Q000503:physiopathology; D009619:Nociceptors / Q000502:physiology; D009784:Occupational Diseases / Q000378:metabolism / Q000503:physiopathology; D010147:Pain Measurement; D012039:Regional Blood Flow / Q000502:physiology; D020069:Shoulder Pain / Q000209:etiology / Q000378:metabolism* / Q000503:physiopathology; D013315:Stress, Psychological / Q000150:complications / Q000378:metabolism / Q000503:physiopathology
chemical_list: D015415:Biomarkers; D018836:Inflammation Mediators; D006854:Hydrocortisone