title: Oxygenation and hemodynamics do not underlie early muscle fatigue for patients with work-related muscle pain.
abstract: Patients suffering from work-related muscle pain (WRMP) fatigue earlier during exercise than healthy controls. Inadequate oxygen consumption and/or inadequate blood supply can influence the ability of the muscles to withstand fatigue. However, it remains unknown if oxygenation and hemodynamics are associated with early fatigue in muscles of WRMP patients. In the present study we applied near-infrared spectroscopy (NIRS) on the extensor carpi radialis (ECR) and trapezius (TD) muscles of patients with WRMP (n = 18) and healthy controls (n = 17). Our objective was to determine if there were group differences in endurance times for a low-level contraction of 15% maximal voluntary contraction (MVC)--sustained for 12-13 min, and to see if these differences were associated with differences in muscle oxygenation and hemodynamics. At baseline, oxygen saturation (StO2%) was similar between groups for the ECR, but StO2% was significantly lower for TD for the WRMP patients (76%) compared to controls (85%) (P<0.01). Also, baseline ECR blood flow was similar in the two groups. For both muscles there were a larger number of patients, compared to controls, that did not maintain the 15% MVC for the allotted time. Consequently, the endurance times were significantly shorter for the WRMP patients than controls (medians, ECR: 347 s vs. 582 s; TD: 430 s vs. 723 s respectively). Responses in StO2% during the contractions were not significantly different between groups for either muscle, i.e. no apparent difference in oxygen consumption. Overall, we interpret our findings to indicate that the early fatigue for our WRMP patients was not associated with muscle oxygenation and hemodynamics.
authors.affiliation: Centre for Musculoskeletal Research, University of Gävle, Gävle, Sweden; Department of Community Medicine and Rehabilitation, Rehabilitation medicine, Umeå University, Umeå, Sweden.
authors.forename: Guilherme H
authors.initials: GH
authors.lastname: Elcadi
authors.affiliation: Centre for Musculoskeletal Research, University of Gävle, Gävle, Sweden; Institute of Environmental Medicine, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Mikael
authors.initials: M
authors.lastname: Forsman
authors.affiliation: Centre for Musculoskeletal Research, University of Gävle, Gävle, Sweden.
authors.forename: David M
authors.initials: DM
authors.lastname: Hallman
authors.affiliation: Department of Community Medicine and Rehabilitation, Physiotherapy, Umeå University, Umeå, Sweden.
authors.forename: Ulrika
authors.initials: U
authors.lastname: Aasa
authors.affiliation: Department of Community Medicine and Rehabilitation, Rehabilitation medicine, Umeå University, Umeå, Sweden; Department of Clinical Sciences, Professional Development, Umeå University, Umeå, Sweden.
authors.forename: Martin
authors.initials: M
authors.lastname: Fahlstrom
authors.affiliation: Centre for Musculoskeletal Research, University of Gävle, Gävle, Sweden.
authors.forename: Albert G
authors.initials: AG
authors.lastname: Crenshaw
mesh_terms: D000328:Adult; D000368:Aged; D001784:Blood Gas Analysis; D016022:Case-Control Studies; D004562:Electrocardiography; D004576:Electromyography; D017079:Exercise Tolerance; D005260:Female; D006339:Heart Rate; D006439:Hemodynamics; D006801:Humans; D007537:Isometric Contraction; D008297:Male; D008875:Middle Aged; D018763:Muscle Fatigue / Q000502:physiology*; D063806:Myalgia / Q000097:blood / Q000209:etiology* / Q000378:metabolism*; D009784:Occupational Diseases; D010101:Oxygen Consumption; D012307:Risk Factors; D055815:Young Adult
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