Serum and tissue cytokines and chemokines increase with repetitive upper extremity tasks.
Barbe-MF; Elliott-MB; Abdelmagid-SM; Amin-M; Popoff-SN; Safadi-FF; Barr-AE
J Orthop Res 2008 Oct; 26(1):1320-1326
This study investigated changes in motor skills and tissues of the upper extremity (UE) with regard to injury and inflammatory reactions resulting from performance of a voluntary forelimb repetitive reaching and grasping task in rats. Rats reached for food at a rate of 4 reaches/min, 2 h/day, and 3 days/week for up to 8 weeks during which reach rate, task duration and movement strategies were observed. UE tissues were collected bilaterally at weekly time points of 3-8 weeks and examined for morphological changes. Serum was tested for levels of interleukin-1alpha (IL-1) protein. The macrophage-specific antibody, ED1, was used to identify infiltrating macrophages and the ED2 antibody was used to identify resident macrophages. Rats were unable to maintain baseline reach rate in weeks 5 and 6 of task performance. Alternative patterns of movement emerged. Fraying of tendon fibrils was observed after 6 weeks in the mid-forelimb. After 4 weeks, a general elevation of ED1-IR macrophages were seen in all tissues examined bilaterally including the contralateral, uninvolved forelimb and hindlimbs. Significantly more resident macrophages were seen at 6 and 8 weeks in the reach limb. At 8 weeks, serum levels of IL-1alpha increased significantly above week 0. Our results demonstrate that performance of repetitive tasks elicits motor decrements, signs of injury and a cellular and tissue responses associated with inflammation.
Laboratory-animals; Animals; Animal-studies; Injuries; Repetitive-work; Cellular-reactions; Cumulative-trauma; Cumulative-trauma-disorders; Ergonomics
Mary F. Barbe, Department of Physical Therapy, College of Health Professions, Temple University, 3307 North Broad Streeet, Philadelphia, PA 19140
Journal of Orthopaedic Research