title: Chronic repetitive reaching and grasping results in decreased motor performance and widespread tissue responses in a rat model of MSD.
abstract: 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.
authors.affiliation: Department of Physical Therapy, College of Allied Health Professions, Temple University, 3307 North Broad Street, Philadelphia, PA 19140, USA. mbarbe@temple.edu
authors.forename: Mary F
authors.initials: MF
authors.lastname: Barbe
authors.forename: Ann E
authors.initials: AE
authors.lastname: Barr
authors.forename: Irene
authors.initials: I
authors.lastname: Gorzelany
authors.forename: Mamta
authors.initials: M
authors.lastname: Amin
authors.forename: John P
authors.initials: JP
authors.lastname: Gaughan
authors.forename: Fayez F
authors.initials: FF
authors.lastname: Safadi
mesh_terms: D000818:Animals; D001522:Behavior, Animal; D012090:Cumulative Trauma Disorders / Q000276:immunology / Q000503:physiopathology*; D004195:Disease Models, Animal; D005260:Female; D018737:Hand Strength / Q000502:physiology*; D007375:Interleukin-1 / Q000097:blood; D008264:Macrophages / Q000276:immunology; D009048:Motor Skills / Q000502:physiology; D009140:Musculoskeletal Diseases / Q000276:immunology / Q000503:physiopathology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013708:Tendon Injuries / Q000276:immunology / Q000503:physiopathology; D013710:Tendons / Q000276:immunology / Q000503:physiopathology
chemical_list: D007375:Interleukin-1