Chronic repetitive reaching and grasping results in decreased motor performance and widespread tissue responses in a rat model of MSD

J Orthop Res. 2003 Jan;21(1):167-76. doi: 10.1016/S0736-0266(02)00086-4.


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.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Behavior, Animal
  • Cumulative Trauma Disorders / immunology
  • Cumulative Trauma Disorders / physiopathology*
  • Disease Models, Animal
  • Female
  • Hand Strength / physiology*
  • Interleukin-1 / blood
  • Macrophages / immunology
  • Motor Skills / physiology
  • Musculoskeletal Diseases / immunology
  • Musculoskeletal Diseases / physiopathology*
  • Rats
  • Rats, Sprague-Dawley
  • Tendon Injuries / immunology
  • Tendon Injuries / physiopathology
  • Tendons / immunology
  • Tendons / physiopathology


  • Interleukin-1