Ergonomic Intervention of Reduced Reach Force and Rate Attenuates High Repetition High Force Induced Bone Osteopenia in Distal Forelimb Bones

Abstract

Using a rat model of overuse, we have shown that prolonged performance of a high repetition high force (HRHF) reaching and grasping task (12 weeks) induced significant osteopenic changes in distal forelimb bones that were attenuated by 8 weeks of ibuprofen treatment. Here, we evaluated the effectiveness of an ergonomic intervention of switching rats from a high repetition high force (HRHF) task to a reduced force and reach rate task. Trabecular structure in distal radius and ulna bones was examined in young adult rats performing one of three repetitive handle-pulling tasks for 12 wks: 1) HRHF, 2) low repetition low force (LRLF), or 3) HRHF task for 4 wks and then the LRLF task for 8 wks (HRHF-to-LRLF). Distal forelimb bones of HRHF rats showed enhanced bone resorption. In contrast, HRHF-to-LRLF rats showed no bone resorptive changes, and instead showed increased bone formation. These findings support the idea of reduced workload as an effective approach to management of work-related musculoskeletal disorders and begin to define reach rate and load level boundaries for establishing activity ranges for such interventions.