Increased neuropeptides in spinal cord with performance of a highly repetitive, forceful task are attenuated with anti‐inflammatory and ergonomic interventions

Abstract

In spite of the abundant epidemiological evidence linking exposure to repetitive and/or forceful motion with repetitive strain injuries, effective interventions are still lacking. This study examined the effectiveness of 2 interventions (ergonomic modification and ibuprofen) in reducing nociceptive neuropeptides and inflammation after a highly repetitive, forceful reaching/grasping (HRHF) task. Rats were randomly assigned to 4 groups (ergonomic intervention, medicated, HRHF, or controls; 5–8/group). Controls learned, but did not perform the regimen. HRHF rats reach/grasp every 15 s at 70% of max grip strength (2hr/d, 3d/wk, 6–12 wks). Ergonomic rats performed the HRHF task for 4 wks, then transfer to a low repetition‐negligible force (LRNF) task (reach/grasp every 30 s, 20% of max). Medicated rats receive oral ibuprofen after HRHF task wk 4 and continued the task. Motor function was monitored weekly. Immunochemistry was used to analyze serum cytokines, nerve macrophages, and spinal Substance P (SP) and Neurokinin‐1 (NK‐1). In serum, ibuprofen reduced IL‐1a, interferon‐gamma, MIP2 and MIP3a, while ergonomic intervention reduced IL‐1a and MIP2. Nerve macrophages and spinal SP and NK‐1 expression were reduced by both interventions. These data suggest that a lowered work demand is as effective as ibuprofen in reducing inflammation and neuropeptides induced by repetitive, forceful tasks. NIAMS‐AEBarr