Repetitive tasks may decrease motor performance by lessening the duration of the task and by the diminishment of fine motor skills.
A reach/grasp for food was performed by a group of rats trained to perform a repeat reaching/low force grasp task at a rate of four reaches/minute, two hours/day, three days/week for up to eight weeks. Researchers conducting the experiment noted that the number of reaches per minute lessened and task duration lengthen over an eight week period and that fine motor skill diminished. Additionally, the rats also displayed a refusal to perform the task for the work duration.
The authors felt the task was similar in action to a packing job whereby items are taken from a conveyer and placed in a packing box.
Histological examination of tissues from the anterior forelimb of the reach limb disclosed a fraying of tendon fibrils after six weeks. In all of the six- and eight-week rats, morphological changes were noted at the muscle-tendon junctions. At the cellular level, an increase in regional macrophages was discovered suggestive of a local inflammatory process.
Barbe M.F., Barr A.E., Gorzelany I., Amin M., Gaughan J.P., and Safadi F.F. “Chronic Repetitive Reaching and Grasping Results in Decreased Motor Performance and Widespread Tissue Responses in a Rat Model of MSD.” Journal of Orthopaedic Research 21: 167-176, 2003.
This article originally appeared in The Ergonomics Report™ on 2004-04-01.