Effects of pacing when using material handling manipulators

Common manipulator-assisted materials handling tasks were performed in a la boratory simulation at self-selected and faster (paced) speeds. The effects of pacing on peak hand forces, torso kinematics, spine moments-and forces, and muscle antagonism were determined, along with any influences of severa l task variables on these effects. The faster trials were performed 20% mor e rapidly than the self-paced trials. It was found that (a) achieving this level of performance required similar to 10% higher hand forces and 5%-10% higher torso moments, (b) consistent torso postures and motions were used f or both speed conditions, and (c) the faster trials resulted in similar to 10% higher spine forces and similar to 15% higher levels of lumbar muscle a ntagonism. On whole, these results suggest a higher risk of musculoskeletal injury associated with performance of object transfers at faster than self -selected speeds with and without a manipulator. Further analysis provided evidence that the use of manipulators involves higher levels of motor coord ination than do manual tasks. Several implications regarding the use of mat erial handling manipulators in paced operations are discussed. Results from this investigation can be used in the design, evaluation, and selection of material handling manipulators.