The Liberty Mutual Insurance Company's Loss Prevention Department has carried out extensive ergonomic research studies. Recently the Liberty Mutual researchers analyzed over 100 serious accidents involving workers engaged in reinforcing steel installation. In a number of previous studies of construction operations that included general concrete work, the frequency of fall injuries was so predominant that major attention was focused on that source of injury. However, it was noted in Liberty Mutual's ergonomic study that nearly half of all the injuries and dollar costs had occurred during manual handling of reinforcing steel. The injured workers were performing a variety of tasks at the time of injury, including lifting, lowering, carrying and tieing bars. The injury was generally described by the worker as severe and persistent pain in the lower back.