Strength demands of line handlers on the Panama canal

Vessels transiting the Panama Canal are guided through the locks using locomotives attached by means of towlines (made of wire rope), which are fastened to bitts on the deck by line handlers. The latter activity requires high pulling strength demands and is thought to be a cause of the high incidence of low back disorders in these workers. At the invitation of the Panama Canal Commission, NIOSH researchers evaluated the strength demands of line handlers and the strength capabilities of a line handling crew. Strength demands measured during a transit indicated high pulling force demands for attaching ropes to the bow and stern bitts (> 1000 N), but lower force requirements for midships bitts (< 400 N). Tests of pulling strength capabilities of a line handling crew suggest that at least 4-5 line handlers are needed to perform the most demanding tasks. When pulling upwards or downwards on a rope in a team effort, ordering the crew according to stature appears important. Simulation of slippery deck conditions resulted in a 13% decrease in team pulling strength. Though the short duration of the study prevented an extensive evaluation, the data obtained provides insight into the design aspects of occupations where team-pulling activities are required.