The influence of ship movements on the energy expenditure of fishermen. A study during a North Sea voyage in calm weather.

BACKGROUND Former studies of professional fishing activities have indicated that movements of a ship, in itself, may increase the energy expenditure in addition to the traditional work carried out by fishermen. We have studied the effects of exposure to the ships movement during calm weather by examining the crude relation between the ship movement and the energy expenditure of the fishermen, thus ignoringthe various tasks undertaken on board. MATERIALS AND METHODS We have recruited 4 fishermen on 2 contemporary steel trawlers who participatedduring the whole study period. Each of 4 participants recorded his activities and health conditions oncean hour in a registration scheme for 4 days. Estimations of energy expenditure were done with a bodymonitoring system (SenseWear Pro 3) carried as an armband, placed at the surface on the right upper arm. Measurements of sea movements were obtained by a gyroscope placed in the vessels wheelhouse during fishing expeditions in the North Sea off the coast of Bergen. Data were analysed by linear regression. RESULTS The exposure monitored in calm weather conditions was small for all measurements of heelingand pitch being less than 10o for both vessels. However, the fishermen's energy expenditure was influenced by these minor sea motions. Trends were seen in the individual graphs with increasing energy expenditureat higher exposures. CONCLUSIONS Our data suggest that even the heel and pitch in calm weather have an impact on the fishermen by increasing their energy consumption, but without any observation of discomfort or negative health outcomes. This study has demonstrated the feasibility of the applied methods, which should be repeated with larger samples and in rough weather.