The influence of vessel movements on the energy expenditure of fishermen in relation to activities and occupational tasks on board

BACKGROUND: Previous studies of professional fishing activities have indicated that vessel movements correlate to fishermen's energy expenditure. We have previously demonstrated that even in calm weather, the heel and pitch significantly increase the fishermen's energy expenditure, ignoring the activities carried out on board. This continuation of the study goes further by exploring the relation between the exposure to the ship's movements and the fishermen's energy expenditure during various physical activities on board.

MATERIALS AND METHODS: Four fishermen on 2 contemporary steel trawlers recorded their work activities on an hourly basis during a 4 days fishing voyage. The energy expenditure was estimated with a body monitoring system (SenseWear Pro 3) carried as an armband, placed on the right upper arm. The vessels' movements were assessed by a gyroscope placed in the wheelhouse. The additional energy expenditure relative to the energy expenditure during sleep was recorded during activities such as navigation, fishing, and machine handling and was correlated to the vessels' recorded movements (pitch/roll). Data were analysed by linear regression.

RESULTS: Roll and pitch were less than 10o for both vessels during the voyages. The fishermen's energy expenditure differed with the tasks undertaken and correlated with the vessels' movements, but for navigation and fishing the correlation was only significant in the highest - fourth quartile of - pitch/roll.

CONCLUSIONS: This study has demonstrated that vessel's movements in calm weather increase the energy expenditure during navigation, fishing, and machine handling and that the relation differs in between these activities on board and rest.