Analysis of discomfort during a 4-hour shift in quay crane operators objectively assessed through in-chair movements

This study aims to investigate the existence of possible changes in postural strategies adopted by quay crane operators during a 4-h shift performed in a simulated environment. In particular, the analysis is carried out by analyzing the trend of in-chair-movement (ICM) as indicator of discomfort and fatigue. Using a pressure sensitive mat placed on the seat pan, average and peak body-seat pressure and trunk center-of-pressure (COP) time series were acquired and processed to calculate ICMs with two methods based on pressure changes and one which considers the COP shifts. The results show a well-defined linear trend for ICM, which was detected by all the tested approaches, with significant increases occurring after 45–60 min from the beginning of the shift. However, the method which employs COP data appears potentially more adequate to accurately identify ICM due to its relative insensitivity to external factors associated with individual’s anthropometry and body composition and presence of external vibrations. Future developments of the study will be focused on establishing the suitability of the method as non-invasive early predictor of fatigue