Four groups of eight lorry drivers, transporting goods on wheeled cages, as packed goods, on pallets, or as bulk cargo, were studied during a complete working day. The drivers working with bulk cargo served as a reference group. Manual materials handling and the working postures were studied by observation. The heart rate (HR) was continuously recorded and related to observed tasks. The relationship between HR and oxygen uptake during a simulation of loading and unloading and the maximal oxygen uptake (VO2 max) were measured in a laboratory for every driver. The lorry drivers worked long hours, only the group transporting wheeled cages worked less than 11 hd-1 on average. Driving made up almost half of the total working time in all groups. In general, the highest HR was found during loading and unloading. Loading and unloading of wheeled cages was done for 2 hd-1, at 50% of VO2 max. The drivers transporting packed goods and pallets loaded and unloaded for around 100 min d-1, at 48% and 35% of VO2 max respectively. When the drivers of these two groups lifted, their trunks were flexed for more than 60% of the time. The most important difference between the reference group and the other groups was that the drivers of the former rarely pushed or pulled anything. It is suggested that the required pushing and pulling forces were largely responsible for the high physical workload during loading and unloading. (A)
Abstract