This study examined how container width, the presence or absence of container handles, and different rates and distances of load carriage influenced the maximum acceptable weight carried by well-conditioned males for one hour. After training, ten male subjects performed a manual materials carriage task that required subjects to pick up the load, turn, carry the load, put the load down, then return to the starting point. Conditions examined were container width, from 15ยท2 cm to 56 cm; rate of carriage, from one carry every 12 seconds to one carry every 60 seconds; and distance of carriage from 1 metre to 6 metres. All conditions were performed using containers with and without handles. The psychophysical method of load adjustment was used to determine the maximum acceptable weight carried in each condition. It was found that the use of container handles leads to subjects carrying a significantly lower maximum acceptable weight than was carried when containers did not have handles. It was suggested that this was due to the combined task studied and to the design of the container handles. There were significant reductions in the maximum acceptable weight carried with increases in container width, rate of carriage and distance of carriage. It was concluded that if predictions of the maximum weight that can be carried are made from data that are based on tasks performed with a single container width and using containers with handles, then significant errors in prediction may result when the actual containers used have different features.
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