Abstract
Male volunteers participated in an experiment to determine the maximum frequencies they could maintain for 2 h while lifting in the horizontal-sagittal plane using the preferred hand. The psychophysical approach was used to determine the maximum acceptable frequencies of lift for sitting and standing postures at two reach distances. Subjects were trained for six weeks. During the experiment, heart rate, ratings of perceived exertion of the back, shoulder, and arm, and the maximum acceptable frequency of lift were recorded every 15 min for 2 h. Results of this study indicate that subjects, for two hours, can maintain frequency of lifting equivalent to 51% of the maximum frequency acceptable to them for a 4-min period. Although heart rate did stabilize over the 2-h period, ratings of perceived exertion showed continuous increase. Due to training, the maximum acceptable frequency of lift increased on the average by 7.23%. Subjects accepted maximum work rate for a 4.54-kg load. Data were also collected on three females, and these were compared with data from a past study. Differences in the two studies were observed.
