Effects of the adjustment period on psychophysically determined maximum acceptable weight of lift and the physiological cost

Abstract

The purpose of this study was to investigate the influence of adjustment periods (20, 30, 40, and 50 min) on the maximum acceptable weights of lift (MAWL) and the resulting responses (heart rate and rating of perceived exertion) on participants during lifting a container from the floor to knuckle height at various frequencies (1, 2, 4, and 6 lifts/min). A total of 6 males were recruited as the participants to perform 16 different combinations of lifting tasks. The results show that: (1) The adjustment period had a significant effect on the MAWL, and the MAWL decreased significantly as adjustment period increased. However, the effect of the adjustment period on the heart rate was not significant. In addition, the effect of the adjustment period on the rating of perceived exertion was significant. The ratings of perceived exertion (RPE) value increased as the adjustment period increased; (2) Even though the lifting frequency significantly affected the maximum acceptable weights, the lifting frequency had no significant effect on the percentage of decrease in MAWL from the 20-min adjustment period values. The participants lifted 3%, 11% and 11% less MAWL when the lifting task was performed at 30, 40, and 50 min adjustment periods, respectively. Relevance industry At the current time, there are not only extensive databases on lifting and lowering tasks, but also various multipliers and correction factors to extend the range of applicability for this data. Though many researchers have investigated the validity and reliability of the psychophysical data generated in short trials for 8-h or more of work, a very important issue concerning the effect of the adjustment period of psychophysical approach on the lifting capacity has been overlooked and not been studied.