學者在過去有關人工物料搬運的研究大多集中在抬舉作業方面，有關卸下的研究較為缺乏。此外，相對於雙手的卸下研究，單手的卸下研究更加缺乏。也因此，本研究旨在探討偶發性的卸下作業，使用心物法來檢定性別（男性與女性）和手部條件（雙手、慣用手與非慣用手）對於一次最大可承受卸下重量（MAWLo）之效應。共有29位受試者（男性20位與女性9位）參與實驗，在一次最大的條件下受試者將指節高的負重以雙手或單手卸下到地面上。研究結果證實：（1）性別對於一次最大可承受的卸下重量有顯著效應，女性卸下重量在雙手、慣用手和非慣用手分別約為男性的69%、84%和83%，整體上女性為男性的69%。（2）手部條件對於一次最大可承的受卸下重量亦有顯著效應，以雙手為最重，其次為慣用手，而以非慣用手最輕，女性在慣用手和非慣用手分別為雙手的86%和65%，男性為71%和65%，整體上則為72%和56%。（3）此外，與抬舉作業相比，國人之MAWLo與MAWL有顯著差異。（4）東西方民族在雙手與慣用手之間有顯著的差異，東方民族其價用手相對於雙手之下降百分比（40%）顯著高於西方民族下降百分比（24%）。本研究建議作業人員應盡量以雙手進行卸下作業，以降低下背的傷害。

Previous studies about the manual material handling were mostly focused on the lifting activities. However, studies related to the lowering activities are limited. In addition, comparing with lowering with both hands, studies about lowering with one hand fall far short. Therefore, this study aimed to investigate occational lowering activities, using the psychophysical approach to examine the effects of gender (male and female) and hand conditions (both hands, the dominant hand and non-dominant hand) on the maximum acceptable weight of lowering (MAWLo). A total of 29 subjects (20 men and 9 women) participated in this experiment. Under the one-time-maximum condition, participants lowered the load of knuckle height with both hands or one hand to the floor. The results confirmed that: (l) the gender had a significant effect on the maximum acceptable weight of lowering. The MAWLo of females with both hands, the dominant hand, and the non-dominant hand are 69%, 84%, and 83% of males' MAWLo, respectively. (2) Hand conditions had a significant effect on the MAWLo under the one-time-maximum condition. The MAWLo with both hands was the heaviest, followed by the dominant hand, while the MAWLo with the non-dominant hand was the lightest. For females, the MAWLo with the dominant hand and the non-dominant hands were 86% and 65% of the MAWLo with both hands, and for males, the MAWLo were 71% and 65%, respectively. Overall, the MAWLo were 72% and 56%, compared with using both hands. (3) Furthermore, compared with the lifting acti vities, there was a significant difference between MAWLo and MAWL in Taiwan. (4) There was a significant difference between Eastern and Western nations regarding to using both hands and the dominant hand. Compared to using both hands, the decreasing percentage of Eastern nations using the dominant hand (40%) was significantly higher than the Western nations (24%). This study suggested that workers should try to use both hands for the lowering activities in order to avoid the lower back injury.