A Study of the Effect of Work Frequency on Physical Work Capacity for Manual Materials Handling Tasks

인력물자취급시 작업빈도에 따른 생리적 작업능력의 연구

The objective of this study was to make comparison of the physical work capacities(PWCs) for three different types of tasks. For this purpose, an ergometer exercise, a treadmill exercise, and lifting activities with four different frequencies (2, 5, 8, 11 lifts/min) for the lifting range from floor to 76cm were considered. Oxygen consumption rates and heart rates were measured during the exercises and lifting activities. The PWC values for ergometer exercise test was $2562.71ml-O_2/min$ and the one for treadmill exercise was $2874.89ml-O_2/min$. The value of lifting PWC increased from $1774.07ml-O_2/min$ to $2296.76ml-O_2/min$ as the lifting frequency increased from 2 to 11 lifts/min. The ratio of the lifting PWCs to the ergometer PWC increased from 69.36% to 89.77% as the lifting frequency increased. To the treadmill PWC, the ratio increased from 62.21% to 85.24% as the lifting frequency increased. From this result, it appears that the PWCs based on the lifting tasks rather than PWCs by ergometer or treadmill exercise should be considered to determine the physiological criterion for safe weights for lifting tasks. Therefore, the physiological criteria of the NIOSH Guideline should be reexamined.