Abstract
A field study was conducted to evaluate the effects of lifting technique (free-style vs. straight-back, bent-knee) on male workers' performances and physiological responses. A secondary objective was to study physiological stresses to female order selectors using the free-sytle lifting technique only. Six male and six female workers performed their routine work of grocery order selection in three different warehouses while their oxygen uptake and heart rates were measured. Workers' performances were determined using the traditional work measurement techniques (time study, methods time measurement and master standard data systems) employed by the warehouses. Total cases, weight, volume, actual and allowed time for each order were also determined. Statistical analysis showed that the performance levels of the male workers (allowed time per order ★100/actual time per order) were significantly lower and oxygen uptake and heart rates were higher for the straight-back, bent-knee method as compared to the free-style lifting technique. Male workers lifted more cases, weight and volume/ min with the free-style lifting technique than with the straight-back, bent-knee method. It is concluded that the traditionally recommended straight-back, bent knee method of lifting is slower and physiologically more demanding. It is practically impossible for a substantial number of workers to meet the existing time or performance standards based on traditional work measurement techniques — when using the straight-back, bent-knee method of lifting recommended by the warehouses. The average working heart rate and the peak heart rate for female workers were significantly higher than those for male workers while there were no significant differences in performance index, energy expenditure, actual cases, weight and volume lifted/min. The average energy expenditure and heart rate for the male and the female workers were significantly higher than the acceptable limits. Time standards based on traditional work measurement techniques were physiologically unacceptable, especially for female workers.