Acceptability Rating in Manual Materials Handling: An Experimental Evaluation of Psychophysical Criteria

Abstract

Most recommendations on manual materials handling are based on laboratory experiments where lifting was performed repetitively in the sagittal plane (Ljungberg et al., 1982 and NIOSH, 1981). Since occupational work often implies a more complex work organisation and seldom includes sagittal plane lifting in the ‘text-book sense’ these recommendations may not be applicable. The laboratory experiments reported here were therefore based on field studies (Ljungberg et al., 1983 and Ljungberg et al., 1984) of actual vocational activities, in occupations with a well-known high incidence of low back pain, e.g. warehouse workers and nursing aides (Figure 1). In order to quantify the lifting a pair of wooden shoes equipped with four strain gauge bridges were used (Hägg, 1981). The signals were analyzed as regards weight of the burden, lifting frequency and duration, number of steps taken and a code for balance. Heart rate and pulmonary ventilation were registered (Figure 2).