A simple apparatus using inclinometer for monitoring working postures

Abstract

A new apparatus was developed for evaluating a load on the low back caused by working postures by measuring upper body inclination. This apparatus consists of an inclinometer and a portable unit. The inclinometer that uses a magnetic resistance sensor is attached to the upper body of the subject. The portable unit, controlled by a one-chip CPU, is enclosed in a cloth case and carried by the subject on his waist belt. The inclination is measured at a certain interval and recorded in the memory of the portable unit. All the recorded data are later transferred to a host computer and then analyzed. According to the theoretical analysis by using a simple mathematical model, upper body inclination changes according to the height of work places, and one cm difference in height causes more than one degree of upper body inclination. A model work of material handling was carried out to collect sample data. Two male subjects lifted ten boxes onto a platform from a stand in several heights. Both stooped and squat lifting methods were used as the lifting protocol. The mean and standard deviation (SD) of the upper body inclination during work decreased according to the lift distance only in stooped lifting. As a practical application, working postures during the task of changing diapers for handicapped people were analyzed with our apparatus. A female subject changed diapers eight times at different height of beds. The mean value of inclination decreased according to the height of the beds. The SD was almost constant in all data, because most of the work was performed at the bedside and the working posture was rarely changed. © 1994, Japan Society for Occupational Health. All rights reserved.