Angular displacement of torso during lifting: A system comparison of two measuring methods

Abstract

This paper introduces a study which was conducted to evaluate two different methods used to measure trunk kinematics during a set of controlled lifting tasks. The following two methods were compared in a laboratory study: (1) an opto-electronic detection method using the Selspot 1 method, and (2) a new Miniature electronic Inclinometer method. The comparison revealed that, with care in calibration, the two methods display similar torso angle measurements for a large variety of test conditions. Cross-correlation between the angle estimates averaged (rmean = 0.814) for a combination of the following lifting variables: posture of lifting, lifting height, weight of load, and horizontal distance. Variation in the correlation coefficient between the two measuring methods shows acceptable positive correlation and consistent agreement in angle trajectory over time at Thoracic (at level 5), consistency was obtained at Lumbar (level 5) and Cervical (level 4) levels. Factors affecting the performance of the two measuring methods are analyzed and the pros and cons of the method are discussed. The findings argue for the use of the new Miniature Inclinometer since it is inexpensive when compared to the Selspot 1 measuring system, provides direct angle measurements and is an easy to use technique.