Accuracy of a three-dimensional lumbar motion monitor for recording dynamic trunk motion characteristics

• Published in: International journal of industrial ergonomics Vol. 9; no. 1; pp. 75 - 87
• Main Authors: Marras, W.S., Fathallah, F.A., Miller, R.J., Davis, S.W., Mirka, G.A.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 1992
• Subjects: asymmetry; Back; kinematics; low back disorder; strength; trunk strength; Back; low back disorder; kinematics; asymmetry; strength; trunk strength
• ISSN: 0169-8141; 1872-8219
• DOI: 10.1016/0169-8141(92)90078-E

There has been an abundance of evidence in the past decade that indicates that the asymmetric positioning as well as the dynamic action of the trunk during work greatly affects the ability of a worker to perform a lifting task. This is true because trunk strength decreases as the trunk moves more asymmetrically and more rapidly. Loading of the spine is also believed to increase under these conditions, since significantly greater trunk muscle activity has been observed under these conditions. Therefore, we must begin to document the asymmetric positions as well as the dynamic motion characteristics of the trunk when workers are exposed to various work tasks. This paper describes a lumbar motion monitor (LMM) that has been developed for this purpose. The LMM is an exoskeleton of the spine that is instrumented so that instantaneous changes in trunk position, velocity and acceleration can be obtained in three-dimensional space. The current study has assessed the accuracy and reliability of the LMM to measure such motion components. The results of this analysis indicate that the LMM is extremely reliable and very accurate. This study has shown that the LMM is about twice as accurate as a video-based motion evaluation system. The benefits and implications of using an LMM for work assessment and clinical use are discussed.