Predicting Trunk Kinematics from Static Task Parameters

Abstract

Many of the current ergonomic assessment tools available to industry take static "snapshots" of manual material handling (MMH) tasks to assess the hazards of a job. These tools are valuable to industry in that they provide a quick and inexpensive assessment of the task. However, these tools do not evaluate the trunk kinematics occurring during the task. As previous research has shown, trunk kinematics play an important role in assessing the stress placed on a person's low back. The goal of this study was to provide a model that predicts the trunk kinematics as a result of static task parameter inputs.

A three-dimensional electrogoniometer worn on the subject's low back (Lumbar Motion Monitor (LMM)) was used to record the effects of task parameters on trunk kinematics during a lifting task. Task parameters consisted of the inputs to the NIOSH Lifting Equation: the beginning and ending asymmetry location (five levels), horizontal distance (two levels), vertical height (three levels), and weight (two levels). Study results showed a good ability to predict the trunk kinematics in the sagittal plane, but a very low ability in the coronal and transverse planes. Using the results of this study to calculate the LMM Model's Probability of High Risk Group Membership (PHRGM) resulted in an average absolute error of 8.07. Improvements in the ability to accurately predict the PHRGM were achieved when the MMH lifts evaluated were kept within the parameters of this research. The results of this research provide ergonomists with trunk kinematics information from the static task parameters that can be used during the ergonomic assessment of a MMH lift.