Biomechanical Analysis of a Complex Dynamic Task via Integrated Motion Capture and 3DSSPP

Determining the biomechanical demand of tasks that involve a wide range of postures typically requires the use of motion capture techniques to accurately measure the range of body positions throughout the task. Although there is obviously motion involved in such tasks, a biomechanical analysis can be performed using quasi-static methods provided the tasks do not involve significant accelerations. One commercial software tool for performing such analyses is the Three Dimensional Static Strength Predictor Program (3DSSPP) produced by the University of Michigan. While the postural data obtained via motion capture methods can be manually input into 3DSSPP, this typically involves either the use of a two-dimensional projection of the three-dimensional visual image to estimate the joint angles, or the user may perform a visual comparison of an actual image of the task with the 3DSSPP image to obtain matching postures in the two programs. However, an automated data transfer method from the motion capture software to 3DSSPP is both more efficient and accurate. This paper presents an integrated method of motion capture and biomechanical analysis utilizing a software script for converting the data from version 1.1 of the Cortex motion capture software to a batch file for direct input into 3DSSPP. The application of this direct data input method was demonstrated by using it to analyze the physical demands of pulling the starter cord on two different models of lawn mowers.