THE IMPORTANCE OF CONSISTENT KINEMATIC DATA IN THE INVERSEDYNAMIC ANALYSIS OF BIOMECHANICAL MODELS

Abstract

INTRODUCTION: The evaluation of the muscular actions and internal forces of human articular joints is of major importance in different areas of medicine, sports, physical rehabilitation or biomedical engineering. There is no experimental methodology that can directly measure these forces. Among the numerical procedures that can be applied, inverse dynamics based methods are still the most commonly used numerical tools. Their use requires that the kinematics of human motion, i.e., the positions, velocities and accelerations of the anatomical points, be known in advance. This is obtained by standard reconstruction methods based on the DLT technique (Aziz and Karara, 1971). Moreover, the equations of motion for the system must be associated to a biomechanical model (Celigueta, 1996; Silva et al., 1997). The muscle action may be obtained by having each particular group of muscles, defined as those with similar functions and common anatomical insertions, modeled independently and included in the biomechanical model (An et al., 1995). This leads to an indeterminate problem, in terms of the unknown forces, that can be solved using the optimization theory (Pedotti et al., 1978). Alternatively, the actions of the different muscle groups can be lumped as moments about anatomical joints leading to a determinate inverse dynamics problem (Winter, 1991). Regardless of the biomechanical model used or of the way the muscle actions are described, the results obtained from the inverse dynamic analysis are related to the quality of the kinematic data supplied. The problem of the consistency of this kinematic data with respect to the biomechanical model used is addressed in this work, it being shown that the quality of the inverse dynamics analysis results is highly dependent on the data kinematic consistency.