Kinematics and Dynamics

 Human kinematics is the study of the positions, angles, velocities, and accelerations

of body segments and joints during motion. With kinematic data and mass-distribution

data, one can study the forces and torques required to produce the recorded motion data.

Errors between the biomechanical model and the recorded motion data will inevitably

propagate to errors in the force and torque results of dynamic analyses.

 Optimization

 Optimization involves searching for the minimum or maximum of an objective

function by adjusting a set of design variables. For example, the objective function may

be the errors between the biomechanical model and the recorded motion data. These

errors are a function of the model's generalized coordinates and the model's kinematic

parameters such as segment lengths, joint positions, and joint orientations. Optimization

may be used to modify the design variables of the model to minimize the overall fitness

errors and identify a structure that matches the experimental data very well.

 Limitations of Previous Methods

 The literature contains a number of examples that use techniques, with or without

optimization, to assist in the development of subject-specific joint models within a larger

computational model. Several authors have presented methodologies to predict joint

locations and orientations from external landmarks without using optimization (Bell et

al., 1990; Inman, 1976; Vaughan et al., 1992). However, a regression model based solely

upon population studies may not accurately portray an individual patient. Another study

demonstrated an optimization method to determine the position and orientation of a 3

link, 6 DOF model by minimizing the distances between model-determined and

experimental marker positions (Lu and O'Connor, 1999). A model optimally positioned