CHAPTER 3
 METHODS

 Parametric Model Structure

 A generic, parametric 3D full-body kinematic model was constructed with

AutolevTM (Online Dynamics, Inc., Sunnyvale, CA) as a 14 segment, 27 DOF linkage

joined by a set of gimbal, universal, and pin joints (Figure 3-1, Table 3-1). Comparable

to Pandy's (2001) model structure, 3 translational degrees of freedom (DOFs) (qi, q2, and

q3) and 3 rotational DOFs (q4, q5, and q6) express the movement of the pelvis in 3D space

and the remaining 13 body segments comprise four open chains branching from the

pelvis segment. The locations and orientations of the joints within corresponding body

segments are described by 98 patient-specific model parameters. In other words, the

patient-specific model parameters designate the geometry of the model containing the

following joints types: 3 DOF hip, 1 DOF knee, 2 DOF ankle, 3 DOF back, 2 DOF

shoulder, and 1 DOF elbow. Each joint is defined in two adjacent body segments and

provides a mechanical approximation connecting those segments (Figure 3-2). For

example, the knee joint axis is simultaneously established in the femur coordinate system

and the tibia coordinate system.

 A modified version of the Cleveland Clinic marker set (Figure 3-3) and a static

motion-capture trial is used to create segment coordinate systems and define static and

dynamic marker locations in these coordinate systems. Institutional review board

approval and proper informed consent were obtained before human involvement in the

experiments. The marker data collection system was a HiRes Expert Vision System