We describe a thorough quantitative analysis of a novel, kinematic model of the human body used for the tracking and extraction of gait variables. The model includes multiple levels of structural complexity coupled with absolute and probabilistic kinematic constraints; while the relevant variables include velocity, stride length, stance width, and stance times. The analysis is based on the accuracy of extracted gait variables for various permutations of the proposed kinematic body model. Using patterns of complex human motion collected from a multi-camera video monitoring system, we demonstrate the precise costs and benefits associated with various model components and kinematic constraints.