Quantifying Complexity and Variability of Gait Phase Portraits

Injuries to the lower extremity can limit joint motion and alter movement patterns of the limb segments during gait. Researchers have also found changes in variability and complexity as a function of injury. Injury or joint pain appears to decrease gait cycle variability [1]; however, the results on complexity are less clear. While some researchers have found a decrease in complexity due to disease and aging, e.g., [2], others have found an increase in complexity [3]. One of the goals of the current work was to quantify changes in the variability and complexity of motion patterns as assessed using phase portraits.