Visualizing changes in lower body coordination with different types of foot orthoses using self-organizing maps (SOM)

Human movement involves the coordination of individual segments controlled by the central nervous system and powered by the muscles. However, visualization of this high-dimensional coordination between kinematic and kinetic parameters is challenging. The purposes of this study were (a) to identify differences in lower extremity coordination between different types of foot orthoses using Kohonen self-organizing maps (SOM) and (b) to demonstrate the SOM visualization of high-dimensional coordination in gait. This study used gait data for twenty subjects while running in four different orthotic conditions (control, posted, molded, and posted-molded) from a previous study. Data for one exemplar participant was used to demonstrate the visualization technique. In this visualization, areas on an output map represent certain characteristics of the gait cycle. By comparing trials of gait in different orthotic conditions a visual analysis of high-dimensional coordination is possible. Posting orthoses were shown to reduce and molded orthoses were shown to increase ankle mobility, respectively. However, when posting and molding were combined, the effects of the molded orthoses over-rode those of the posted orthoses. In fact, trials using posted-molded orthoses enhanced the effects of molded orthoses. SOMs may contribute to a better understanding of changes in the coordination of kinematic and kinetic variables at certain phases of the gait cycle under different conditions.