Control Entropy of Gait: Does Running Fitness Affect Complexity Of Walking?

Background: The purpose of this study was to determine if trained runners exhibited different complexity of walking than untrained individuals. Methodology: Trained runners (T) and untrained controls (UT) performed two incremental walking trials that spanned 2, 4 and 6 km/h. Complexity was assessed through control entropy (CE), which was determined from high resolution accelerometry collected from the center of mass for three axes (VT, ML, AP). CE was compared between groups using a non-linear statistical approach to account for potentially non-stationary dynamical systems. Principle Findings: Within groups, there were no significant differences in the shape of the CE response between axes in UT, but in T, AP was significantly different from VT and ML (p < .05). Between groups, there were no significant differences in the shape of the CE response by axis. CE was significantly lower in the VT and ML axes (p < .05), but CE was not different in the AP axis (p = 0.16). Conclusions/Significance: These results show that T and UT individuals exhibit similar CE responses over time during incremental walking, but CE is lower in T versus UT in both the vertical and mediolateral axes. Lower CE in the T group is indicative of lower complexity, indicating that T runners are more constrained while walking than UT