From stability to complexity: A systematic review protocol on long-term divergence exponents in gait analysis

Long-term divergence exponents derived from nonlinear gait analysis (maximum Lyapunov exponent method) have recently been reinterpreted as measures of gait complexity rather than stability. This shift necessitates a comprehensive review of existing literature. This systematic review protocol aims to critically examine studies using long-term divergence exponents in gait analysis. The focus will be on reconciling previous findings with current understanding, evaluating methodological approaches, and synthesizing comparable results. We will search Web of Science (including MEDLINE) for peer-reviewed articles published between 2001 and 2024 that report long-term divergence exponents calculated using Rosensteins algorithm in human gait studies. Two independent reviewers will screen articles and extract data on study characteristics, methodological specifications, and result interpretations. Primary outcomes will include tracking how result interpretations have evolved over time and identifying potential reinterpretations based on current knowledge. Secondary outcomes will address methodological standardization. Data synthesis will primarily be narrative. Where possible, meta-analyses will be conducted for studies with comparable methods and objectives. Given the expected exploratory nature of many included studies, a narrative assessment of methodological quality will be performed instead of a formal risk of bias evaluation. This review will consolidate understanding of long-term divergence exponents as measures of gait complexity and automaticity, establish standardized computational methods, and inform future research and clinical applications in gait analysis.