Specific Aim #1: To determine if 6 months of Tai Chi training can increase complexity, function, and adaptive capacity of multiple physiological systems in older healthy adults. Specific Aim #2: To determine the relationships between biomarkers of physiological complexity, conventional measures of function and adaptive capacity. Statistical regression models will be used to determine relationships, both at baseline and overtime, between a) complexity biomarkers and measures of physical and cognitive function, and b) complexity biomarkers and adaptive capacity. Elucidating these relationships will further inform the interpretation of complexity biomarkers and provide insights into underlying component mechanisms contributing to complex physiological dynamics.