To evaluate the effects of Tai Chi—a mind-body exercise--on age-related loss of physiological complexity (using fractal and entropy based measures), and to understand the relationship between complexity, function and adaptability, we will conduct a two-arm prospective randomized clinical trial. Our overarching goal is to evaluate if six months of Tai Chi training, compared to a waitlist control receiving standard medical care, can enhance physiological complexity and adaptability in older Tai Chi-naïve adults. Secondary goals of the study are to characterize the relationship between complexity biomarkers, measures of function, and resilience. This pilot study will inform a future more definitive trial by providing information on recruitment and retention, compliance, dose-dependent effects, preliminary estimates of effect size, and the optimal biomarkers of complexity, function, and adaptive capacity.