Engagement in physical activity (PA) can positively influence the health of older adults and reduce the risk of many chronic diseases (28). Previous studies support the assertion that PA delays the onset of cognitive decline and the incidence of dementia or Alzheimer_s disease associated with aging (1,2,31). Most existing studies, however, have relied on self-reported PA assessments, which may be influenced by recall biases, health status, depression, cognitive ability, and other factors, especially for older adults. Objective PA measures have been increasingly used to overcome limitations of self-report measures, but the sample sizes of those present studies were relatively small (10,32). More objective assessments of PA are needed to better define the dose–response association of various PA outcomes with cognitive function.