Physical Activity and Cognition Study

Inclusion Criteria: * Non-smoking * Age between 55-85 years * Sedentary status (physically inactive; not participating in at least 30 minutes of moderate intensity physical activity on at least three days per week for at least three months) * Generally healthy men and women * Living in the greater Boston area * Available for the 4 month duration of the study * Native-English speaking or fluent in English (must have attended elementary school and higher in English) Exclusion Criteria: * Poor vision that cannot be corrected with glasses or contact lenses * Presence of an acute infection * Diagnosis of kidney failure * Diagnosis of liver disease * Diagnosis of thyrotoxicosis/hyperthyroidism * Diagnosis of cancer * Past or present conditions that affect cognitive functioning: 1. learning disability 2. neurological disorders or conditions (movement disorder, history of head trauma or stroke, epilepsy, etc.) 3. psychiatric disorders or conditions (depression, anxiety disorder, etc.) * Past or present conditions that are counter indicators for participation in cardio-respiratory fitness assessment and moderate-intensity physical activity: 1. heart conditions (e.g. heart attack, arrhythmias, etc.) 2. circulatory conditions (e.g. uncontrolled hypertension, leg claudication, high cholesterol, etc.) 3. respiratory conditions (e.g., asthma or lung conditions, such as chronic obstructive pulmonary disease, acute bronchitis, acute common cold, lung cancer, pneumonia, etc.) 4. current musculoskeletal impairments (e.g. fractures, hemiplegia, chronic joint pain, arthritis, osteoporosis, not able to walk comfortably without assistance, etc.) 5. diagnosis of electrolyte disorder or abnormality 6. presence of diabetes mellitus * Obesity * Prescription medication or other drugs that treat heart, lung, or circulatory conditions (e.g. beta blockers, bronchodilators, etc.) * Prescription medication or other drugs that affect chemicals in the brain (e.g. antidepressants, anxiolytics, etc.) * Implanted medical devices, such as a pacemaker or defibrillator * Unavailable for the approx. 4-month duration of the study