Therefore, the purpose of this research is to examine the role of an organized 6-month cardiovascular exercise intervention trial on electrocortical (event-related brain potential) and behavioral measures (reaction time) of executive control. In addition, a non-cardiovascular exercise control group that participates in a 6-month stretching and toning program will be used for comparison. Participants will be measured before and after exercise training during engagement in several tasks designed to elicit different executive functions (e.g., discrimination, task switching, inhibition). Each task also contains a non-executive condition that will be used for comparison to examine the specificity of exercise participation of cognitive functioning. A secondary aim of this project is to determine the effects of an acute bout of exercise on cognitive functioning. Both groups will participate in several bouts of exercise followed by immediate measurement on the tasks outlined above to determine whether acute exercise has beneficial effects on executive processes. The significance of this research may include the increased understanding of factors related to the amelioration of age-related decrements in central nervous system functioning and recommendations for the maintenance of cognitive health during the later stages of life.