This study is being done to find out how age, activity level, and the presence of heart disease affect the way the body controls blood pressure. A total of 80 individuals will be recruited for the study, and will consist of two groups: sedentary healthy individuals and those with coronary artery disease (CAD). Each group will undergo screening tests, including history, questionnaires, physical exam, lab tests, treadmill exercise tolerance test, and maximal exercise test. These screening tests will be repeated at 3 months and 6 months.

The study involves 20 visits over a 6-month period. An exercise-training program will be designed for the individual's fitness level. During the first month, the individual will be supervised while exercising at Spaulding Rehabilitation Hospital, but after that may choose to exercise at home or in a fitness center. These exercise sessions will take place 3-5 times per week for 15-40 minutes per session based on the individual's exercise program, increasing to 4-6 times per week for 30-60 minutes per session after the first month. Participants will be required to visit Spaulding Rehabilitation Hospital a minimum of once every two weeks so that information can be collected from a heart rate monitor.

Testing is done at the beginning and end of the exercise-training intervention period to determine what effect the intervention has had on the individual's blood pressure regulation. This testing consists of 2 sequential study days. During the first day's testing, which will last about 2 hours, the participant will receive 8 low doses of atropine to alter vagal effects. On the second day, which will take about 4 hours, the participant will receive sodium nitroprusside, phenylephrine, and low-dose atropine while sympathetic nervous activity is recorded. Differences in blood pressure regulation pre- and post-training will be studied.