The purpose of the study is to compare a telephone-administered physical activity counseling program delivered by a person or by a telephone-linked computer system and test their relative benefits in improving regular physical activity among adults ages 55 and older.

Two hundred and twenty five healthy, sedentary men and women ages 55 and older will be randomly assigned to one of three conditions: 12 months of physical activity counseling delivered by a human counselor, 12 months of physical activity counseling delivered by a telephone-linked computer system, or a 12-month attention-control condition (a health education class). Data on physical activity participation and related quality of life indicators (e.g., improved physical functioning, fitness, sleep) will be collected at baseline, 6 months, 12 month post-test and 18 month follow-up. The primary hypotheses are:

• participants in either physical activity counseling condition will show greater improvements in physical activity participation at 12 months compared to the attention-control condition;
• participants in the human counselor condition will show greater improvements in physical activity at 12 months relative to the computer condition; and
• participants in the computer condition will show better maintenance of physical activity between 12 and 18 months compared to participants in the human counselor condition.

Inclusion Criteria:

• Men and women ages 55 and older
• Free of any medical condition that would limit participation in independent exercise
• Not currently engaged in a regular pattern of physical conditioning
• Free of clinical psychopathology
• Stable on current medications
• Planning to remain in the geographic area through the duration of the trial
• Able to read and speak English sufficiently to understand protocol materials
• Can use the telephone unaided
• Willing to accept random assignment to any study condition

Exclusion Criteria:

• Under the age of 55
• Currently under treatment for an acute, serious medical condition (e.g., cancer, heart disease, stroke)
• Physically active on a regular basis (i.e. performing more than 60 minutes per week of aerobic physical activity of at least a moderate intensity)
• Unstable and/or uncontrolled on medications for high blood pressure or depression
• Unable or unwilling to use a telephone unaided
• Unwilling to accept random assignment to study condition