This is a single-arm pilot trial to examine the feasibility, acceptability, and preliminary efficacy of the 12-week, phone-delivered, Midlife Activity, Stress reduction, Time Efficiency, Resilience, and Youthfulness (MASTERY) intervention, which utilizes positive psychology (PP), motivational interviewing (MI), and specific midlife modules (e.g., on time management, financial stress, caregiving stress, or occupational stress) to promote well-being and physical activity in mid-life adults.

This is a single-arm proof-of-concept trial of a phone-delivered positive psychology-motivational interviewing (PP-MI) intervention, with content adapted to midlife persons. Midlife adults with low physical activity were recruited from outpatient clinics, completed baseline outcome measures (including wearing an accelerometer to measure activity for one week), completed the 12-week MASTERY intervention, and then completed a follow-up session to obtain repeat outcome information. The intervention, which involved weekly phone sessions with a trained study team member, included the completion of PP exercises, setting physical activity goals, and completion of activities to reduce midlife-specific stressors. The primary outcomes were feasibility and acceptability, and secondary outcomes included accelerometer-measured physical activity and self-report outcomes.

Inclusion Criteria:

• Age 45-64 years at time of enrollment.
• Low physical activity (defined as ≤150 minutes/week of MVPA, in accordance with consensus recommendations for moderate or greater intensity aerobic physical activity and measured using a brief version of the well-validated International Physical Activity Questionnaire (IPAQ) scale.

Exclusion Criteria:

• Existing coronary artery disease. Coronary artery disease will be identified through review of the medical record, with clarification by participants' primary clinician if needed, as part of recruitment procedures. Existing coronary artery disease will be defined as a prior acute coronary syndrome (unstable angina or myocardial infarction) or diagnosed via cardiac catheterization.
• To meet criteria for a prior acute coronary syndrome, for myocardial infarction, patients must have experienced at least two of three World Health Organization criteria for an acute myocardial infarction: typical chest pain, elevated cardiac enzymes, and electrocardiographic changes consistent with myocardial infarction.
• For unstable angina, participants must have had new onset angina within 2 months, exacerbation of previous angina with rest pain or with minimal exercise, or angina within 2 weeks of myocardial infarction, with confirmation of this diagnosis by the patient's primary medical provider or inpatient treatment team; this definition has been used in prior trials.
• To meet criteria for coronary artery disease diagnosed at cardiac catheterization, participants must have had 50% stenosis of the left main artery or 70% stenosis of another coronary artery, consistent with consensus definitions of obstructive coronary artery disease.
• Cognitive disturbance precluding participation or informed consent, as identified using a six-item cognitive screen designed to assess suitability for research participation.
• Lack of available telephone.
• An inability to communicate in English.
• A condition limiting physical activity (e.g., arthritis, chronic obstructive pulmonary disease), identified by patient and medical record, confirmed by primary medical provider as needed.
• Participation in similar programs (e.g., mind-body interventions) as reported by patients.