Background and rational: Although home-based cardiac rehabilitation (CR) programs have been shown to produce significant increases in exercise capacity, adherence to these programs has been challenging. Consequently, it is critical to identify key theoretical determinants of exercise during home-based CR to inform the development of behavioral interventions to help ameliorate the adherence problem. Therefore, the present study examined the utility of the theory of planned behavior (TPB) in explaining exercise behavior during home-based CR.

Participants and Procedure: Once ethical approval was obtained, the home-based CR staff was asked to inform the patients about the current study at the patient's initial orientation meeting. Patients who were interested in the study were asked to speak to the research coordinator. At that time, the patients were given an information letter, an informed consent, and had the study explained to them in more detail. If they were interested in participating, they signed the informed consent and took a questionnaire home with them that included the theory of planned behavior questions in addition to the demographic and medical questions. They were asked to complete the questionnaire and take it back to their initial session (on-site) with their CR home based mentor assigned to them for the six-month program. In order to obtain the three and six-month follow-up data, the same questionnaire plus an exercise instrument was mailed to the patients two-weeks prior to their regularly scheduled follow-up assessments at the hospital with their mentor, at which time, the research coordinator met the patients to obtain the questionnaire and to provide the patient with their incentive (ie, $13.00 in cash to cover their parking costs).

Results: 76 out of 114 patients agreed to participate in the study. The average age was 62.64 (SD = 10.98), they went to school for approximately 13.77 years (SD = 3.12), their BMI was 29.24 (SD = 4.85), and the majority were male (76%), married (80%), white (93%), retired (57%), and had an income less than $60,000 (60%). Path analyses showed that attitudes and perceived behavioral control significantly predicted intention for both time intervals (ie, baseline to three months, three months to six months), whereas subjective norm only predicted intention within the first three months. Intention significantly predicted implementation intention, which in turn, significantly predicted exercise for both time intervals. Finally, several underlying accessible beliefs were significantly related to exercise for both time intervals.

Conclusion: The TPB is a promising theoretical framework to explain exercise intentions and behavior during home-based CR. Fortunately, numerous underlying accessible beliefs were also identified that could be potentially targeted in a TPB-based exercise intervention for these patients.