The objective of this randomised controlled trial is to examine the effectiveness of a theory-driven behavioural change intervention on total sedentary time (primary outcomes), moderate-to-vigorous physical activity time, intention of behavioural change, future time perception, behavioural prepotency, self-regulation capacity, and exercise capacity in individuals with coronary heart disease.

Hypotheses:

Compared to the participants in the control group, participants in the intervention group will demonstrate:

1. Significantly less total sedentary time
2. Significantly improved MVPA time,
3. Significantly better intention of behavioural change,
4. Significantly higher level of behavioural prepotency,
5. Significantly enhanced self-regulation capacity, and
6. Significantly greater future time perception
7. Significantly better exercise capacity at the immediate post-intervention (T1), the 1-month post-intervention (T2), and the 6-month post-intervention (T3).

Participants will:

Participants in the intervention group will participate in a theory-driven behavioural change intervention over three months, comprising four individual face-to-face sessions (45 minutes each) and four individual telephone sessions (20 minutes each), along with the usual care.

Participants in the attention control group will continue to have the usual care, which includes regular follow-up at the cardiac clinic. Education sessions, consisting of information about healthy lifestyles, except physical activity and sedentary behaviour, with the same schedule as the intervention group, will be provided to account for potential attention effects from contacts.

Coronary heart disease is a worldwide health problem and a major contributor to disability, with a high prevalence of 315 million cases globally in 2022. Promoting movement behaviours, which are characterised by having an adequate amount of physical activity and replacing sedentary behaviour with physical activity of all intensities, is beneficial for cardiometabolic health and thus secondary prevention. However, reviews of interventional studies indicate that currently available non-pharmacological interventions are effective in increasing the amount of physical activity, yet limited attention is given to the reduction of sedentary behaviour in current cardiac rehabilitation. Therefore, it is imperative to develop an non-pharmacological intervention targeting sedentary behaviour for adults with coronary heart disease based on the synthesised scientific evidence. The design of the theory-driven behavioural change intervention is based on the findings of our published systematic review and the implications of the qualitative study.

This randomised controlled trial evaluate a theory-driven behavioural change intervention for individuals with coronary heart disease. The objective of the study aims to examine the effectiveness of the intervention in reducing total sedentary time (primary outcome) and improving MVPA, behavioural intentions, future time perception, behavioural prepotency, self-regulation capacity, and exercise capacity in a larger sample.

Inclusion Criteria:

1. Adult 18 years old and above
2. Diagnosed with coronary heart disease within one year
3. Engaged in MVPA less than 150 minutes per week and a minimum of 8 hours total sedentary time per day, both assessed using the Global Physical Activity Questionnaire
4. Able to communicate in Cantonese
5. Obtained medical clearance for physical activity (no medical contraindications to exercise, including walking)
6. Being able to understand and give informed consent
7. Having telephone access, text messaging services or WhatsApp

Exclusion Criteria:

1. Cannot perform brisk walking exercise
2. Unable to perform PA independently
3. Cognitive impairments, as indicated by an abbreviated mental test score of less than 7
4. Currently enrolled in another clinical trial focusing on limiting SB with/without enhancing PA
5. Doctor-diagnosed psychiatric illness

The research team does not have plans to proactively or automatically make the individual participant data (IPD) from this study available to other researchers. However, the IPD may be shared upon request, provided that the requesting party has a valid scientific or medical rationale and obtains the necessary approval from the research team.

Any requests for access to the study's IPD will be reviewed on a case-by-case basis by the research team. Factors that will be considered in evaluating such requests include:

Scientific merit and validity of the proposed use of the data Qualifications and track record of the requesting researcher or research team Alignment with the original study objectives and participants' consent

The study employs single masking, where only the outcome assessor is blinded. Due to the nature of the interventions, masking the participants and intervention providers is not feasible.