The STRENGTH Study: A cluster randomised controlled trial of the effect of a behaviour change intervention added to cardiac rehabilitation on physical activity adherence

Q: What is the clinical evidence from this study?

Study design: RCT. Population: Coronary heart disease in maintenance stage cardiac rehabilitation (n=96). Intervention: Behaviour change intervention added to maintenance stage cardiac rehabilitation vs. Standard care (community-based maintenance stage cardiac rehabilitation classes alone). Primary outcome: Change from baseline to 6 months in daily minutes of moderate-to-vigorous physical activity (MVPA) and daily step counts measured via ActiGraph accelerometer (p=0.97).

Clare T. M. Doherty; Mark A. Tully; Jason J. Wilson; Leonie Heron; Helen McAneney; Victoria Irving; Lisa Spratt; Rachel O’Reilly; Kim Kensitt; Nicole E. Blackburn

doi:10.1371/journal.pone.0345293

March 24, 2026PLoS ONEOpen Access

The STRENGTH Study: A cluster randomised controlled trial of the effect of a behaviour change intervention added to cardiac rehabilitation on physical activity adherence

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Key result

Behaviour change intervention added to maintenance cardiac rehabilitation fails to improve physical activity levels.

P=0.97
n=96

Why the study?

It was unknown whether adding a behaviour change intervention to cardiac rehabilitation could promote and maintain physical activity levels beyond standard care timeframes.

Does adding a multi-component behaviour change intervention to maintenance stage cardiac rehabilitation improve 6-month physical activity adherence (daily MVPA and step counts) compared to standard maintenance cardiac rehabilitation alone in patients with coronary heart disease?

Key Points

To determine whether adding a behaviour change intervention to standard maintenance stage cardiac rehabilitation increases and sustains physical activity adherence over six months.
Cluster randomized controlled trial conducted across six community-based maintenance cardiac rehabilitation classes (NCT05705310).
Enrolled 96 participants with coronary heart disease (mean age 65.04 ± 8.38 years; 75% male) assigned to either standard care (n = 44) or a behaviour change intervention (n = 52).
Physical activity was assessed at baseline, 12 weeks, and 6 months using an ActiGraph GT3X+ accelerometer to evaluate daily steps and moderate-to-vigorous physical activity (MVPA).
No significant difference occurred between intervention and control arms for change in daily MVPA (W = 1218.00, p = 0.97) or daily step counts (W = 1275.00, p = 0.47) at six months.
Repeated-measures interaction models across timepoints showed no significant effect of condition on daily MVPA (F 5,1 = 0.57, p = 0.72) or daily step counts (F 5,1 = 0.25, p = 0.94).
Secondary outcomes, including physical activity self-efficacy, health-related quality of life, and mental wellbeing, did not differ significantly between groups.

Study Design

Type

RCT (n=96)

Blinding

Open-label

Randomization

Cluster randomization at the level of the cardiac rehabilitation class with a stepped implementation sequence

Multicenter

Yes

Structured PICO

Does adding a multi-component behaviour change intervention to maintenance stage cardiac rehabilitation improve 6-month physical activity adherence (daily MVPA and step counts) compared to standard maintenance cardiac rehabilitation alone in patients with coronary heart disease?

P

Population

96 adults with coronary heart disease enrolled in community-based maintenance stage cardiac rehabilitation in Northern Ireland (mean age 65.04 years, 25% female), followed for 6 months.

I

Intervention

Multi-component behaviour change intervention added to standard maintenance stage cardiac rehabilitation over 6 months, incorporating pedometer (Yamax Digiwalker CW-701) or personal wearable self-monitoring, weekly activity diaries, 6 weekly individual goal-setting reviews (targeting e.g. 10% weekly step increases), 3 subsequent monthly check-ins, and researcher-led group discussions on barriers, facilitators, and social support.

C

Comparator

Standard care community-based maintenance stage cardiac rehabilitation alone (typically two 60-minute supervised structured exercise sessions per week of moderate-intensity aerobic and resistance training, though delivered 1 day per week in reality, with extended access beyond 12 weeks; control participants received a pedometer after 6-month follow-up).

O

Outcome

Change in physical activity from baseline to 6 months, assessed by two co-primary outcomes measured over 7 consecutive waking days using an ActiGraph wGT3X-BT accelerometer: 1) daily minutes of moderate-to-vigorous physical activity (MVPA), and 2) daily step counts.surrogate

Main Result

Absolute Event Rate: -2.68% vs -2.84%

p-value: p=0.97

Adding a structured behaviour change intervention to community-based maintenance cardiac rehabilitation did not further increase physical activity or improve health outcomes at 6 months, though ongoing access to maintenance rehabilitation sustained high baseline activity levels in both groups.

Limitations

Deviations from the planned stepped-wedge rollout resulted in a cluster randomised trial with fewer clusters than planned, reducing statistical power.
Unblinded (open-label) design where participants knew their condition allocation.
High baseline physical activity levels already surpassing guideline recommendations limited realistic potential for improvement.
Extended, uncapped access to maintenance cardiac rehabilitation classes beyond 12 weeks in both groups may have masked intervention effects.
Declining adherence to tracking and goal-setting components over time, and no formal adjustment for multiplicity across the two primary outcomes.
Planned stepped-wedge rollout could not be fully implemented due to post-pandemic operational constraints, resulting in fewer clusters than planned and reduced statistical power.
Participants could not be blinded to group allocation.
High baseline physical activity levels (already surpassing BACPR and WHO MVPA guidelines) created a ceiling effect and potential selection bias toward healthier, more motivated participants.
Uncapped, extended access to maintenance cardiac rehabilitation classes beyond 12 weeks in both groups provided unanticipated ongoing support that may have masked intervention effects.
Waning adherence to intervention tracking (85% overall) and goal-setting (55% overall) over time, variable CR attendance, and no formal adjustment for multiplicity across the two primary outcomes.

Discussion

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Implication

Does not support adding behaviour change interventions to maintenance cardiac rehabilitation; confirms standard programs sustain activity without incremental gains.

Abstract

Background Coronary heart disease is the leading cause of global mortality, imposing significant health and economic burdens. Cardiac rehabilitation, including physical activity, can reduce coronary heart disease-related morbidity and mortality. We tested whether the addition of a behaviour change intervention to cardiac rehabilitation could promote and maintain physical activity achieved during cardiac rehabilitation, beyond standard care timeframes. Methods A cluster randomised controlled trial was conducted across six community-based maintenance stage cardiac rehabilitation classes. A total of 96 participants (mean age 65.04 ± 8.38 years; 75% male) received either standard care or a behaviour change intervention, with physical activity, measured with an ActiGraph GT3X+ accelerometer as the primary outcome. Results No significant differences in daily minutes of moderate-to-vigorous physical activity and steps per day, or any secondary outcomes, including self-rated health, quality of life, and mental wellbeing, were observed between the intervention and control groups at six months follow-up. These findings suggests that the behaviour change intervention did not significantly impact physical activity or health outcomes during maintenance cardiac rehabilitation. This may be attributed to high baseline physical activity levels among participants, and the extended cardiac rehabilitation support provided to both groups, potentially masking any intervention effects. Conclusion A behaviour change intervention added to standard maintenance stage cardiac rehabilitation did not improve physical activity or health outcomes. However, continued access to cardiac rehabilitation sustained high physical activity levels. Future research should disentangle the independent effects of behaviour interventions and ongoing cardiac rehabilitation support. Trial registration ClinicalTrials.gov NCT05705310

Cite This Study

Doherty et al. (2026) conducted an RCT in Coronary heart disease in maintenance stage cardiac rehabilitation (n=96). Behaviour change intervention added to maintenance stage cardiac rehabilitation vs. Standard care (community-based maintenance stage cardiac rehabilitation classes alone) was evaluated on Change from baseline to 6 months in daily minutes of moderate-to-vigorous physical activity (MVPA) and daily step counts measured via ActiGraph accelerometer (p=0.97). Adding a behaviour change intervention to maintenance cardiac rehabilitation did not significantly change daily MVPA (-2.68 vs -2.84 min, p=0.97) or step counts (-133.79 vs -431.83, p=0.47) at 6 months.

synapsesocial.com/papers/69c4cc98fdc3bde448918047 https://doi.org/10.1371/journal.pone.0345293

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The STRENGTH Study: A cluster randomised controlled trial of the effect of a behaviour change intervention added to cardiac rehabilitation on physical activity adherence

Key Points

Study Design

Structured PICO

Main Result

Limitations

Discussion

Implication

Abstract

Cite This Study

The STRENGTH Study: A cluster randomised controlled trial of the effect of a behaviour change intervention added to cardiac rehabilitation on physical activity adherence

Key Points

Study Design

Structured PICO

Main Result

Limitations

Discussion

Implication

Abstract

Cite This Study

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