BACKGROUND: Most (>90%) children with congenital health defects are not active enough for optimal health. Proactively promoting physical activity during every clinic visit is recommended, but rarely implemented due to a lack of appropriate resources.

METHODS: This cluster randomized controlled trial will implement an evidence-based, multi-faceted physical activity intervention. All eligible patients at small (London, ON), medium (Ottawa, ON) and large (Edmonton, AB) pediatric cardiac clinics will be approached, with randomization to intervention/control by clinic and week. Intervention patients will be counselled with 5 key physical activity messages, have questions about physical activity answered, and have access to a custom web site with personalized activity suggestions and support from a Registered Kinesiologist. The primary outcome is daily physical activity (number of steps, minutes of moderate-to-vigorous activity) assessed via pedometer one week per month for 6-months. Standardized questionnaires assess activity motivation and quality of life at baseline and end of study. Healthcare outcomes will be clinic visit time and contacts for physical activity concerns. Repeated measures ANCOVA will compare control/intervention pedometer outcomes, adjusting for covariates (alpha=0.05).

CONCLUSIONS: This trial aims to determine whether providing resources and protocols enables clinicians to counsel about physical activity as part of every pediatric cardiology appointment. Evaluations of healthcare system impact and intervention delivery in small, medium and large clinics will assess applicability for implementation in all pediatric cardiac clinics. The impact on physical activity motivation and participation will evaluate the effectiveness of this standardized approach for increasing physical activity in children with congenital heart defects.