Emily R Medd, Mark R Beauchamp, Chris M Blanchard, Valerie Carson, Benjamin Gardner, Darren ER Warburton, Ryan E Rhodes

Regular physical activity (PA) participation has many important physical and psychological health benefits, managing and preventing over 25 chronic conditions. Being more physically active as a child is associated with being more active as an adult, but less than 10% of Canadian children are achieving the recommended PA guidelines of 60 minutes per day of moderate to vigorous PA. Parental support is a predictor of child PA, but parent intention to support child PA does not always predict enacted support. Targeting factors that assist in the sustainability of parent support behaviour of child PA may have an impact on child PA. The purpose of this study is to evaluate an intervention designed to promote habit formation of parental support (HABIT, independent variable) on child PA (dependant variable) compared with a planning and education group (PLANNING) and an education only group (EDUCATION). The three conditions will be compared using a 6-month longitudinal randomised trial. Eligible families have at least one child aged 6-12 years who is not meeting the 2011 Canadian PA Guidelines. Intervention materials are delivered at baseline, with check-in sessions at 6 weeks and 3 months. Child's moderate-to-vigorous PA, measured by accelerometry, is assessed at baseline, 6 weeks, 3 months and 6 months as the primary outcome. At baseline and 6 months, children perform fitness testing. Parents and children complete questionnaires at all timepoints. So far, 123 families have been recruited from the Greater Victoria and surrounding area. Recruitment will be continuing through 2020 with a target of 240 families. This protocol has been approved by the University of Victoria Human Research Ethics Board (Victoria, Canada). Results will be shared at conferences as presentations and as published manuscripts. Study findings will be made available to interested participants. NCT03145688; Pre-results.