Evaluation of a physical activity intervention for new parents: protocol paper for a randomized trial

BACKGROUND: Identifying critical life transitions in people’s physical activity behaviors may illuminate the most opportune intervention apertures for chronic disease prevention. A substantive evidence base now indicates that parenthood is one of these critical transition points for physical activity decline. This study will examine whether a brief theory-based intervention can prevent a decline in physical activity among new parents over 6 months following intervention. This study protocol represents the first dyad-based physical activity initiative in the parenthood literature involving both mothers and fathers; prior research has focused on only mothers or only fathers (albeit limited), and has shown only short-term changes in physical activity. This study will be investigating whether a theory-based physical activity intervention can maintain or improve moderate to vigorous intensity physical activity measured via accelerometry of new parents over a 6 month period following intervention compared to a control group. METHODS: This study is a 6-month longitudinal randomized controlled trial. Parents are measured at baseline (2 months postpartum) with two assessment points at 6 weeks (3.5 months postpartum) and 3 months (5 months postpartum) and a final follow-up assessment at 6 months (8 months postpartum). The content of the theory-based intervention was derived from the results of our prior longitudinal trial of new parents using an adapted theory of planned behavior framework to predict changes in physical activity. RESULTS: A total of 152 couples have been recruited to date. Sixteen couples dropped out after baseline and a total of 88 couples have completed their 6-month measures. DISCUSSION: If the intervention proves successful, couple-based physical activity promotion efforts among parents could be a promising avenue to pursue to help mitigate the declines of physical activity levels during parenthood. These findings could inform public health materials and practitioners. TRIAL REGISTRATION: This trial has been registered with the Clinical Trials Registry maintained by the National Library of Medicine at the National Institutes of Health on April 19, 2014. The registration ID is NCT02290808. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (10.1186/s12889-017-4874-7) contains supplementary material, which is available to authorized users.