24-hour movement behaviours in the early years, potential behavioural determinants and prospective associations with growth, motor and social-emotional development: the My Little Moves study protocol.

Introduction: The early years are a critical period for establishing healthy 24-hour movement behaviours (physical activity, sedentary behaviour and sleep), yet studies examining prospective associations between all 24-hour movement behaviours and young children's growth and development are lacking. The My Little Moves study aims to (1) examine the prospective association between 24-hour movement behaviours of young children (ie, 0-4 years) and their growth, motor and social-emotional development; and (2) explore potential determinants of young children's 24-hour movement behaviours from an ecological perspective, to inform public health strategies aimed at promoting healthy behaviours and development.

Methods And Analysis: My Little Moves is a longitudinal observational cohort study, with data collection at baseline, and after 9 and 18 months follow-up. Data are collected in three subcohorts. In all subcohorts, 24-hour movement behaviours are assessed by parent-report. Additionally in subcohort 1, data on potential determinants are collected by parental questionnaires, including child, parental and environmental factors. In subcohort 2, social-emotional development is assessed using the Dutch version of the Bayley Scales of Infant and Toddler Development-third edition (Bayley-III-NL) Social Emotional Scale. In subcohort 3, data on height and weight, gross motor development, using the Bayley-III-NL Gross Motor Scale, and 7 consecutive days of 24-hour accelerometer data are collected. Hybrid model analyses are used to assess the prospective associations of 24-hour movement behaviours with young children's growth and development. Potential determinants of young children's 24-hour movement behaviours are explored using regression analysis.

Ethics And Dissemination: The Medical Ethics Committee of the VU University Medical Center approved the protocol for the My Little Moves study (2022.0020). The results of this study will be disseminated through the network of all authors, to inform public health strategies for promoting healthy 24-hour movement behaviours and contribute to the evidence-base of recommendations for ideal 24-hour movement behaviours in young children.