The aim of this study is to develop, implement, and evaluate a novel intervention to increase physical activity and reduce sedentary behaviour among pre-school children, with the ultimate goal of reducing obesity among this age group. This study will provide evidence-based recommendations for reducing the prevalence of obesity among preschool-aged children, and the suggestions will help improve the physical activity intervention programme in preschoolers.

The pre-school-based I'm an Active Hero (IAAH) intervention with family involvement was developed in accordance with the Medical Research Council (MRC) framework for developing and evaluating complex interventions. The development phase consists of locating and synthesising existing evidence (such as what is already known about existing interventions) and finding and developing theories (e.g., developing a theoretical understanding of the expected process of behaviour change). The IAAH-intervention components are theory- and evidence-based; they were developed based on a comprehensive identification and evaluation of current and past community, preschool, and family-based physical activity and lifestyle change interventions, as well as recommendations from a recent systematic review and review of reviews.

Additionally, the IAAH-intervention component was informed by conducting a systematic review to identify promising intervention components, including behaviour change techniques, that are associated with interventions that were able to increase PA in the preschool age group. In addition to conducting a qualitative study with teachers and patients/guardians, investigators will also consult them on the intervention's content and duration. Investigators would consider the suggestions and ideas from the preschool practitioners' and parent/guardian focus group meetings, which will establish the meaning of PA for the two distinct stakeholder groups, their influences on this, and considerations for a future intervention. The Template for Intervention Description and Replication (TIDieR) framework was also used to set up the intervention component.

The design of the intervention will employ systematic review and qualitative phases to inform the quantitative, feasibility phase, followed by a further qualitative phase (stakeholders will be involved in the further refinement of the intervention to add richness and depth). Findings from the systematic review and qualitative work will inform the development of the IAAH intervention.

Intervention: This will be a feasibility study of a two-arm cluster-randomised controlled trial (RCT) and will consist of an intervention group and a control group with two data collection time points (i.e., baseline and post-intervention) to test the feasibility and efficacy of a 10-week "I'm an Active Hero (IAAH)" programme intervention with the aim of improving physical activity and decreasing sedentary behaviour of preschool children aged between 3 and 5 years in Taif City, Saudi Arabia.

Process evaluation: This will be a qualitative study including interviews and/or questionnaires with stakeholders (pre-school principals, teachers, classroom assistants, and parents/guardians) to determine the acceptability of the intervention from the participants' perspectives.

Inclusion Criteria:

• Children in the preschool years, ages 3 to 5, whose parents or guardians consent to their participation in the study
• An ambulatory individual who does not require physical assistance
• Children who able to follow verbal instructions

Exclusion Criteria:

• Children older than 5 years old
• Children for whom parental/caregiver consent is not provided
• Children with a concurrent medical condition that affects their ability to physically walk a certain distance or with health issues that might influence their participation in the intervention