LAUSR

Background The theory of planned behavior (TPB) model and its components have been applied to comprehend the adoption of physical activity along with informational and motivational parameters. Thus, the first aim of this exploratory study was to explore the evolution of children’s physical activity levels over a supervised physical activity program. The second aim was to describe the evolution of TPB measures, self-reported fitness and self-esteem in the physical domain to better understand children’s physical activity behavior over the course of the physical activity program. Methods A total of 16 children (8 boys and 8 girls) with cancer answered psychosocial questionnaires before and after a supervised physical activity program to explore the TPB measures, self-reported fitness, self-esteem in the physical domain and their daily physical activities. Results A significant increase of 13.8 min/day [95% CI (16.7; 10.8); p  < 0.0001; d  = 1.4] of daily MVLPA was observed between the time before (9.3 ± 9.1 min/day) and after (23.1 ± 10.8 min/day) the physical activity program. We found that the physical activity program positively impacted children’s TPB measures (mean in attitude, identity, facilitating factors, self-confidence and intention) and MVLPA levels. The TPB model explained 36.2% of the variance in MVLPA by injunctive norms after the physical activity program. Conclusion This study highlighted the need to provide children with physical activity support as soon as the cancer is diagnosed and showed that children’s physical activity behaviors were facilitated by familial support measured by injunctive norms.