Individual responsiveness to a school-based karate intervention: An ancillary analysis of a randomized controlled trial

Introduction School-based sport interventions have shown beneficial effects on psychosocial functioning and academic performance in children. However, the inter-individual variability in response to these types of interventions remains unclear. We aimed to determine which children benefit most from a school-based sport intervention. Methods This is an ancillary analysis of a randomized controlled trial assessing the effects of a 1-year school-based karate intervention (versus "traditional" physical education lessons) in children (7-8 years) from twenty schools across five European countries. Outcomes included psychosocial functioning (Strengths and Difficulties Questionnaire [SDQ] for parents) and academic performance (grade point average). Only participants of the intervention group were included in the present ancillary analysis, and were categorized as responders or non-responders for the analyzed outcomes attending to whether improvements surpassed a minimal clinically important difference. Results About 388 children (187 girls) from the intervention group completed the study, of which 17% and 46% were considered responders for SDQ and academic performance, respectively. Responders for the SDQ presented higher SDQ scores (i.e., higher psychosocial difficulties) at baseline than non-responders (p < 0.001). Responders for academic performance were mostly males (p = 0.017), with an older age (p = 0.030), and with worse academic performance (p < 0.001) at baseline compared with non-responders, and tended to present higher SDQ scores (p = 0.055). Responders for one outcome obtained greater benefits from the intervention on the other outcome (e.g., responders for SDQ improved academic performance [p < 0.001] compared with non-responders). Conclusions A school-based sport intervention (karate) seems particularly effective for children with psychosocial difficulties and low academic performance.