A randomized study of CrossFit Kids for fostering fitness and academic outcomes in middle school students

Within the context of school-based physical education (PE), a strength and conditioning program called CrossFit Kids (CFK) has emerged as a potential intervention for positively impacting students. The purpose of this study was to evaluate through a randomized-controlled trial how academic and health-related fitness outcomes differed for middle school students (age = 12.73; 55.3 % male) who participated in a school-based CFK program (n=72) as compared to a group of students who participated in PE class (n=72). Questionnaire data were collected twice across the 9-month academic year and combined with FitnessGram and grade data. Students in both the intervention and comparison groups increased in health-related fitness outcomes (all p values < .017), and there was a significant treatment group by time interaction on school-reported grades [F(1, 124) = 7.270, p = .008, η_P^2 = .055]. Significant gender by time interaction effects were found for the relationship between CFK or PE participation and health-related fitness outcomes, but there were no significant interaction effects by gender on academic outcomes. Because developmental outcomes are conditional and result from the coaction of many factors, the findings suggest that some elements of CFK might be beneficial to build skills yet disadvantageous to academic outcomes.