Physical fitness has been positively related to academic performance in youth, yet this association has not been examined at a national level for cardiorespiratory fitness (CRF) and musculoskeletal fitness (MSF). PURPOSE: To examine the independent and combined associations of CRF and MSF with academic performance in Chilean 8th graders. METHODS: This cross-sectional study was based on a population-based, representative sample of 18,696 8th graders (median age=14 years) who were sampled in both the 2011 National Physical Education Survey and the 2011 National Academic Achievement Survey in Chile. Academic performance was assessed via four standardized tests: reading, math, natural science, and social sciences (max average score of all tests=404.0; min=132.8; mean=257.3). CRF was assessed with the 20-meter shuttle run test and MSF with standing broad jump. The independent associations of CRF and MSF with the mean of the four academic test scores were determined through multivariate linear regression. The combined influence of CRF and MSF on academic achievement was determined using ANCOVA with a three-level dependent variable: 1) unhealthy CRF and unhealthy MSF; 2) either unhealthy MSF or unhealthy CRF; 3) healthy MSF and healthy CRF. Both models controlled for body mass index, waist circumference, socioeconomic status, age, sex, and geographical location. Analyses were weighted and accounted for complex sampling design. RESULTS: MSF was positively associated with academic performance scores (beta=0.09, p<0.001), independent of CRF and other covariates, whereas CRF was not significantly associated with academic scores, after controlling for MSF and other covariates. Students with both unhealthy CRF and unhealthy MSF had poorer academic scores (adjusted mean score=253.2) than students with either unhealthy CRF or MSF (adjusted mean=256.9), who had yet poorer academic performance than students with healthy CRF and healthy MSF (adjusted mean=258.9; p for trend <0.001). CONCLUSIONS: Unhealthy MSF was associated with poorer academic scores in Chilean adolescents. When combined with unhealthy CRF, this effect intensified. Results are in line with previous studies finding a link between physical fitness and academic achievement in youth, this time at a nationally representative level. The findings may have implications for education policy in Chile.
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