RESUMO
BACKGROUND: Affect and physical fitness play an important role in psychological and physical health; however, the association between those variables in youth remains unknown. The aim of the present study was to examine the influence of physical fitness on positive and negative affect in Spanish children and adolescents. METHOD: Healthy young Spanish people (n = 1,490) were recruited for the present study: 542 children (n = 272 girls; mean age 9.6 years) and 948 adolescents (n = 454 girls; mean age 14.1 years) with complete baseline data on health-related fitness tests (20 m shuttle run test, 4 × 10 m test, muscular fitness index, and physical fitness index), and positive and negative affect (Positive and Negative Affect Schedule). RESULTS: Higher performance on physical fitness components was associated with positive affect (ß = -0.176-0.118, all P < 0.05). There was no association between all physical fitness components and negative affect (ß = -0.100-0.15, all P > 0.05). There were differences on positive affect between the lowest and the highest quartile of the physical fitness index in boys (P = 0.037, Cohen's d 0.60) and girls (P = 0.004, Cohen's d = 0.69), and between the lowest and the highest quartile of muscular fitness index in girls (P < 0.001, Cohen's d = 0.76). CONCLUSIONS: Promoting physical activity during the school years, including strength exercises to increase muscular fitness, could improve positive affect levels and thus psychological health.