Sex and age correlations of reported and estimated physical fitness in adolescents

The main purpose of the study was to explore sex and age specific correlations between self-reported and estimated physical fitness. In this cross-sectional study, we recruited 1 036 secondary-school students (55.3% girls). Self-reported physical fitness was assessed on a 10-point scale, with a higher score indicating better physical fitness. We measured waist circumference, sit-ups in 1 minute, standing long jump and sit-and-reach test and calculated z -scores to obtain objective physical fitness index. Boys performed better in sit-ups in 1 minute and standing long jump tests and had higher waist circumference values. Girls performed better in sit-and-reach test. Overall, boys had higher physical fitness z -score values, compared to girls. Younger boys had better physical fitness perception ( r 1st grade = 0.61, p <0.001), compared to older ones ( r = 0.40–0.50, p <0.001). In girls, correlation coefficient was the highest in the 3 rd grade ( r = 0.46, p <0.001), followed by the 2 nd grade ( r = 0.43, p <0.001), the 1 st grade ( r = 0.41, p <0.001) and the 4 th grade ( r = 0.37, p <0.001). Our study shows moderate sex and age specific correlation between self-reported and estimated physical fitness in a large sample of adolescents.