The main purpose of this doctoral thesis is to determine in which way are level of physical activity (PA), adiposity, and injury related to the quality of movement patterns among adolescent population. Within this doctoral thesis, there are three distinct studies with related research questions and aims (Study 1, Study 2, and Study 3). Study 1 examined relationship between functional movement and PA in an urban adolescent population, while study 2 strive to identify association between adiposity and quality of movement patterns among the adolescent population. Finally, in Study 3, machine learning (ML) was used to predict injuries among adolescents by functional movement testing. Participants in all three studies were part of the Physical Activity in Adolescence Longitudinal Study (CRO-PALS) cohort. In Study 1 we included 725 adolescents (aged between 16 and 17 years) from CRO-PALS cohort. Movement quality was evaluated via Functional Movement ScreenTM (FMSTM) while PA was assessed with the School Health Action, Planning and Evaluation System (SHAPES) questionnaire. From SHAPES questionnaire, vigorous PA (VPA) and moderate-to-vigorous PA (MVPA) was calculated. Confounders included chronological age, body fat and socioeconomic status (SES). Results of Study 1 indicated that after adjusting for age, body fat and SES, both VPA and MVPA showed minor but significant effects on total FMS score among girls (β=0.011, p=0.001, β=0.005, p=0.006, respectively), but not in boys (β=0.004, p=0.158; β=0.000, p=0.780). Regarding PA type, volleyball and dance improved total FMS score (β=1.003, p=0.071; β=0.972, p=0.043, respectively), while football was associated with lower FMS score (β=-0.569, p=0.118). Conclusively, results of Study 1 showed that PA level is positively associated with the functional movement in adolescent girls, but not in boys, where the type of PA moderates these associations. Because girls are more engaged in aesthetic sports activities that improve functional movement, and unlike boys are in the final stages of maturation, this could affect sexual dimorphism in the quality of movement among the adolescent population. In Study 2 participants were 652 urban adolescents (aged between 16 and 17 years). Body mass index (BMI), a sum of four skinfolds (S4S), waist and hip circumference were measured, and movement quality (i.e. functional movement – FM) was assessed via FMSTM. Furthermore, total FMSTM screen was indicator of FM with the
composite score ranged from 7 to 21, with higher score indicating better FM. Multilevel analysis was employed to determine the relationship between different predictors and total FMS score. Results of the Study 2 demonstrate that, in boys, after controlling for age, MVPA, and SES, total FMS score was inversely associated with BMI (β=-0.18, p<0.0001), S4S (β=-0.04, p<0.0001), waist circumference (β=-0.08, p<0.0001), and hip circumference (β=-0.09, p<0.0001). However, among girls, in adjusted models, total FMS score was inversely associated only with S4S (β=-0.03, p<0.0001), while BMI (β=-0.05, p=0.23), waist circumference (β=-0.04, p=0.06), and hip circumference (β=-0.01, p=0.70) failed to reach statistical significance. Findings of Study 2 point out that the association between adiposity and FM in adolescence is sex-specific, suggesting that boys with overweight and obesity could be more prone to develop dysfunctional movement patterns. Therefore, exercise interventions directed toward correcting dysfunctional movement patterns should be sex-specific, targeting more boys with overweight and obesity rather than adolescent girls with excess weight. Analyses for the Study 3 were based on nonathletic (n=364) and athletic (n=192) subgroups of the cohort (16–17 years). Sex, age, BMI, body fatness, MVPA, training hours per week, FMS, and SES were assessed at baseline. A year later, data on injury occurrence were collected. The optimal cut-point of the total FMS score for predicting injury was calculated using receiver operating characteristic curve. These predictors were included in ML analyses with calculated metrics: area under the curve (AUC), sensitivity, specificity, and odds ratio (95% confidence interval [CI]). Results of the receiver operating characteristic curve analyses with associated criterium of total FMS score >12 showed AUC of 0.54 (95% CI: 0.48–0.59) and 0.56 (95% CI: 0.47–0.63), for the nonathletic and athletic youth, respectively. However, in the nonathletic subgroup, ML showed that the Naïve Bayes exhibited highest AUC (0.58), whereas in the athletic group, logistic regression was demonstrated as the model with the best predictive accuracy (AUC: 0.62). In both subgroups, with given predictors: sex, age, BMI, body fat percentage, MVPA, training hours per week, SES, and total FMS score, ML can give a more accurate prediction then FMS alone. Results of the Study 3 indicate that nonathletic boys who have lower-body fat could be more prone to suffer from injury incidence, whereas among athletic subjects, boys who spend more time training are at a higher risk of being injured. Conclusively, total FMS cut-off scores for each
subgroup did not successfully discriminate those who suffered from those who did not suffer from injury, and, therefore, this study does not support FMS as an injury prediction tool.