Background: Evidence suggests that social support impacts on participation in sport or physical activity (PA), and is associated with health benefits, although the link is complex and not well understood. The study aim was to examine whether participation in organized sports is related to body composition, physical fitness, and social correlates for PA. Methods: Cross-sectional data on 238 adolescents (90 boys and 148 girls), mean age 14.9 ± 0.8 years, who were participants in the Physical Activity and Health Longitudinal Study, were collected. The participants were divided into two groups: sport participation (SP) and non-sport participation (NSP). Height, weight, and triceps and subscapular skinfolds were assessed according to standard procedures. Weight (kg) and height (m²) were used to calculate body mass index (BMI), and skinfolds were used to calculate body fat percentage. The European Test of Physical Fitness (EUROFIT) battery of tests was used to assess physical fitness. The standardized International Physical Activity Questionnaire Short Form and Social Support for PA questionnaires were used to obtain information on PA and social correlates for PA, respectively. Participants were asked to choose between participation and non-participation in sport. Results: The SP group had lower BMI component values (p = 0.011, d = 0.52 for percentage body fat (%BF); p = 0.011, d = 0.53 for sum of skinfolds (∑SKF) obtained higher physical fitness scores in selected items (p = 0.003, d = 0.64 for sit ups (SUP); p < 0.000, d = 0.96 for maximal oxygen consumption VO₂max) and received higher social support (p < 0.001, d = 0.86 for social support (SS)), than the NSP group. The social support received by those participating in sport correlated positively with most fitness components (p = 0.013, r² = 18% for bent arm hang (BAH); p = 0.000, r² = 12% for sit ups (SUP); p = 0.000, r² = 17% for VO₂max). Physical fitness components were negatively associated with most body composition components for both groups. Conclusions: The results provide a better understanding of sport participation in organized sports-related, body composition-related and physical fitness-related associations with changes in social support received by adolescents and may contribute to the development of more accurate promotive strategies to increase children's and adolescents' engagement in sport and PA.
Keywords: adolescents; body composition; physical activity; physical fitness; social support; sport.