Skeletal and muscular robustness and physical fitness of Polish children and adolescents (3-18 years) with normal weight and overweight/obesity.

Individuals with excess body mass are usually characterised by a more robust skeleton and greater muscle mass than their leaner counterparts. The aim of this study was to evaluate the skeletal robustness, bone and muscle mass as well as physical fitness of Polish children and adolescents with and without excess body mass. The study group consisted of 3292 individuals (1705 girls and 1587 boys). Body height, mass, triceps skinfold, humerus, femur and bistyloid breadths, as well as thigh and mid-upper arm circumferences, were measured. BMI, Frame Index, bone and muscle mass were calculated. Results of handgrip strength, standing broad jump, sit-and-reach and shuttle-run tests were obtained. Participants were categorised as normal-weight or with overweight/obesity according to Cole's cut-offs. Statistical differences were calculated using two-way ANOVA (independent variables: age category, BMI group; dependent variable: analysed characteristic). Individuals in the overweight/obese category had larger absolute bone and muscle mass, as well as values of associated measurements and results of handgrip strength than their leaner counterparts. The normal-weight individuals had a greater relative bone, muscle mass and achieved better results in most fitness tests, including relative dynamometric force. In conclusion, individuals in the overweight/obese category were characterised by an increased absolute mass of bone and muscle tissue, as well as greater values of associated measurements, in comparison to their leaner counterparts. However, those advantages did not translate into better physical fitness. It may be associated with the fact that in proportion to the total body weight, bone and muscle mass were greater among participants in the normal-weight category.