Background/Purpose Increases in body mass index have been shown to interfere with the control of standing posture. A long standing, fundamental body scale to performance relation holds that strength increases proportionally with increased body size; however, this may be mediated by obesity and fitness-related variables. This study investigated the influence of selected body scale, body composition, mechanical and strength variables as predictors of postural motion in obese and non-obese adolescents.
Method 125 healthy adolescents (65 boys, 60 girls) with a wide range of BMI (13.8 to 31.0 kg/m2) performed a battery of tests that included body composition, anthropometry, muscular strength and postural control. Multiple measures of postural motion variability were derived for analysis with body scale, mechanical and strength variables separately for boys and girls.
Analysis/Results BMI, height and weight whether considered separately or collectively were poor and/or inconsistent predictors of variability in all three posture tasks. However, the ratio of strength to whole body moment of inertia showed the highest positive correlation to most postural variability measures in both boys and girls and these effects were strongest in the less stable tasks of single leg and recovery of stance.
Conclusions The findings show that obesity differentially increases postural motion variability of adolescents particularly in less stable postural tasks. Our findings support the hypothesis that obesity leads to a lower strength to mechanical constraint ratio that compromises the robustness of the strength to body scale relation and its relation to movement and postural control.