Decreased external skeletal robustness due to reduced physical activity?

Abstract

Objectives: Childhood obesity is a global problem, e.g., due to physical inactivity. External skeletal robustness (Frame-Index) has decreased in German schoolchildren. An association between Frame-Index and physical activity was assumed. Further often body mass index (BMI) is analyzed without reference to bone structure. Therefore, we analyze relationships between Frame-Index, BMI, % body fat, and physical activity.

Methods: In a cross-sectional study, 691 German children aged 6-10 years were investigated. BMI, % body fat, Frame-Index, total steps p.w., sports club rate p.w., training time p.d., and TV-time p.d. were determined.

Results: Total steps (P < 0.001), BMI (P < 0.001), and % body fat (P = 0.024) are positively linked to Frame-Index. Total steps (P < 0.001), sports club rate (P = 0.001), and training time (P < 0.001) are negatively associated with % body fat. Total steps (P = 0.017) are negatively linked to BMI. TV-time is positively related to BMI (P < 0.001) and % body fat (P < 0.001). % Body fat is affected by age (P < 0.001), sex (P = 0.028), and total steps (P = 0.002). BMI is influenced by age (P < 0.001), and Frame-Index by sex (P < 0.001) and total steps (P = 0.029). Principal component analysis indicates an association between BMI and TV-time and Frame-Index and total steps.

Conclusions: We demonstrate an association between external skeletal robustness and physical activity, which is not captured by in BMI measurements. Children should be physically active in order to maintain skeletal robustness.