title: Decreased external skeletal robustness due to reduced physical activity?
abstract: OBJECTIVE
  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.
authors.affiliation: Human Biology, Institute of Biochemistry and Biology, University of Potsdam, Potsdam, Germany. katrin.rietsch@uni-potsdam.de
authors.forename: Katrin
authors.initials: K
authors.lastname: Rietsch
authors.forename: Jana A
authors.initials: JA
authors.lastname: Eccard
authors.forename: Christiane
authors.initials: C
authors.lastname: Scheffler
mesh_terms: D050154:Adiposity; D001823:Body Composition; D015992:Body Mass Index; D001842:Bone and Bones / Q000502:physiology*; D002648:Child; D003430:Cross-Sectional Studies; D015444:Exercise / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D012307:Risk Factors; D057185:Sedentary Behavior