title: Less physically active children are shorter.
abstract: BACKGROUND
  Current concepts of linear growth include genetic, endocrine and nutritional factors. Limited and controversial results exist regarding the effect of physical activity (PA) on linear growth. In 2009, we showed that PA promotes foot length in hypoactive children with Prader-Willi-Syndrome. In the present study we tested the hypothesis that PA related epiphyseal loading has a positive modulating effect on linear growth in healthy school children.
  
  
  METHODS
  In 99 healthy schoolchildren, we measured height, foot length and PA by tri-axial accelerometry. PA related epiphyseal loading was expressed as the product between mass (body weight) and acceleration (vector magnitude). Correlation between height, foot length and PA were calculated taking into account co-variables age, sex, parental height, lean and fat mass measured by DEXA.
  
  
  RESULTS
  Height SDS (P<0.015, r=0.245) as well as foot length SDS (P<0.001, r=0.363) correlated with PA. Multiple linear regression models showed that muscle mass expressed by lean body mass has higher correlation with PA, height SDS and foot length SDS than fat mass.
  
  
  CONCLUSIONS
  This study shows that physically less active children are shorter and have shorter feet. In analogy to the "muscle bone unit", we propose a "muscle epiphyseal unit" which regulates local bone growth as long as epiphyseal plates are still open.
authors.affiliation: Center for Pediatric Endocrinology Zürich (PEZZ), Zurich, Switzerland.
authors.forename: Udo
authors.initials: U
authors.lastname: Meinhardt
authors.affiliation: Center for Pediatric Endocrinology Zürich (PEZZ), Zurich, Switzerland.
authors.forename: Fabienne
authors.initials: F
authors.lastname: Witassek
authors.affiliation: Center for Pediatric Endocrinology Zürich (PEZZ), Zurich, Switzerland.
authors.forename: Renato
authors.initials: R
authors.lastname: Petrò
authors.affiliation: Center for Pediatric Endocrinology Zürich (PEZZ), Zurich, Switzerland.
authors.forename: Christiane
authors.initials: C
authors.lastname: Fritz
authors.affiliation: Center for Pediatric Endocrinology Zürich (PEZZ), Zurich, Switzerland - urs.eiholzer@pezz.ch.
authors.forename: Urs
authors.initials: U
authors.lastname: Eiholzer
mesh_terms: D015502:Absorptiometry, Photon; D061725:Accelerometry; D000293:Adolescent; D001827:Body Height / Q000502:physiology*; D001835:Body Weight / Q000502:physiology*; D002648:Child; D003430:Cross-Sectional Studies; D004838:Epiphyses / Q000502:physiology*; D015444:Exercise / Q000502:physiology*; D005260:Female; D005528:Foot / Q000033:anatomy & histology; D006801:Humans; D008297:Male