title: Swimming and bone: Is low bone mass due to hypogravity alone or does other physical activity influence it?
abstract: Swimming during adolescence has shown neutral or even negative effects on bone mass. Nevertheless, it is still unknown if these effects are due to swimming or to other factors, such as sedentary behaviors.
  
  
  BACKGROUND
  Three objectives were described (1) to measure objective physical activity (PA) additional to swimming performed by adolescent swimmers (SWI) and compare it to that performed by normo-active controls (CG), (2) to describe the relationship between objectively measured PA and bone mass, and (3) to compare bone mass of swimmers that meet the World Health Organization PA guidelines (active) WHO and those that do not (inactive).
  
  
  METHODS
  A total of 71 SWI (33 females) and 41 CG (17 females) wore an accelerometer for at least 4 days. PA was expressed as the amount of time (minutes/day) in each intensity [sedentary/light/moderate or vigorous (VPA), and the sum of moderate and vigorous (MVPA)]. Using the cutoff points proposed by Vanhelst et al. SWI were classified as active or inactive according to whether they reached 60 min of weight-bearing MVPA per day or not. Bone mineral density (BMD) was measured by dual energy X-ray absorptiometry, and bone strength values were calculated with peripheral quantitative computed tomography. Differences in PA intensities were calculated between SWI and CG. The relation of VPA to bone mass was studied in the SWI.
  
  
  RESULTS
  Male-SWI spend less time in VPA and MVPA than male-GC, which partly explains the lower BMD values in SWI than CG.
  
  
  CONCLUSIONS
  Swimming may displace weight-bearing VPA with serious implications on bone health.
authors.affiliation: GENUD "Growth, Exercise, NUtrition and Development" Research Group, Grupo GENUD, University of Zaragoza, Edificio SAI 2ª planta, Zaragoza, Spain.|Faculty of Health and Sport Sciences (FCSD), Department of Physiatry and Nursing, University of Zaragoza, Ronda Misericordia 5, 22001, Huesca, Spain.
authors.forename: A
authors.initials: A
authors.lastname: Gómez-Bruton
authors.affiliation: GENUD "Growth, Exercise, NUtrition and Development" Research Group, Grupo GENUD, University of Zaragoza, Edificio SAI 2ª planta, Zaragoza, Spain.|Department of Sport and Exercise Science, Aberystwyth University, Ceredigion, UK.
authors.forename: A
authors.initials: A
authors.lastname: González-Agüero
authors.affiliation: GENUD "Growth, Exercise, NUtrition and Development" Research Group, Grupo GENUD, University of Zaragoza, Edificio SAI 2ª planta, Zaragoza, Spain.|Centro Universitario de la Defensa, Zaragoza, Spain.
authors.forename: A
authors.initials: A
authors.lastname: Gómez-Cabello
authors.affiliation: GENUD "Growth, Exercise, NUtrition and Development" Research Group, Grupo GENUD, University of Zaragoza, Edificio SAI 2ª planta, Zaragoza, Spain.|Faculty of Health and Sport Sciences (FCSD), Department of Physiatry and Nursing, University of Zaragoza, Ronda Misericordia 5, 22001, Huesca, Spain.
authors.forename: A
authors.initials: A
authors.lastname: Matute-Llorente
authors.affiliation: GENUD "Growth, Exercise, NUtrition and Development" Research Group, Grupo GENUD, University of Zaragoza, Edificio SAI 2ª planta, Zaragoza, Spain.|Faculty of Health and Sport Sciences (FCSD), Department of Physiatry and Nursing, University of Zaragoza, Ronda Misericordia 5, 22001, Huesca, Spain.
authors.forename: J A
authors.initials: JA
authors.lastname: Casajús
authors.affiliation: GENUD "Growth, Exercise, NUtrition and Development" Research Group, Grupo GENUD, University of Zaragoza, Edificio SAI 2ª planta, Zaragoza, Spain. gervicen@unizar.es.|Faculty of Health and Sport Sciences (FCSD), Department of Physiatry and Nursing, University of Zaragoza, Ronda Misericordia 5, 22001, Huesca, Spain. gervicen@unizar.es.
authors.forename: G
authors.initials: G
authors.lastname: Vicente-Rodríguez
mesh_terms: D015502:Absorptiometry, Photon / Q000379:methods; D061725:Accelerometry / Q000379:methods; D000293:Adolescent; D015519:Bone Density / Q000502:physiology*; D016022:Case-Control Studies; D002648:Child; D015444:Exercise / Q000502:physiology; D005260:Female; D006801:Humans; D018472:Hypogravity / Q000009:adverse effects*; D008297:Male; D011884:Radius / Q000502:physiology; D012737:Sex Factors; D013550:Swimming / Q000502:physiology*; D013977:Tibia / Q000502:physiology; D014057:Tomography, X-Ray Computed / Q000379:methods; D016474:Weight-Bearing / Q000502:physiology
keywords: Accelerometry; Bone mass; DXA; Swimming; pQCT