title: Muscle function in Turner syndrome: normal force but decreased power.
abstract: OBJECTIVE
  Although hypogonadism and SHOX gene haploinsufficiency likely cause the decreased bone mineral density and increased fracture rate associated with Turner syndrome (TS), the exact mechanism remains unclear. We tested the hypothesis that muscle dysfunction in patients with TS contributes to increased fracture risk. The secondary aim was to determine whether menarche, hormone therapy duration, positive fracture history and genotype influence muscle function parameters in patients with TS.
  
  
  METHODS
  A cross-sectional study was conducted in a single university hospital referral centre between March 2012 and October 2013.
  
  
  METHODS
  Sixty patients with TS (mean age of 13·7 ± 4·5 years) were compared to the control group of 432 healthy girls.
  
  
  METHODS
  A Leonardo Mechanograph(®) Ground Reaction Force Platform was used to assess muscle force (Fmax ) by the multiple one-legged hopping test and muscle power (Pmax ) by the single two-legged jump test.
  
  
  RESULTS
  While the Fmax was normal (mean weight-specific Z-score of 0·11 ± 0·77, P = 0·27), the Pmax was decreased in patients with TS (Z-score of -0·93 ± 1·5, P < 0·001) compared with healthy controls. The muscle function parameters were not significantly influenced by menarcheal stage, hormone therapy duration, fracture history or genotype (linear regression adjusted for age, weight and height; P > 0·05 for all).
  
  
  CONCLUSIONS
  Fmax , a principal determinant of bone strength, is normal in patients with TS. Previously described changes in bone quality and structure in TS are thus not likely related to inadequate mechanical loading but rather represent a primary bone deficit. A decreased Pmax indicates impaired muscle coordination in patients with TS.
authors.affiliation: Department of Paediatrics, 2nd Faculty of Medicine, Charles University in Prague and Motol University Hospital, Prague, Czech Republic.
authors.forename: Ondrej
authors.initials: O
authors.lastname: Soucek
authors.forename: Jan
authors.initials: J
authors.lastname: Lebl
authors.forename: Jana
authors.initials: J
authors.lastname: Matyskova
authors.forename: Marta
authors.initials: M
authors.lastname: Snajderova
authors.forename: Stanislava
authors.initials: S
authors.lastname: Kolouskova
authors.forename: Stepanka
authors.initials: S
authors.lastname: Pruhova
authors.forename: Zdenek
authors.initials: Z
authors.lastname: Hlavka
authors.forename: Zdenek
authors.initials: Z
authors.lastname: Sumnik
mesh_terms: D000293:Adolescent; D000328:Adult; D015519:Bone Density / Q000502:physiology; D001842:Bone and Bones / Q000503:physiopathology; D002648:Child; D002675:Child, Preschool; D003430:Cross-Sectional Studies; D005080:Exercise Test; D005260:Female; D006801:Humans; D009119:Muscle Contraction / Q000502:physiology*; D053580:Muscle Strength / Q000502:physiology*; D009135:Muscular Diseases / Q000209:etiology / Q000503:physiopathology*; D014424:Turner Syndrome / Q000150:complications / Q000503:physiopathology*; D055815:Young Adult