title: Bone mineral density differences between adolescent dancers and non-exercising adolescent females.
abstract: OBJECTIVE
  To compare the bone mineral density (BMD) of the axial and appendicular skeleton between regularly exercising collegiate dancers and age matched non-exercising young females between the age of 17 and 19 to assess the impact of weight-bearing exercises and menstrual status on BMD.
  
  
  METHODS
  Prospective observational cohort.
  
  
  METHODS
  Sports clinic in a collegiate school of dance and a hospital-based adolescent clinic.
  
  
  METHODS
  The adolescent dancers consisted of full-time collegiate dance students from a tertiary Performing Arts Institute (n = 35). The non-exercising controls consisted of eumenorrhoeic patients of the same age presenting to the Adolescent Clinic (n = 35).
  
  
  METHODS
  All subjects had a full hormonal profile, bio-impedance estimation of body fat, and dual energy X-ray absorptiometry and quantitative peripheral CT scans (pQCT) to determine bone density.
  
  
  METHODS
  Comparison of the mean bone mineral density in the axial and appendicular skeleton between the two groups.
  
  
  RESULTS
  The incidence of oligo/amenorrhoea in the dancers was 20%. The lumbar spine BMD (1.006 g/cm(2) vs. 0.938, P = 0.048) and hip BMD (neck of femur 0.978 g/cm(2) vs. 0.838, P < 0.001; Ward's triangle 0.816 g/cm(2) vs. 0.720, P = 0.003; trochanter 0.777 g/cm(2) vs. 0.682; P < 0.001) were significantly higher in the eumenorrhoeic dancers as compared to controls. The radial BMD as measured by pQCT did not differ between the two groups, but the core trabecular tibial BMD was also higher in the dancers (321 mg/cm(3) vs. 286, P = 0.006). When only oligo/amenorrhoeic dancers (n = 7) were compared with the controls, the same differences in BMD values were no longer observed.
  
  
  CONCLUSIONS
  Young women undergoing regular intensive weight-bearing exercises as in the collegiate dancers here studied have higher BMD in the axial and appendicular skeleton as compared to non-exercising females of the same age if they remain eumenorrhoeic during their training. This advantage was apparently lost when they developed oligo/amenorrhoea.
authors.affiliation: Department of Obstetrics & Gynaecology, United Christian Hospital, Kwun Tong, Kowloon, Hong Kong. towkw@ha.org.hk
authors.forename: William W K
authors.initials: WW
authors.lastname: To
authors.forename: Margaret W N
authors.initials: MW
authors.lastname: Wong
authors.forename: Ivy Y L
authors.initials: IY
authors.lastname: Lam
mesh_terms: D015502:Absorptiometry, Photon; D000293:Adolescent; D001835:Body Weight; D015519:Bone Density / Q000502:physiology*; D016022:Case-Control Studies; D002681:China; D003615:Dancing / Q000502:physiology*; D005260:Female; D006801:Humans; D008599:Menstruation Disturbances / Q000503:physiopathology; D011446:Prospective Studies; D018709:Statistics, Nonparametric; D014057:Tomography, X-Ray Computed; D016474:Weight-Bearing / Q000502:physiology