title: Changes in hip and ankle range of motion and hip muscle strength in 8-11 year old novice female ballet dancers and controls: a 12 month follow up study.
abstract: OBJECTIVE
  To evaluate in a 12 month longitudinal study changes in hip and ankle range of motion and hip muscle strength in young female novice ballet dancers.
  
  
  METHODS
  Fifty three of the original 77 (69%) female dancers aged 8-11 years and 40 of the original 49 (82%) controls returned for follow up measurements one year later. Supine right active hip external (ER) and internal (IR) rotation were measured using an inclinometer. A turnout protractor was used to assess standing active turnout range. Range of right weight bearing ankle dorsiflexion and calf muscle length were measured in a standing lunge position using an inclinometer. A manual muscle tester was used to assess right hip flexor, IR, ER, abductor and adductor strength.
  
  
  RESULTS
  The mean (SD) 12 month change in hip ER did not differ between dancers (11.7 (11.3)degrees) and controls (8.1 (17.6)degrees). Dancers gained 12.5 (13.5)degrees hip IR which was significantly greater than controls (0.5 (13.9)degrees). Greater IR change was associated with improved IR strength (r = 0.34, p<0.001). Dancers increased total turnout (12.0 (16.7)degrees) significantly more than controls (2.2 (20.0)degrees). There was no significant change in ankle dorsiflexion range in either group. Dancers and controls increased in all measures of hip muscle strength (p<0.001) and dancers achieved significantly greater gains in three out of five muscle groups (all, p<0.05).
  
  
  CONCLUSIONS
  Total hip range of motion increased in both ballet students and controls at this young age. However, ankle dorsiflexion did not, which is probably due to this movement being blocked by bony apposition, rather than soft tissue stretch. This has implications for ballet teachers, as it has long been accepted that this movement could be improved with training. Dancers had greater increases in hip strength after 12 months compared with controls in muscles specific for ballet, suggesting that hip strength can be trained at this young age. Whether these gains are permanent requires further study.
authors.affiliation: Centre for Sports Medicine Research and Education, School of Physiotherapy, University of Melbourne, Carlton, Victoria, Australia. k.bennell@physio.unimelb.edu.au
authors.forename: K L
authors.initials: KL
authors.lastname: Bennell
authors.forename: K M
authors.initials: KM
authors.lastname: Khan
authors.forename: B L
authors.initials: BL
authors.lastname: Matthews
authors.forename: C
authors.initials: C
authors.lastname: Singleton
mesh_terms: D000704:Analysis of Variance; D000843:Ankle Joint / Q000502:physiology*; D016022:Case-Control Studies; D002648:Child; D003615:Dancing / Q000502:physiology*; D005260:Female; D005500:Follow-Up Studies; D006621:Hip Joint / Q000502:physiology*; D006801:Humans; D008137:Longitudinal Studies; D018482:Muscle, Skeletal / Q000502:physiology; D016059:Range of Motion, Articular; D012399:Rotation; D016474:Weight-Bearing / Q000502:physiology