title: The effect of an inclined landing surface on biomechanical variables during a jumping task.
abstract: BACKGROUND
  Professional dancers sustain a high number of injuries. Epidemiological studies have suggested that performing on inclined "raked" stages increases the likelihood of injury. However, no studies have examined if biomechanical differences exist between inclined and flat surfaces during functional tasks, such as landing from a jump. Such differences may provide a biomechanical rationale for differences in injury risk for raked stages.
  
  
  METHODS
  Eight professional dancers performed drop jumps from a 40cm platform on flat and inclined surfaces while forces, lower extremity kinematics, and electromyographic activity were collected in a controlled laboratory environment.
  
  
  RESULTS
  Dancers landed on the laterally inclined surface with significantly higher knee valgus (4 degrees ), peak knee flexion (9 degrees ), and medial-lateral ground reaction force (GRF) (13.4% body weight) compared to the flat condition. The posterior GRF was higher in the anterior inclined condition compared to the flat condition. In the anterior inclined condition, subjects landed with 1.4 degrees higher knee valgus, 4 degrees more plantarflexion at initial contact, and 3 degrees less dorsiflexion at the end of landing.
  
  
  CONCLUSIONS
  Biomechanical variables that have been suggested to contribute to injury in previous studies are increased in the inclined floor conditions. These findings provide a preliminary biomechanical rationale for differences in injury rates found in observational studies of raked stages.
authors.affiliation: Long Island University, Division of Physical Therapy, One University Plaza, Brooklyn, NY 11201, USA. mhagins@liu.edu
authors.forename: Marshall
authors.initials: M
authors.lastname: Hagins
authors.forename: Evangelos
authors.initials: E
authors.lastname: Pappas
authors.forename: Ian
authors.initials: I
authors.lastname: Kremenic
authors.forename: Karl F
authors.initials: KF
authors.lastname: Orishimo
authors.forename: Andrew
authors.initials: A
authors.lastname: Rundle
mesh_terms: D000328:Adult; D003615:Dancing / Q000502:physiology*; D005260:Female; D006801:Humans; D007719:Knee Joint / Q000502:physiology*; D008124:Locomotion / Q000502:physiology*; D008297:Male; D009119:Muscle Contraction / Q000502:physiology*; D016059:Range of Motion, Articular / Q000502:physiology*; D013314:Stress, Mechanical; D013647:Task Performance and Analysis