title: The influence of heel height on sagittal plane knee kinematics during landing tasks in recreationally active and athletic collegiate females.
abstract: OBJECTIVE
  To determine if heel height alters sagittal plane knee kinematics when landing from a forward hop or drop landing.
  
  
  BACKGROUND
  Knee angles close to extension during landing are theorized to increase ACL injury risk in female athletes.
  
  
  METHODS
  Fifty collegiate females performed two single-limb landing tasks while wearing heel lifts of three different sizes (0, 12 & 24 mm) attached to the bottom of a sneaker. Using an electrogoniometer, sagittal plane kinematics (initial contact [KA(IC)], peak flexion [KA(Peak)], and rate of excursion [RE]) were examined. Repeated measures ANOVAs were used to determine the influence of heel height on the dependent measures.
  
  
  RESULTS
  Forward hop task- KA(IC) with 0 mm, 12 mm, and 24 mm lifts were 8.88±6.5, 9.38±5.8 and 11.28±7.0, respectively. Significant differences were noted between 0 and 24 mm lift (p<.001) and 12 and 24 mm lifts (p=.003), but not between the 0 and 12 mm conditions (p=.423). KA(Peak) with 0 mm, 12 mm, and 24 mm lifts were 47.08±10.9, 48.18±10.3 and 48.88±9.7, respectively. A significant difference was noted between 0 and 24 mm lift (p=.004), but not between the 0 and 12 mm or 12 and 24 mm conditions (p=.071 and p=.282, respectively). The RE decreased significantly from 2128/sec±52 with the 12 mm lift to 1958/sec±55 with the 24 mm lift (p=.004). RE did not differ from 0 to 12 or 0 to 24 mm lift conditions (p=.351 and p=.086, respectively). Jump-landing task- No significant differences were found in KA(IC) (p=.531), KA(Peak) (p=.741), or the RE (p=.190) between any of the heel lift conditions.
  
  
  CONCLUSIONS
  The addition of a 24 mm heel lift to the bottom of a sneaker significantly alters sagittal plane knee kinematics upon landing from a unilateral forward hop but not from a drop jump.
authors: Kelly M
authors: KM
authors: Lindenberg
authors: Christopher R
authors: CR
authors: Carcia
authors: Amy L
authors: AL
authors: Phelps
authors: Robroy L
authors: RL
authors: Martin
authors: Anne M
authors: AM
authors: Burrows