title: The influence of heel height on vertical ground reaction force during landing tasks in recreationally active and athletic collegiate females.
abstract: OBJECTIVE
  To determine if heel height alters vertical ground reaction forces (vGRF) when landing from a forward hop or drop landing.
  
  
  BACKGROUND
  Increased vGRF 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 athletic shoe. Using a force plate, peak vGRF at landing was examined. Repeated measures ANOVAs were used to determine the influence of heel height on the dependent measures.
  
  
  RESULTS
  Forward hop task- Peak vGRF (normalized for body mass) with 0 mm, 12 mm, and 24 mm lifts were 2.613±0.498, 2.616±0.497 and 2.495±0.518% BW, respectively. Significant differences were noted between 0 and 24 mm lift (p<.001) and 12 and 24 mm lifts (p=.004), but not between the 0 and 12 mm conditions (p=.927). Jump-landing task- No significant differences were found in peak vGRF (p=.192) between any of the heel lift conditions.
  
  
  CONCLUSIONS
  The addition of a 24 mm heel lift to the bottom of a sneaker significantly alters peak vGRF upon landing from a unilateral forward hop but not from a jumping maneuver.
authors: Associate Professor, Slippery Rock University, School of Physical Therapy, Slippery Rock, PA.
authors: Kelly M
authors: KM
authors: Lindenberg
authors: Christopher R
authors: CR
authors: Carcia
keywords: ACL; ground reaction force; heel lift; landing