title: Medial and Lateral Heel Whips: Prevalence and Characteristics in Recreational Runners.
abstract: OBJECTIVE
  To investigate the prevalence and characteristics of recreational runners with medial and lateral heel whips.
  
  
  METHODS
  Observational cohort study.
  
  
  METHODS
  Clinical research laboratory.
  
  
  METHODS
  A total of 256 recreationally active runners and joggers participated.
  
  
  METHODS
  High-definition video was acquired from a posterior view while runners ran at a self-selected pace on a treadmill. Heel whips, defined as the medial or lateral rotation of the foot in the transverse plane during initial swing, were measured with Dartfish software. Subjects were stratified by direction (medial and lateral) and severity (W_5-10 = 5-10 degrees; W_10+ = >10 degrees) of heel whip. Body mass index and gender comparisons, as well as measurement reliability, also were explored.
  
  
  RESULTS
  Mean heel whip angle across runners was 0.4 degrees (medial) with a standard deviation of 9.2 degrees. Of the 512 feet analyzed, 274 (54%) demonstrated a 5 degree whip or greater. There was a similar number of medial and lateral heel whips observed (27% each). Female runners were twice as likely to demonstrate a lateral heel whip of greater than 8.9 degrees. Overweight runners had more medially directed whips when compared with normal and underweight runners.
  
  
  CONCLUSIONS
  More than half of the recreational runners studied were observed to have a medial or lateral heel whip of greater than 5 degrees. These data reveal the age, body mass index, and gender distribution of recreational runners with and without heel whips.
authors.affiliation: Department of Physical Therapy and Rehabilitation Science, University of California, San Francisco, 185 Berry Street, Suite 350, San Francisco, CA 94107; and Department of Orthopaedic Surgery, University of California, San Francisco, San Francisco, CA.
authors.forename: Richard B
authors.initials: RB
authors.lastname: Souza
authors.affiliation: Department of Orthopaedic Surgery, University of California, San Francisco, San Francisco, CA.
authors.forename: Nicolas
authors.initials: N
authors.lastname: Hatamiya
authors.affiliation: Department of Physical Therapy and Rehabilitation Science, University of California, San Francisco, San Francisco, CA.
authors.forename: Carly
authors.initials: C
authors.lastname: Martin
authors.affiliation: Department of Physical Therapy and Rehabilitation Science, University of California, San Francisco, San Francisco, CA.
authors.forename: Andrew
authors.initials: A
authors.lastname: Aramaki
authors.affiliation: Department of Physical Therapy and Rehabilitation Science, University of California, San Francisco, San Francisco, CA.
authors.forename: Brian
authors.initials: B
authors.lastname: Martinelli
authors.affiliation: Department of Physical Therapy and Rehabilitation Science, University of California, San Francisco, San Francisco, CA.
authors.forename: Jamie
authors.initials: J
authors.lastname: Wong
authors.affiliation: Department of Orthopaedic Surgery, University of California, San Francisco, San Francisco, CA.
authors.forename: Anthony
authors.initials: A
authors.lastname: Luke
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001696:Biomechanical Phenomena; D005260:Female; D006365:Heel / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D011998:Recreation / Q000502:physiology*; D012016:Reference Values; D015203:Reproducibility of Results; D012189:Retrospective Studies; D012420:Running / Q000502:physiology*; D055815:Young Adult