title: Foot lengthening and shortening during gait: a parameter to investigate foot function?
abstract: BACKGROUND
  Based on the windlass mechanism theory of Hicks, the medial longitudinal arch (MLA) flattens during weight bearing. Simultaneously, foot lengthening is expected. However, changes in foot length during gait and the influence of walking speed has not been investigated yet.
  
  
  METHODS
  The foot length and MLA angle of 34 healthy subjects (18 males, 16 females) at 3 velocities (preferred, low (preferred -0.4 m/s) and fast (preferred +0.4 m/s) speed were investigated with a 3D motion analysis system (VICON(®)). The MLA angle was calculated as the angle between the second metatarsal head, the navicular tuberculum and the heel in the local sagittal plane. Foot length was calculated as the distance between the marker at the heel and the 2nd metatarsal head. A General Linear Model for repeated measures was used to indicate significant differences in MLA angle and foot length between different walking speeds.
  
  
  RESULTS
  The foot lengthened during the weight acceptance phase of gait and shortened during propulsion. With increased walking speed, the foot elongated less after heel strike and shortened more during push off. The MLA angle and foot length curve were similar, except between 50% and 80% of the stance phase in which the MLA increases whereas the foot length showed a slight decrease.
  
  
  CONCLUSIONS
  Foot length seems to represent the Hicks mechanism in the foot and the ability of the foot to bear weight. At higher speeds, the foot becomes relatively stiffer, presumably to act as a lever arm to provide extra propulsion.
authors.affiliation: Research Department, Sint Maartenskliniek, Nijmegen, The Netherlands. Electronic address: nstolwijk@yahoo.com.
authors.forename: N M
authors.initials: NM
authors.lastname: Stolwijk
authors.affiliation: Research Department, Sint Maartenskliniek, Nijmegen, The Netherlands.
authors.forename: K L M
authors.initials: KL
authors.lastname: Koenraadt
authors.affiliation: Research Department, Sint Maartenskliniek, Nijmegen, The Netherlands; Department of Orthopaedics, Sint Maartenskliniek, Nijmegen, The Netherlands.
authors.forename: J W K
authors.initials: JW
authors.lastname: Louwerens
authors.affiliation: Research Department, Sint Maartenskliniek, Nijmegen, The Netherlands.
authors.forename: D
authors.initials: D
authors.lastname: Grim
authors.affiliation: Research Department, Sint Maartenskliniek, Nijmegen, The Netherlands; Research Center for Movement Control and Neuroplasticity, Department of Biomedical Kinesiology, Katholieke Universiteit Leuven, Leuven, Belgium.
authors.forename: J
authors.initials: J
authors.lastname: Duysens
authors.affiliation: Research Department, Sint Maartenskliniek, Nijmegen, The Netherlands.
authors.forename: N L W
authors.initials: NL
authors.lastname: Keijsers
mesh_terms: D000328:Adult; D000368:Aged; D000843:Ankle Joint / Q000502:physiology; D001696:Biomechanical Phenomena; D005260:Female; D005528:Foot / Q000502:physiology*; D005684:Gait / Q000502:physiology*; D006365:Heel / Q000502:physiology; D006801:Humans; D008297:Male; D008875:Middle Aged; D011187:Posture / Q000502:physiology*; D016138:Walking / Q000502:physiology; D016474:Weight-Bearing / Q000502:physiology*; D055815:Young Adult
keywords: Foot; Foot length; Kinematics; Medial longitudinal arch; Walking speed