title: [The effect of similar speed's walking and functional classification of foot contact on variability of the vertical ground reaction force].
abstract: BACKGROUND
  The variability of the normal ground reaction force (F(z)) is a restrictive factor for the clinical analyse of kinetics parameters recorded during walking.
  
  
  OBJECTIVE
  The aim of this study is the decrease of the inter-individual variability of the normal ground reaction force: F(z).
  
  
  METHODS
  The method tested consists in imposing a similar speed to the subjects during walking tests, then to class foot according to their function: loading or propulsive foot. A group of seven young adults walk at spontaneous speed (VSpon) for the first walking test then at similar speed (Vsim = N(Fr) x square root of (g x li); where N(Fr) is the Froud's number, g is the gravitational acceleration and li is the length of the lower limb) for the second walking test. Two forces platforms register the F(z) of two consecutive steps. The normal ground reaction force and the mean coefficient of variability are retained to test for speed (VSim and VSpon) and functional classification effects.
  
  
  RESULTS
  The CoV of F(z) decreases from 13% to 8% when the subjects walk at similar speed rather than at spontaneously chosen speed. The variability decreases by 1-1.5% when the data are classified according to functional criterion. The inter-individual variability of the F(z) significantly reduces when the tests are performed at similar speed and when the loading or propulsive factors are used for functional classification.
  
  
  CONCLUSIONS
  The coupling of the methods described must permit to the clinician to constitute a data base which, tainted of less variability, should make easier the detection of pathology affecting the ground reaction force.
authors.affiliation: Laboratoire d'études de la motricité humaine, FSSEP, 9, rue de l'université, 59790 Ronchin, France.
authors.forename: B
authors.initials: B
authors.lastname: Lefèvre
authors.forename: A
authors.initials: A
authors.lastname: Thévenon
authors.forename: P
authors.initials: P
authors.lastname: Moretto
mesh_terms: D000328:Adult; D001696:Biomechanical Phenomena; D005528:Foot / Q000502:physiology*; D006801:Humans; D008297:Male; D016138:Walking / Q000502:physiology*