title: [Influence of speed variation and age on the intrasubject variability of ground reaction forces and spatiotemporal parameters of children's normal gait].
abstract: OBJECTIVE
  To assess the effect of age and speed on the variability of ground reaction forces (GRF) and stride parameters of gait in normal children.
  
  
  METHODS
  Forty-seven children aged 4-10 years were split into three age groups. Each child walked at three constant speeds on a treadmill. Thirty consecutive steps of each leg were recorded. For each child, the mean parameters of the 30 steps were calculated. The mean parameter of each child was taken to calculate the mean parameters of the group. The variability was evaluated by the coefficient of variation (CV). The influence of both age and speed on the variability was examined with a to-way analysis of variance.
  
  
  RESULTS
  The cross effect of age and speed on the variability was not significant. The variability of the parameters decreased significantly with age between 4 and 8 years. The variability of vertical forces increased significantly with speed (between 2.7 and 4.5 km/h), while the variability of antero-posterior forces, the stride and the stance decreased between 2.7 and 3.6 km/h. However, the variability of double stance was not influenced by walking speed between 2.7 and 4.5 km/h. Except the time of production of the vertical force of propulsion (Tz3), the variability of temporal vertical parameters decreased significantly with speed between 2.7 and 4.5 km/h and the variability of temporal antero-posterior parameters decreased significantly between 2.7 and 3.6 km/h.
  
  
  CONCLUSIONS
  The variability of the GRF and spatio-temporal parameters in children was influenced by age between 4 and 8 years old and by speed between 2.7 and 3.6 km/h. Moreover, the effect of age on the GRF persists up to 8 years. The variabilities of the time of production of the antero-posterior force of propulsion (Ty2) and stance duration were lower than the variabilities of the others parameters. These two variables could be the most reliable parameters when assessing gait in children aged 4-10 years, walking at speeds between 2.7 and 4.5 km/h.
authors.affiliation: Equipe d'accueil EA E2S 3062, laboratoire de physiologie et physiopathologie de l'exercice et du handicap, Saint-Etienne, France.
authors.forename: M
authors.initials: M
authors.lastname: Diop
authors.forename: A
authors.initials: A
authors.lastname: Rahmani
authors.forename: P
authors.initials: P
authors.lastname: Calmels
authors.forename: V
authors.initials: V
authors.lastname: Gautheron
authors.forename: A
authors.initials: A
authors.lastname: Belli
authors.forename: A
authors.initials: A
authors.lastname: Geyssant
authors.forename: J
authors.initials: J
authors.lastname: Cottalorda
mesh_terms: D000367:Age Factors; D001696:Biomechanical Phenomena; D002648:Child; D002675:Child, Preschool; D005080:Exercise Test; D005260:Female; D005684:Gait; D006801:Humans; D008297:Male; D015203:Reproducibility of Results; D012737:Sex Factors; D013997:Time Factors