title: Contribution of accelerated body masses to able-bodied gait.
abstract: OBJECTIVE
  The objectives of this study were to demonstrate that data from a video-based system could be used to estimate the net effect of the external forces during gait, to determine the contribution of the trunk and upper and lower limbs using their accelerated body masses, and to test the hypothesis that the thigh mainly assumed lower limb propulsion during able-bodied locomotion.
  
  
  METHODS
  The gait of 16 able-bodied subjects was assessed using an eight-camera video-based system and two force plates. The right limb was the leading limb, and there were two trials per subject. Although data from all the body segments were used to answer the first two objectives, only right limb information was used to address the third objective.
  
  
  RESULTS
  Pearson's coefficients of correlation and root mean square errors were calculated to determine the difference between the curves obtained from the sum of the external forces and that of the accelerated masses. These were >0.85, and the mean root mean square error was <4 N. Analyses of variance were performed on the peak forces developed by the trunk and the upper and lower limbs along each axis. Tukey's posthoc tests (P < 0.05) revealed that the trunk was the principal contributor of external forces in the frontal and transverse planes, whereas the lower limbs were found to be more important in the plane of progression. Analyses of variance and Tukey's posthoc tests (P < 0.05) were performed on the peak forces developed by each segment of the right limb. In decreasing order, the thigh, shank, and foot displayed the highest mass-acceleration products in the right limb during gait.
  
  
  CONCLUSIONS
  A video-based system was able to determine the net effect of the external forces with the summation of the mass-acceleration products during able-bodied gait. The trunk and lower limbs were the dominant body segments responsible for the production of external forces during able-bodied gait, whereas the thighs contributed more to the ground reaction force than the foot and shank for forward progression in able-bodied gait.
authors.affiliation: Laboratoire d'Automatique et de Mécanique Industrielles et Humaines, Université de Valciennes-Le Mont Houy, Valiciennes, France.
authors.forename: Christophe
authors.initials: C
authors.lastname: Gillet
authors.forename: Jacques
authors.initials: J
authors.lastname: Duboy
authors.forename: Franck
authors.initials: F
authors.lastname: Barbier
authors.forename: Stéphane
authors.initials: S
authors.lastname: Armand
authors.forename: Ridha
authors.initials: R
authors.lastname: Jeddi
authors.forename: François-Xavier
authors.initials: FX
authors.lastname: Lepoutre
authors.forename: Paul
authors.initials: P
authors.lastname: Allard
mesh_terms: D000054:Acceleration; D000328:Adult; D001696:Biomechanical Phenomena; D005121:Extremities / Q000502:physiology; D005684:Gait / Q000502:physiology*; D006801:Humans; D008297:Male; D018482:Muscle, Skeletal / Q000502:physiology*; D014741:Video Recording; D016138:Walking / Q000502:physiology*