title: Detecting and quantifying global instability during a dynamic task using kinetic and kinematic gait parameters.
abstract: OBJECTIVE
  Instability during gait can be identified in many different ways. Recent studies have suggested utilizing spatiotemporal parameters to detect instability during gait. Detecting instability using kinetic and kinematic gait parameters has not yet been examined fully. In addition, these studies have not yet identified measures that are capable of assessing the magnitude of instability. The objective of the present study was to identify kinetic and kinematic gait parameters that can best identify instability and quantify its magnitude.
  
  
  METHODS
  Ten healthy men underwent successive gait analysis testing under three controlled settings: (1) Stage 0 instability (control setting), (2) Stage 1 instability and (3) Stage 2 instability. The levels of instability were precisely applied with the use of a controlled perturbation device (AposTherapy System). Differences between all stages and between stages were identified using Friedman and Wilcoxon tests.
  
  
  RESULTS
  Stride-to-stride variability (STSV) in kinetic and kinematic measures increased significantly between stages 0 and 1 or between stages 0 and 2 for almost all parameters (all P<0.05). A significant increase between stage 0 and both stages 1 and 2 was found for knee flexion moment, knee varus moment, knee flexion angle and hip adduction angle. The increase between stages 1 and 2 was variable. Only the knee varus moment parameter showed a significant increase in STSV between stages 1 and 2 (P=0.026).
  
  
  CONCLUSIONS
  Almost all kinetic and kinematic gait parameters are sensitive to changes in global instability in a dynamic task. The most sensitive are parameters measured at the knee. Of these, STSV in knee varus moment can be used to quantify the magnitude of dynamic instability.
authors.affiliation: Biorobotics and Biomechanics Lab, Faculty of Mechanical Engineering, Technion-Israel Institute of Technology, Haifa, Israel. eytan.debbi@aya.yale.edu
authors.forename: Eytan M
authors.initials: EM
authors.lastname: Debbi
authors.forename: Alon
authors.initials: A
authors.lastname: Wolf
authors.forename: Amir
authors.initials: A
authors.lastname: Haim
mesh_terms: D000328:Adult; D000465:Algorithms; D003198:Computer Simulation; D005684:Gait / Q000502:physiology*; D006801:Humans; D008297:Male; D008954:Models, Biological; D004856:Postural Balance / Q000502:physiology*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013647:Task Performance and Analysis; D016138:Walking / Q000502:physiology*