title: Walking in an unstable environment: strategies used by transtibial amputees to prevent falling during gait.
abstract: OBJECTIVE
  To investigate which strategies transtibial amputees use to cope with challenges of gait stability and gait adaptability, and how these strategies differ from strategies used by able-bodied controls.
  
  
  METHODS
  Cross-sectional study.
  
  
  METHODS
  An instrumented treadmill mounted onto a 6°-of-freedom motion platform in combination with a virtual environment.
  
  
  METHODS
  Transtibial amputees (n=10) and able-bodied controls (n=9).
  
  
  METHODS
  Mediolateral (ML) translations of the walking surface were imposed to manipulate gait stability. To provoke an adaptive gait pattern, a gait adaptability task was used in which subjects had to hit virtual targets with markers guided by their knees.
  
  
  METHODS
  Walking speed, step length, step frequency, step width, and selected measures of gait stability (short-term Lyapunov exponents and backward and ML margins of stability [MoS]).
  
  
  RESULTS
  Amputees walked slower than able-bodied people, with a lower step frequency and wider steps. This resulted in a larger ML MoS but a smaller backward MoS for amputees. In response to the balance perturbation, both groups decreased step length and increased step frequency and step width. Walking speed did not change significantly in response to the perturbation. These adaptations induced an increase in ML and backward MoS. To perform the gait adaptability task, both groups decreased step length and increased step width, but did not change step frequency and walking speed. ML and backward MoS were maintained in both groups.
  
  
  CONCLUSIONS
  Transtibial amputees have the capacity to use the same strategies to deal with challenges of gait stability and adaptability, to the same extent as able-bodied people.
authors.affiliation: Research Institute MOVE, Faculty of Human Movement Sciences, VU University Amsterdam, Amsterdam, The Netherlands.
authors.forename: Laura
authors.initials: L
authors.lastname: Hak
authors.forename: Jaap H
authors.initials: JH
authors.lastname: van Dieën
authors.forename: Peter
authors.initials: P
authors.lastname: van der Wurff
authors.forename: Maarten R
authors.initials: MR
authors.lastname: Prins
authors.forename: Agali
authors.initials: A
authors.lastname: Mert
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Beek
authors.forename: Han
authors.initials: H
authors.lastname: Houdijk
mesh_terms: D000058:Accidental Falls / Q000517:prevention & control*; D000222:Adaptation, Physiological; D000223:Adaptation, Psychological; D000328:Adult; D000674:Amputees; D003430:Cross-Sectional Studies; D005260:Female; D005684:Gait; D006801:Humans; D008297:Male; D008875:Middle Aged; D004856:Postural Balance; D013499:Surface Properties; D016138:Walking
keywords: AP; Amputees; BW; BoS; CAREN; CoM; Computer Assisted Rehabilitation Environment; LASI; LDS; LPSI; ML; MoS; RASI; RPSI; Rehabilitation; VE; Walking; XCoM; anteroposterior; backward; base of support; center of mass; extrapolated center of mass; left anterior superior iliac spine; left posterior superior iliac spine; local dynamic stability; margins of stability; mediolateral; right anterior superior iliac spine; right posterior superior iliac spine; short-term Lyapunov exponent; virtual environment; λ(s-step)