title: Older adults at high risk of falling need more time for anticipatory postural adjustment in the precrossing phase of obstacle negotiation.
abstract: BACKGROUND
  Obstacles are a common cause of falls among older adults. Anticipatory motor planning for obstacle negotiation must be completed during the precrossing phase in order to step over the obstacle safely. This cognitive load may affect anticipatory postural adjustments (APAs) in older adults at high risk of falling. This study explored the effect of obstacle negotiation on APA during gait initiation in older adults at high risk of falling.
  
  
  METHODS
  Seventy-six elderly volunteers (mean age: 80.5 [7.6 years]) from the community participated in this study. Participants performed gait initiation tasks from a starting position on a force platform under the following two conditions: (1) unobstructed (smooth walkway) and (2) obstructed (walkway with an obstacle placed at 1 m from the initial position). The reaction and APA phases were measured from the data of center of pressure. Each participant was categorized as a high-risk or a low-risk individual according to the presence or absence of a fall experience within the past year.
  
  
  RESULTS
  High-risk participants had significantly longer APA phases than low-risk participants under the obstructed condition even though there was no significant difference between groups under the unobstructed condition. Reaction phase was not significantly different between groups in either the unobstructed or the obstructed condition.
  
  
  CONCLUSIONS
  Motor performance deterioration occurred in high-risk participants in the beginning of the precrossing phase of obstacle negotiation. A slow and inefficient APA at the precrossing phase of obstacle negotiation might be one of the causes of accidental falls.
authors.affiliation: Department of Physical Therapy, Human Health Sciences, Graduate School of Medicine, Kyoto University, 53 Kawahara-cho, Shogoin, Sakyo-ku, Kyoto, Japan. k.uemura@kw7.ecs.kyoto-u.ac.jp
authors.forename: Kazuki
authors.initials: K
authors.lastname: Uemura
authors.forename: Minoru
authors.initials: M
authors.lastname: Yamada
authors.forename: Koutatsu
authors.initials: K
authors.lastname: Nagai
authors.forename: Noriaki
authors.initials: N
authors.lastname: Ichihashi
mesh_terms: D000058:Accidental Falls / Q000517:prevention & control*; D000222:Adaptation, Physiological; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000502:physiology*; D003071:Cognition; D005260:Female; D005684:Gait; D006801:Humans; D008297:Male; D004856:Postural Balance; D011930:Reaction Time; D018570:Risk Assessment; D013997:Time Factors; D016138:Walking / Q000502:physiology*