title: Effects of age, step direction, and reaction condition on the ability to step quickly.
abstract: BACKGROUND
  The ability to take a step quickly is important for balance maintenance during activities of daily living. The purpose of this study was to investigate the effects of age, reaction condition, and step direction on the ability to take a volitional step as fast as possible.
  
  
  METHODS
  The performance of a voluntary step task was measured in young adult (mean age 20, SD 0.9 years), young-old adult (mean age 67, SD 3.7 years), and old adult (mean age 78, SD 2.3 years) healthy female participants. Each participant stepped as fast as possible in eight directions in response to a visual cue in a simple or choice reaction time condition. The effects of age, reaction condition, and step direction and their interactions on the primary outcome variables of response time, step liftoff, and step landing time were examined.
  
  
  RESULTS
  The normal aging process progressively increased the response, liftoff, and landing times. The choice reaction time condition, compared to the simple, had significantly increased response, liftoff, and landing times. Step direction significantly affected the liftoff and landing times, with lateral, diagonal, and anterior and posterioir (A-P) times increasing, respectively.
  
  
  CONCLUSIONS
  We found substantial declines in the ability to step rapidly in healthy adults as age increased. When a decision was required regarding the step direction, the step performance also declined. Step direction also significantly affected step performance. The assessment of voluntary step performance, which may be an indicator of balance ability, should include dimensions of both direction and the choice condition.
authors.affiliation: Department of Mechanical Engineering, University of Kansas, Lawrence 66045-2234, USA. luchies@ku.edu
authors.forename: Carl W
authors.initials: CW
authors.lastname: Luchies
authors.forename: Jeff
authors.initials: J
authors.lastname: Schiffman
authors.forename: Lorie G
authors.initials: LG
authors.lastname: Richards
authors.forename: Matthew R
authors.initials: MR
authors.lastname: Thompson
authors.forename: Doug
authors.initials: D
authors.lastname: Bazuin
authors.forename: Alice J
authors.initials: AJ
authors.lastname: DeYoung
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000502:physiology*; D002755:Choice Behavior; D005260:Female; D006801:Humans; D008875:Middle Aged; D011930:Reaction Time; D013997:Time Factors; D016138:Walking