title: Choice stepping response and transfer times: effects of age, fall risk, and secondary tasks.
abstract: BACKGROUND
  Deterioration with age of physiological components of balance control increases fall risk. Avoiding a fall can also require higher level cognitive processing to select correct motor and stepping responses. Here we investigate how a competing cognitive task and an obstacle to stepping affect the initiation and execution phases of choice stepping reaction times in young and older people.
  
  
  METHODS
  Three groups were studied: young persons (YOUNG: 23-40 years, n = 20), older persons with a low risk of falls (OLR: 75-86 years, n = 18), and older persons with a high risk of falls (OHR: 78-88 years, n = 22). Four conditions were examined: choice stepping, choice stepping + obstacle, choice stepping + working memory task, and choice stepping + working memory task + obstacle. Step response and transfer times were measured for each condition, in addition to hesitant stepping, contacts with the obstacle and errors made in the memory test.
  
  
  RESULTS
  Older participant groups had significantly longer response and transfer times than the young group had, and the OHR group had significantly longer response and transfer times than the OLR group had. There was a significant Group x Secondary task interaction for response time (F(2,215) = 12.6, p <.001). With the memory task, response time was minimally affected in the YOUNG (7% increase, p =.11) but was slowed significantly in the OLR fallers (42% increase, p <.001) and more so in the OHR fallers (48% increase, p <.001). The obstacle had a small but significant effect on response time (9.4%) and a larger effect on transfer time (43.3%), with no differences among the groups. Errors in stepping, performing the secondary task and contacting the obstacle increased with age and fall risk.
  
  
  CONCLUSIONS
  Compared with young people, older people, and more so those at risk of falling, have an impaired ability to initiate and execute quick, accurate voluntary steps, particularly in situations where attention is divided.
authors.affiliation: Prince of Wales Medical Research Institute, University of New South Wales, Sydney, Australia.
authors.forename: Rebecca J
authors.initials: RJ
authors.lastname: St George
authors.forename: Richard C
authors.initials: RC
authors.lastname: Fitzpatrick
authors.forename: Mark W
authors.initials: MW
authors.lastname: Rogers
authors.forename: Stephen R
authors.initials: SR
authors.lastname: Lord
mesh_terms: D000058:Accidental Falls / Q000517:prevention & control*; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000502:physiology*; D000704:Analysis of Variance; D001288:Attention / Q000502:physiology; D016009:Chi-Square Distribution; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D004856:Postural Balance / Q000502:physiology*; D012307:Risk Factors; D018709:Statistics, Nonparametric; D013647:Task Performance and Analysis; D013997:Time Factors; D016138:Walking / Q000502:physiology*