title: The influence of preparedness on rapid stepping in young and older adults.
abstract: OBJECTIVE
  To investigate the influence of age and preparation level on postural muscle activation and step completion time during a rapid step task.
  
  
  METHODS
  Postural muscle onset times (EMG) and ground reaction forces were recorded from healthy young (n = 20, age 21 +/- 3 years) and older (n = 25, age 71 +/- 5 years) female adults during a choice reaction-time stepping paradigm.
  
  
  METHODS
  Onset times of six trunk and hip muscles, reaction time and components of the step (weight shift time, step time and task time) were recorded.
  
  
  RESULTS
  Muscle activation was delayed and movement time was lengthened in both young and older adults when poorly prepared for a stepping task. While reduced preparation did not influence older adults to a greater extent than young adults, the slowest step response and completion time was evident in older adults when poorly prepared to move.
  
  
  CONCLUSIONS
  A late postural response when poorly prepared to move may be a contributing factor to an increased risk of overbalancing in older adults. Future assessment of and intervention to improve postural stability in older adults should be expanded to incorporate tasks performed at various levels of preparation.
authors.affiliation: Department of Physiotherapy, University of Queensland, St Lucia, Australia. s.brauer@shrs.uq.edu.au
authors.forename: Sandra G
authors.initials: SG
authors.lastname: Brauer
authors.forename: Yvonne R
authors.initials: YR
authors.lastname: Burns
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000502:physiology*; D005260:Female; D006801:Humans; D008124:Locomotion / Q000502:physiology*; D004856:Postural Balance / Q000502:physiology; D011187:Posture / Q000502:physiology*; D011597:Psychomotor Performance / Q000502:physiology*; D011930:Reaction Time / Q000502:physiology*; D013647:Task Performance and Analysis