title: Sex differences in the postural sway characteristics of young and elderly subjects during quiet natural standing.
abstract: OBJECTIVE
  It has been reported that the fall incidence in women is much higher than men and that fallers have worse postural balance performance than non-fallers. However, it is controversial whether any sex difference in postural balance performance exists. The purpose of this study was to investigate the effects of sex and age and their interactions in balance performance during quiet standing with natural stance width.
  
  
  METHODS
  Sixty-three elderly subjects (aged 65-86 years) and 66 young subjects (aged 18-26 years) performed quiet standing with self-selected natural feet distance on a force plate. Four analysis variables - mean distance, mean velocity, 95% power frequency and total power - were derived from the center of pressure (COP) and they were evaluated both in anteroposterior and mediolateral directions.
  
  
  RESULTS
  In anteroposterior direction, no sex effect and interaction existed, however, all variables except mean distance showed significant age effects (P < 0.01). In contrast, mediolateral direction variables showed significant sex effect where women had greater but less frequent COP movement than men (P < 0.01). Interactions of age and sex were also significant in mediolateral direction, where age-related changes were significant only in women so that sex differences (faster COP movement with more total power in women than men) existed only in the elderly (P < 0.01) but not in the young.
  
  
  CONCLUSIONS
  The sex difference in balance performance (some of which are significant only in the elderly) and the sex difference in age-related change of balance performance were demonstrated in mediolateral direction. These sex differences may contribute to the sex difference in balance-related problems, such as falls.
authors.affiliation: School of Biomedical Engineering, Konkuk University, Choonju, Korea.
authors.forename: Ji-Won
authors.initials: JW
authors.lastname: Kim
authors.forename: Gwang-Moon
authors.initials: GM
authors.lastname: Eom
authors.forename: Chul-Seung
authors.initials: CS
authors.lastname: Kim
authors.forename: Da-Hye
authors.initials: DH
authors.lastname: Kim
authors.forename: Jae-Ho
authors.initials: JH
authors.lastname: Lee
authors.forename: Byung Kyu
authors.initials: BK
authors.lastname: Park
authors.forename: Junghwa
authors.initials: J
authors.lastname: Hong
mesh_terms: D000328:Adult; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D006801:Humans; D008297:Male; D004856:Postural Balance; D011597:Psychomotor Performance; D012737:Sex Factors; D055815:Young Adult