title: Associations between short one-leg standing time and speed of sound of calcaneal bone in a general population: the Shimanami Health Promoting Program (J-SHIPP) study.
abstract: OBJECTIVE
  Loss of bone mass is a major cause of fracture in the elderly. One-leg standing (OLS) time has been postulated to be predictive of reduced bone mass. Here, we conducted a cross-sectional study to clarify whether OLS time measurements are associated with the speed of sound (SOS) of calcaneal bone independent of muscle mass in the lower extremity, a major confounding factor for the association, in a community-dwelling population of middle-aged to elderly subjects.
  
  
  METHODS
  The study subjects consisted of 770 apparently healthy middle-aged to elderly community-residents. Quantitative assessment of calcaneal bone was done using a quantitative ultrasound technique. OLS time with eyes open was measured with a maximum time of 60 s. Femoral muscle cross-sectional area (CSA) was measured from a computed tomography image.
  
  
  RESULTS
  Subjects who could not stand 60 s on one leg (n = 192) showed significantly lower SOS (1487 +/- 20, 1501 +/- 24 m/s, P < 0.001). In addition, femoral muscle CSA was positively associated with SOS (male, r = 0.148, P < 0.01; female, r = 0.204, P < 0.001). However, multiple regression analysis adjusted for age, sex and muscle CSA identified short OLS time less than 60 s as an independent determinant of SOS in both male (P < 0.001) and female (P < 0.05) subjects. OLS time was significantly associated with posturograph-measured mobility of the center of gravity. However, multiple regression analysis showed no significant correlation between balance impairment and SOS (P > 0.1).
  
  
  CONCLUSIONS
  OLS time less than 60 s was significantly associated with reduced SOS independent of age, sex and muscle mass in the lower extremity.
authors.affiliation: Department of Geriatric Medicine, Ehime University Graduate School of Medicine, Ehime University, Toon City, Japan.
authors.forename: Tomoko
authors.initials: T
authors.lastname: Kido
authors.forename: Yasuharu
authors.initials: Y
authors.lastname: Tabara
authors.forename: Michiya
authors.initials: M
authors.lastname: Igase
authors.forename: Eri
authors.initials: E
authors.lastname: Uetani
authors.forename: Namiko
authors.initials: N
authors.lastname: Ochi
authors.forename: Tetsuro
authors.initials: T
authors.lastname: Miki
authors.forename: Katsuhiko
authors.initials: K
authors.lastname: Kohara
mesh_terms: D000368:Aged; D001851:Bone Diseases, Metabolic / Q000000981:diagnostic imaging*; D002111:Calcaneus / Q000000981:diagnostic imaging*; D003430:Cross-Sectional Studies; D005080:Exercise Test; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D004856:Postural Balance; D012372:ROC Curve; D012307:Risk Factors; D014463:Ultrasonography