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

Aim: 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). Conclusion: OLS time less than 60 s was significantly associated with reduced SOS independent of age, sex and muscle mass in the lower extremity.