FUNCTIONAL BASE OF SUPPORT DECREASES WITH AGE

Background, Poor balance in older persons increases the risk of injuri ous falls during daily activities. Functional base of support (FBOS), the anterior-posterior proportion of foot length used in maximal susta ined forward and backward leaning, tests controlled center of mass mov ement, a component of balance required in daily activities. The purpos e of this study was to examine the relationship between FBOS and age a nd establish the reliability of this measure. Methods. Subjects were 1 13 community-dwelling men and women, ages 20 to 91. FBOS, measured on a force platform, is the difference between mean center of pressure lo cation during sustained forward and backward leaning, divided by foot length. Forward lean (FL), backward lean (BL), and average sway distan ce during normal standing (STAND SWAY) and while leaning (FBOS SWAY) w ere also measured. Results. Mean FBOS was .60 +/- .07 in subjects unde r age 60, and .42 +/- .12 in subjects 60 and older. FBOS remained cons tant in younger subjects; beyond age 60, FBOS declined about 16% per d ecade and was more variable. FL and BL also declined with age, remaini ng 66% and 34% of FBOS, respectively. STAND SWAY and FBOS SWAY were si gnificantly correlated with each other, but not with FBOS. Conclusions , FBOS is a reliable measure and is decreased on average in older pers ons. This decrease is not related to increased sway while standing or leaning. FBOS is a simple force platform test that has potential as a measure of change in this dimension of balance and as a predictor of f alls risk in older persons.