The size of the functional base of support decreases with age

Falls occur more often as we age. To identify people at risk of falling, balance analysis requires an
accurate base-of-support model. We previously developed a functional base-of-support (fBOS) model
for standing young adults and showed that its area is smaller than the footprint area. Our fBOS model
is a polygon that contains centre-of-pressure (COP) trajectories recorded as standing participants move
their COP in the largest possible loop while keeping their feet flat on the ground. Here we assess how
the size of the fBOS changes with age by comparing 38 younger (YA), 14 middle-aged (MA), and 34
older adults (OA). The fBOS area is smaller in older adults: OA area is 58% of the YA area (p < 0.001),
and 59% of the MA area (p = 0.001), with no difference between YA and MA. The reduction in fBOS
area among the OA is primarily caused by a reduction in the length of the fBOS. In addition, among
older adults smaller fBOS areas correlated with a lower score on the Short Physical Performance
Battery (τ =0.28, p = 0.04), a reduced walking speed (τ =0.25, p = 0.04), and a higher frailty level
(p = 0.09). So that others can extend our work, we have made our fBOS models available online.