In positions where the support surface has only been changed in the m-l direction, we would have expected that only [S.sub.m-l] would change, but not [S.sub.a-p].
To a certain extent, these findings contradict those who reported on the mutually independent a-p and m-l COP movements, which could point to the independence among ankle-, hip- or load/unload balance strategies (Winter, 1995; Winter et al., 2003).
The maximum oscillation amplitude, both in m-l and a-p directions, increased in accordance with the reduction in SSS.