  We investigated the effect of performing a mental arithmetic task with two
levels of difficulty on the regulation of centre of foot pressure (COP)
displacements during bipedal quiet standing in young healthy individuals. There
was also a control condition in which no concurrent task was required. A
space-time-domain analysis showed decreased COP displacements, along the
antero-posterior axis, when participants concurrently performed the most
difficult mental arithmetic task. Frequency-domain and stabilogram-diffusion
analyses further suggested these decreased COP displacements to be associated
with an increased stiffness and a reduction of the exploratory behaviours in
the short term, respectively.
