The balance control system of a group of healthy and fit, young and el
derly subjects was studied during the initiation of stepping in one of
three directions: forward, sideways, and backwards in response to a l
ight cue. The performance of these movements requires shifting support
from two to one foot, moving the centre of mass outside the initial b
ase of support and creating a new support configuration. By recording
and analysing the vertical ground reaction force beneath the subject's
stepping foot, we were able to examine the two phases prior to limb l
ift-off for stepping: reaction time and weight transfer time. Both rea
ction time and weight transfer time increased with age: The elderly su
bjects had a proportionately larger increase in weight transfer time c
ompared to the reaction time. The peak force generated showed an age b
y stepping direction effect: the elderly had a significantly lower pea
k force for the forwards stepping compared to the younger subjects. Th
e larger increase in weight transfer results in a slower stepping resp
onse. Since a stepping task is often recruited to avoid a fall, the in
crease in response execution time can have undesirable consequences.