Acceleration root mean squares (RMS) of COM as a gait
stability parameter were estimated from the subject’s COM
position in anterior-posterior (AP) and medial-lateral (ML)
direction. The COM position was calculated as the weighted
sum of all body segments [18]. The stride-to-stride standard
deviations (SD) in acceleration RMS of COM were also
analyzed as the gait variability. These parameters were all
normalized by subjects’ gait velocity to avoid the confounding
effect of velocity on velocity dependent gait parameters [12].
(Unit of normalized acceleration RMS and its variability are
‘1/s’.)