Acceleration of COM or trunk and its variability are
thought as important and more direct parameters of gait
stability [9, 10, 15, 23].This is proved by the results that our
middle-aged subjects showed a similar condition of body
acceleration as the older ones in ML direction, and
significantly differed from the young subjects. Our result is
also compatible with a notion that ML trunk acceleration and
its variability may play an active role in balance control during
elderly walking [12].