  Gait is an important biomarker of functional conditions and gait
characteristics can help us assessing health conditions and managing
progression of diseases. Most of the existing research study the gait in
controlled condition, such as clinical tests. In this paper, we study the gait
characteristics in free-living conditions in old adults and compare them with
that in controlled conditions, i.e., Timed Up and Go (TUG) test. 65 subjects
(12 patients with mobility impairment and 53 healthy controls) are recruited
from elderly nursing institutions. The video data are collected from them in
TUG test and free-living conditions and the 9 gait characteristics, including
gait speed, are extracted from the data. Two-sample tests and independence test
based on copula entropy are conducted on the extracted data to compare the
characteristics in two conditions. Comparison results show that gait
characteristics, such as gait speed, pace, speed variability, etc., in daily
life are different from that of in TUG test. In daily life, people tend to have
slow gait speed, smaller pace and speed variability, more frequent stride, and
smaller acceleration range than in TUG test. We also found that gait speed,
pace, and speed variability have stronger dependence with TUG score in the 3
conditions (TUG, daily life, and both) and that other 5 characteristics have
stronger dependence with TUG score in both condition than in each condition.
The comparison in this study suggests that TUG and daily life conditions are
complementary with each other, and that TUG test can be considered as
intervention on the movement state of human.
