Article

Everyday walking is often interrupted by obstacles and changes in the environment
that make gait a highly non-stationary process. This study introduces a novel
measure, termed the step stability index (SSI), to quantify stepping stability
under non-stationary walking conditions among older adults. This index is based
on the ensemble empirical mode decomposition method. We hypothesized that a
higher SSI would indicate a more stable gait pattern and could be used to assess
fall risk. Accelerometer-derived signals (vertical direction) were analyzed from
39 older adults with a history of 2 or more falls in the past year (i.e.,
fallers) and 42 older adults who reported no falls in the previous year (i.e.,
controls) under three walking conditions: baseline walk with and without a
harness, and obstacle course with a harness. In each condition, the subjects wore
a small, light-weight sensor (i.e., a 3 dimensional accelerometer) on their lower
back. The SSI was significantly higher (p </= 0.05) in the controls than in the
fallers in all three walking conditions. The SSI was significantly (p<0.0001)
lower for both the controls and the fallers during obstacle walking compared with
baseline walking. This finding is consistent with a less stable step pattern
during obstacle negotiation walking. The SSI was correlated with conventional
clinical measures of mobility and fall risk (the correlation coefficient, r,
ranged from 0.27 to 0.73, p<0.05). These initial findings suggest that the SSI,
an index based on the ensemble empirical mode decomposition, may be helpful for
quantifying gait stability and fall risk during the challenges of everyday
walking.
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Langue : ANGLAIS