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Abstract
In this study we describe an ambulatory system for estimation of spatio-temporal parameters
during long periods of walking. This original method based on wavelet analysis is
proposed to compute the values of temporal gait parameters from the angular velocity
of lower limbs. Based on a mechanical model, the medio-lateral rotation of the lower
limbs during stance and swing, the stride length and velocity are estimated by integration
of the angular velocity. Measurement's accuracy was assessed using as a criterion
standard the information provided by foot pressure sensors. To assess the accuracy
of the method on a broad range of performance for each gait parameter, we gathered
data from young and elderly subjects. No significant error was observed for toe-off
detection, while a slight systematic delay (10 ms on average) existed between heelstrike
obtained from gyroscopes and footswitch. There was no significant difference between
actual spatial parameters (stride length and velocity) and their estimated values.
Errors for velocity and stride length estimations were 0.06 m/s and 0.07 m, respectively.
This system is light, portable, inexpensive and does not provoke any discomfort to
subjects. It can be carried for long periods of time, thus providing new longitudinal
information such as stride-to-stride variability of gait. Several clinical applications
can be proposed such as outcome evaluation after total knee or hip replacement, external
prosthesis adjustment for amputees, monitoring of rehabilitation progress, gait analysis
in neurological diseases, and fall risk estimation in elderly.