Evaluation of the changes of gait stability on the treadmill due to treadmill velocity changes by means of time-frequency analysis

Abstract eng:
The frequency analysis enables the determination of changes of the COP trajectories during gait by means of detection of constantly repeated fragments. The time-frequency analysis was used in the conducted tests in order to assess the stability of gait on the treadmill. A group of 32 subjects participated in the tests at the age of 23(SD 1.8). The course of testing encompassed gait on the treadmill for 120 s. Initial velocity equalled V1=3.2 km/h for 60 s, then the treadmill accelerated by 25% to 4 km/h for subsequent 60 s. On the basis of the recorded distribution of pressure exerted on the ground and a software programme dedicated to treadmills, the following kinematic values were determined: cadence, stride time, stride length, step width for each examined group of participants and the COP position for the ML and AP directions. Using Matlab software programme, the researchers examined time-frequency dependencies and defined time-frequency periodograms for the ML and AP directions of the COP motions. In order to conduct a quantitative assessment of results, PSD coefficients were determined. The results indicate statistically significant changes in kinematic parameters except for the step width. The COP trajectories show the appearance of additional components indicating the change of gait stability. The changes of a method of body balancing and at the same time a way of the COP displacement during gait were confirmed by the analysis of the harmonic amplitudes. The conclusions show that the time-frequency analysis made it possible to determine changes in stability during the whole investigation on the grounds of the COP measurements. This methodology may be used to assess progress of the therapy of patients with balance instability.

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