Validation of a smartphone-based gait analysis focusing on waveform similarity

Abstract

Abstract Objective: Gait analysis using Inertial measurement units (IMUs) have gained attention owing to low economic and logistical constraints and obtaining spatiotemporal gait parameters with the same accuracy as that of conventional gait analysis. Most validation studies have focused on the agreement of spatiotemporal parameters calculated by integrating acceleration data with laboratory-based optical motion capture systems (OMCS), the gold standard of gait analysis. To legitimize analysis using acceleration waveforms, it is necessary to verify the parameters obtained from waveforms and their shapes; however, no research uses the similarity of waveform shape to validate the IMU gait analysis system. Thus, this study investigated the acceleration and angular velocity change waveforms obtained from the IMU as compared to a laboratory-based OMCS, the gold standard of gait analysis. Method: Ten walkers were recorded three times each, using an IMU and a laboratory-based OMCS. Three-axis angular velocities and acceleration waveforms were verified for similarity using the cross-correlation function (CCF) and dynamic time warping (DTW). Results: The derivative DTW distances between IMU and OMCS waveforms of the same gait were significantly smaller than those of the different gait groups in all directions. The acceleration waveforms toward gait, left-right direction, and vertical direction exhibited significant similarity, as did, angular velocities in pitch, yaw, and roll angular directions. Conclusion: Analysis using the acceleration pattern of the IMU can be legitimized without complicated signal processing for attitude estimation. These results can inform 3D motion analysis using the angular velocity of the pelvis.