Effects of walking speed and age on the directional stride regularity and gait variability in treadmill walking

In Inertial measurement unit (IMU) based gait analysis systems, the shoe-type sensor is not commonly used, unlike trunk attached sensors. The purpose of this study was to assess the directional Stride regularity (SR) and Gait variability (GV) of data from shoe-type IMU sensors during leveled treadmill walking. The other aim was to investigate the effects of walking speed and age on directional SR and GV in an attempt to find the directional preference associated with gait stability. The DynaStab TM (IMU based gait analysis system) including Smart Balance ® (shoe-type data logger) was used to collect normal gait data from forty-four subjects in their 20s (n = 20), 40s (n = 13), and 60s (n = 11). Four different walking speeds (3, 4, 5 and 6 km/h, respectively) on a treadmill were applied for one-minute of continuous leveled walking. Three linear accelerations and three angular velocities were measured with shoe-type IMU sensors. The SR (autocorrelation) and CV of ensemble data (coefficient of variation) on directional kinematics were calculated and compared with different walking speeds and ages. The results indicated that the lateral kinematics (mediolateral acceleration and yawing and rolling angular velocities) had lower stride regularity and higher gait variability than the anteroposterior and vertical kinematics across all walking speeds and ages. Significant interactions on the SRs and GVs from walking speed and age were found for only mediolateral acceleration and rolling angular velocity. Conclusively, the shoe-type IMU sensor system assessed directional SR and GV during walking conveniently. People should be careful with lateral kinematics since it is very sensitive to walking speed and age from the perspective of gait stability.