Gait Stability Index Built by Kinematic Information Consistent With the Margin of Stability Along the Mediolateral Direction

Gait stability indices that can be easily measured and computed are required in both clinical and commercial applications. We established a novel gait stability index based on kinematic information that was substantially correlated with the margin of stability (MoS); a popular kinetic stability index. The novel index was computed using the time-series of triaxial velocities from the human body mass center. The partial least squares regression method was extended to time-series data and applied to the velocity series to compute the principal motions. These motions were elementary motions constructing the gait motions, and their magnitudes in each gait motion were correlated with the MoS. Gait data from 60 participants (30 males and 30 females; age: 67.6 ± 3.4 years (mean and standard deviation); height: 159.6 ± 7.6 cm; weight: 60.6 ± 9.3 kg) were analyzed. The combination of three principal motions exhibited a moderate correlation with the minimum MoS values in the mediolateral direction at
$r = 0.68$
, suggesting that the novel kinematic index can be used as an easy-to-access alternative to the MoS. The established kinematic index can be a substitute for the margin of stability.