Asymmetric Kinematic Responses to Verbal Gait Instructions: Stooped Posture Induces Shorter Steps, but Not Vice Versa

Gait and posture are effective indicators of mood state. This relationship is bi-directional: improvements in gait and/or posture can improve mood, and vice versa. Previous studies have described spatiotemporal and kinematic features of gait and posture in individuals with depression or negative mood (e.g., stooped posture, shorter stride, lower speed) in parallel, without specifying whether these features are dependent of each other. However, some of the features may not be independent but secondary to other features. Here we show asymmetric kinematic responses to verbal instructions during overground walking in 20 healthy adults (10 females, 1 0 males), measured using a motion capture system with markers attached to the limbs and individual spinous processes. In the ‘stooped posture’ condition, the thoracic kyphosis is more pronounced (quasi-Cobb angle: $-37.3\pm 5.6^{\circ}$), as instructed, and the stride length $(1.22\pm 0.11\mathrm{m})$ and the speed $(1.16\pm 0.11\mathrm{m}/\mathrm{s})$ are lower than normal walking without any instructions $(-29.1\pm 5.6^{\circ}1.29\pm$ 0.12 $\mathrm{m}, 1.23\pm 0.13\mathrm{m}/\mathrm{s})$, even without specific instructions on stride parameters. In the ‘shorter stride’ condition, the stride is shorter $(0.96\pm 0.15\mathrm{m})$ as instructed and the speed is lower (0.92 $\pm 0.17\mathrm{m}/\mathrm{s})$, while the thoracic kyphosis is similar $(-28.8\pm 6.1^{\circ})$ to that of normal walking. Our observation suggests the unidirectional relationship that a shorter stride can occur secondary to a stooped posture but not vice versa. We suggest recognizing that some of gait features in negative mood may simply be secondary to other kinematic features.