Characteristic of Trunk Acceleration and Angular Velocity in Turning Movement in Post-Stroke Patients with High Risk of Falling

Although falls are a commonly occur in post-stroke patients during turning, the characteristics of trunk movement during turning in those at high-risk falling remains unclear. The aim of this study was to clarify the characteristics of trunk translational and rotational movements during turning in post-stroke patients with high-risk falling. Trunk acceleration and angular velocity were measured using the inertial measurement unit of iPhone in the Timed up and go test and compared among 13 high-risk falling post-stroke patients (Berg Balance Scale (BBS) < 45), 18 low-risk falling post-stroke patients (BBS ≥ 45) and 10 age-matched healthy controls. We examined the differences in the trunk movement during turning between groups and the relationships between BBS score and trunk movement. The high-risk group exhibited the longest completion time (χ2 = 31.21, p < 0.001) and the lowest maximum of trunk angular velocity about the vertical axis among groups (χ2 = 28.51, p < 0.001). Furthermore, the high-risk group showed a higher minimum (absolute value) of trunk angular velocity about the medio-lateral axis compared to the low-risk group (χ2 = 9.80, p = 0.007). The maximum of trunk angular velocity about vertical axis (r = 0.66, p < 0.001) and the minimum of trunk angular velocity about the medio-lateral axis (r = 0.51, p = 0.003) were significantly correlated with BBS score. We found that the post-stroke patients with high-risk falling exhibited the slower trunk rotation angular velocity and faster trunk flexion angular velocity during turning compared to low-risk groups. Our findings suggest that despite of decrease during turning speed due to poor balance control, post-stroke patients with high-risk falling exhibited a greater disturbance in the sagittal plane.