Impact of foot-transmitted vibration on gait metrics, kinematics, and dynamic stability.

Transport operators face increased risks of injuries and falls while walking on a vibrating floor. No standards exist for human exposure to foot-transmitted vibration (FTV). In this study, twenty-one subjects walked on a treadmill constrained on a moving platform used to apply harmonic vibrations in four directions (mediolateral, anteroposterior, roll, and pitch) at four frequencies (0.5, 0.75, 1, and 1.5 Hz) with constant displacement (2 cm or 1°). The gait metrics, kinematic, and stability data were extracted in correspondence with the onset/offset of platform movement and when the steady-state of FTV was reached. Mediolateral vibration at the highest frequency was the most impactful condition, leading to the adoption of compensatory strategies to stabilize the center of mass closer to the floor and enlarge the base of support. These findings suggest that, from a normative perspective, a specific weighting curve is needed to assess human response to FTV while walking, since it varies as a function of vibration frequency and direction.