The Effect of Sitting Posture on Human Movement in Whole-Body Vibration

The effect of sitting posture on human biomechanical response to whole-body vibration (WBV) was investigated in this work. Two popular sitting postures in the construction industry, standard back supported and bent forward (unsupported), were considered in this study (N = 4). A six-degree-of-freedom man-rated vibration platform, a twelve-camera Vicon motion capture system, three AMTI force plates, and four EMG sensors were used in the testing. The testing environment included the seat-pan, seatback, armrests, hand controls, and foot pedals. Each participant was exposed to multiple simulated ride files, including unidirectional swept sine motions (0.5 Hz-10 Hz) in the fore-aft and side-side directions, and random frequencies in multiple directions. The results demonstrate that subject responses are dependent on vibration direction and seated posture. During the fore-aft motion, subjects with unsupported forward postures experienced the greatest trunk motion at 3-5 Hz, whereas with the standard back-support posture, considerable increases in the seat-pan forces, pedal forces, seatback forces, and back muscle activation occurred at 6-8 Hz. During the random vibration trials, subjects experienced larger trunk motion with the forward posture, but greater neck flexion-extension motion with the standard supported posture. Keywords-3D motion;whole-body vibration; sitting; posture; motion captur; muscle activation; EMG