Neck/Shoulder Muscle Fatigue of Military Vehicle Drivers Exposed to Whole-Body Vibration on Field Terrain Road

A driver of a military vehicle is exposed to whole-body vibration when driving in field terrain conditions, and the driver’s muscles become tired. Muscle fatigue occurs most strongly near both shoulders, which must be used to steer the vehicle in the target direction. The degree of a muscle fatigue is predicted to correlate with the exposure amount of the human body to vibration. In this study, the vibration driving a military vehicle on a field terrain test road was simulated using a 6-degree-of-freedom (DOF) exciter, and the muscle fatigue was analyzed by measuring electromyography (EMG) signals from subjects before and after the vibration exposure. Surface EMG (sEMG) measurements were taken at the deltoid and trapezius muscles of subjects for the muscle fatigue analysis. Before and after the vibration exposure, the Maximal Voluntary Contraction (MVC) state was determined. The change of the median frequency of the sEMG signal was measured in this state and analyzed. The output values of the sEMG signal at MVC decreased after the vibration exposure, suggesting reduced muscle activation. The change of the median frequency value after the vibration exposure was sharply reduced, which means that the muscles are fatigued more rapidly with the same load.