Intraspinal forces and health risk caused by whole-body vibration—Predictions for European drivers and different field conditions

The extent of intraspinal forces under whole-body vibration (WBV) depends on several factors like multiple excitations of different body parts, stature and posture. The effects of these forces are determined by individual tolerances. Hence, there is no direct and simple relationship between WBV and health risk of the lumbar spine. The current evaluation methods with respect to health cover only part of the WBV input to the human body and do not consider all associated factors. A set of 50 finite element (FE) models was developed, based on human anatomy and adapted to different typical postures of European drivers and their anthropometric parameters. Three-dimensional matrices of transfer functions simulate these models and permit a practicable routine computation by a Matlab program with graphical user interface to predict intraspinal compressive and shear forces caused by WBV-input in x-, y- and z-directions at the seat, backrest, feet and hands, measured on mobile machinery. The effects of posture and stature on predicted WBV-related internal loads are demonstrated, for example, of numerous WBV-measurements under field conditions. The predicted static and vibration-related peak-to-peak dynamic compressive forces are processed with a method of risk assessment based on cumulative fatigue failure and implemented as a Matlab-program. The resulting risk factors of the new assessment method are compared with existing evaluation procedures of ISO 2631-1 and ISO 2631-5. They reveal significant differences.