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An active trunk model for an improved calculation of stress acting on the lumbar spine during whole-body vibration

Project number: F 2070 Institution: Wölfel - Beratende Ingenieure GmbH & Co. KG Status: Completed Project

Description:

An anatomy-based model of the human developed by the TU-Darmstadt was improved and enlarged over a longer time period. A high level has been achieved with the research project 2028. A limitation of this model is caused by the modelling of the muscle response. Timing and size of the muscle forces which are triggered by the vibration influence have an influence on the stress acting on the spine. An adequate calculation of this active behaviour controlled by the nervous system in the mathematical model shall contribute to an improved judgment of the health risk caused by whole body vibration. The trunk muscles already reflected by the model shall be changed to actively controlled components. For the musculature an independent stature-dependent scaling shall be selectable.

The model shall reflect at least 2 different percentiles (m50 and m90 or m95) and postures (e.g. driving posture on commercial vehicles, bent forward) on hard or soft seat with or without use of back-rest. The electrical muscle activity (surface-EMG) derived in laboratory experiments should be used for validation of the force moments. Especially EMG-activity caused by stretching reflexes (without overlapping of other EMG generators) should be correlated with displacements of internal body-points (considering of reflex times and the electric mechanical latency). The calculation of internal strength courses shall be possible in any direction particularly in different levels of the spinal column under practically relevant conditions also during different postures under whole body vibration by using a program written in MatLab.

The calculation also must yield courses in the time domain for input signals with a practice-relevant dynamics in which nonlinear qualities and nonlinear behaviour have to be included. The active muscle force should be validated at least up to 5 Hz. A check of the model regarding torsion shall be carried out adapted for Perzentil m50 and, if necessary, for test subjects. If differences occur, the additional expenditure for the model should be taxed.

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