Detection and assessment of movements of the upper limbs

Status:

completed 06/2001

Aims:

Besides the spine, the upper limbs are most affected by muscolo-skeletal disorders and diseases. Repetitive strain, static strain, unfavourable body postures and movements, hand-arm vibration as well as the lifting and carrying of heavy loads are considered to be risk factors that may lead to the development of such injuries. Among these, the factor "unfavourable movements" appears to play a particular role. In order to improve the working conditions, i.e. take efficient preventive action at the concerned workplaces, a measuring system is needed which registers the relevant body movements. The stored posture data must then be converted into load characteristics such as to allow for an assessment of the health risk. The measuring system must also be designed for long-term use under various workplace conditions.

Activities/Methods:

Existing methods used to measure and analyse body postures and movements of the upper limbs were identified and investigated in view of their suitability for efficient long-term measurements at non-stationary workplaces. None of the available measuring systems meeting the defined requirements, a prototype of a new system was developed and tested. A mechanical construction, devised by the BIA, helps to position and fix the necessary sensors (potentiometers) at the joints. The measured angle data are stored in a memory unit worn on the back; they are thus immediately accessible for further processing. The system allows for the person-related, mobile registration of all movements of the upper limbs for a longer period of time. The following movements are registered: shoulder blade (front/back, lifting/lowering), shoulder (torsion, lifting/lowering, bending/stretching), elbow (bending/stretching), forearm (turning inwards/outwards), wrist (bending/stretching, bending sidewards). The further treatment of the measurement readings is done by use of a specially devised software at a stationary personal computer. This software allows for the measurement data to be presented in the form of angle/time curves or angle velocity/time curves of all types of joint movements; in addition, it is also possible to have a three-dimensional animated presentation in the form of a line-drawing. A further option enables the assessment of motion data on the basis of biomechnical and neurophysiological criteria, which are part of the software.

Results:

The result of the project is a serviceable prototype of the measurement system by means of which important mechanical risk factors for the shoulder/arm system can be quantified. These factors are specifically: work involving static joint posture, work involving a joint posture outside the neutral joint positions, work involving extreme joint positions, and repetitive activity. The measurement system is currently being put into practical use in projects, for example for measurement of shoulder-arm loading at sewing workplaces.

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