Measurement of postures and action forces to determine the lumbar load of care-activities

Diseases at the muscle and skeleton systems are one of the most frequent causes for health-related absenteeism in the workplace. Vocational fields of activity shaped in handling heavy loads increase the risk of diseases related to the intervertebral discs , especially lumbar load during care activities with patient transfer. At the Leibniz Research Centre for Working Environment and Human Factors at the University of Dortmund (IfADo), in co-operation with the Statutory Accident and Health Insurance Institution for Health Services and Welfare Care (BGW), this research project was accomplished, in order to assess lumbar diseases with respect to occupational reasons a nd for the development of preventive procedures for the avoidance of lumbar spine's disease ..

The relevant factors, which add to lumbar load of a person, are posture and exerted forces (action forces). Therefore measuring systems were developed and tested, to quantify these sizes spatially and in a high time resolution.

To analyze the posture and the movements of the nursing personnel, several infrared markers were attached to relevant body parts e.g. wrist, hip etc. The markers' spatial localizations were recorded via an opto-electronic ”position sensor system”. Additionally the position of the nurse was registered by several video cameras. Applying a graphical animation system, the real postures of the nurse were reproduced in an iterative procedure combining the video and the opto-electronic data. The health-care worker's action forces transferred during patient-transfer were captured “indirectly“ with the help of newly developed devices to enable force measurements at bed, chair and floor. For example, a common hospital bed was equipped with an additional framework attached to the bedstead and connected to the bedspring frame via tri-axial force sensors at the four bed corners. In that way, nurse's forces applied to the patient during the transfer were recorded in all three components (vertical, forward, sideward), and the point of force application was derived from force distribution. With the data of postures and forces, the load characteristic values for the spine were computed with a three-dimensional dynamic multi-segmental biomechanical model.