Strength Based Discomfort Model of Posture and Movement

The Lehrstuhl fur Ergonomie of the Technische Universitat Munchen is working on a generalized strength based discomfort model of posture and movements. By evaluating individual discomfort feelings of subjects regarding different postures, movements and different levels of force the first steps to find this function are realized. Different measuring machines permit the measuring of torques / force moments inside all joints of the human body. The individual feeling of discomfort is evaluated by using the CP50-scale for every fixed joint angle as well as every measured value. Discomfort is depending as well on the posture as on the level of force applied in a certain posture. Additionally the direction in which a certain force has to be applied influences discomfort feelings. Regarding different levels of force applied in a fixed posture the discomfort feeling increases linear with growing percentages of the maximal force/torque. Discomfort functions are calculated for every direction of every degree of freedom of the measured joints. By the analysis of movements and the definition of every discomfort value for every joint angle in combination with an applied percentage of the maximal torque it will be possible to validate a general discomfort model for human motion. The basis for this approach is the knowledge that the evaluation of discomfort for a complete movement is determined by the maximal discomfort felt in one joint or body part.