Abstract. In this paper, we present three different ways of interrupting people to posture guidance. We developed an ergonomically adjustable office chair equipped with four sensors measuring the office worker's posture. It is important that users do some training after bad posture and be alerted of this; therefore, we implemented three different alert modalities (Graphical Feedback, Physical Feedback, and Vibrotactile Feedback), with the goal to find out which of the techniques is the most effective interruption modality without causing a huge disruption effect. To measure the task-performance, we conducted a formal user study. Our user study results show there are different effects on performance and disruptiveness caused by the three interruption techniques. While the vibrotactile feedback might have higher information awareness benefits at the beginning, it causes a huge intrusion side-effect. Thus, the physical feedback was rated less disruptive to the workflow as the other two feedback modalities.

A regular office chair was equipped with force transducers, which allow to monitor and to guide the sitting behavior of a person during an office working day. Only four force transducers are required to estimate characteristic parameters for quantifying the biomechanical effect of a certain sitting posture. Based on these parameters, which rely on a simple biomechnical model, a posture cost function was proposed for classification of the sitting posture. Since for posture guidance the posture control system has to be known, a simple approach for identification of the controller parameters is proposed. A framework for designing effective exercises is presented and allows to assess different exercises for improving the person's sitting behavior. The proposed sensor concept of the chair as well the proposed biomechanical model are evaluated by means of laboratory experiments.

A bed was equipped with four force transducers so that the location of the Center Of Mass (COM) can be computed, when the bed contains a person. The computation of the COM and its alterations in combination with the sum of all measured forces allows to compute the person's position in bed, an activity level, the resulting body weight and the corresponding weight change rate over time (overnight and long-term) as well as simply to determine whether the person is in the bed or not. The results of several overnight measurement experiments show, that the person's position in the bed (central, left, right) can be correctly detected, the proposed activity level is a promising indicator for the sleep-activity and furthermore the initial body weight as well as the nightly weight change rate can be determined.