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.