In office environments, workers spend the majority of their workday sitting in a static position behind a desk or around a meeting table. Prolonged sitting time and sedentary behavior have severe negative health effects. Through this explorative study, we studied how different postures can be stimulated during meetings. We designed PositionPeak: three pieces of furniture aimed at composing a 'dynamic meeting room', subtly encouraging participants to avoid static postures. We video-recorded 5 meetings (N=16) and coded the number of position changes per participant. Participants also filled out a pre-and post-questionnaire about their experience. Our findings show that PositionPeak triggers people to adopt a variety of postures. Participants on average experienced a more efficient meeting but reported physical discomfort with some objects. We discuss the influence of PositionPeak on the meetings' social dynamics, the acceptance of new conventions and design recommendations for new meeting facilities.