Sitting for prolonged periods of time impairs people’s health. Prior research has mainly investigated sitting behavior on an aggregate level, for example, by analyzing total sitting time per day. By contrast, taking a dynamic approach, here we conceptualize sitting behavior as a continuous chain of sit-to-stand and stand-to-sit transitions. We use multilevel time-to-event analysis to analyze the timing of these transitions. We analyze ∼30,000 objectively measured posture transitions from 156 people during work time. Results indicate that the temporal dynamics of sit-to-stand transitions differ from stand-to-sit transitions, and that people are quicker to switch postures later in the workday, and quicker to stand up after having been more active in the recent hours. We found no evidence for associations with physical fitness. Altogether, these findings provide insights into the origins of people’s stand-up and sit-down decisions, show that sitting behavior is fundamentally different from exercise behavior, and provide pointers for the development of interventions.

长时间坐着会损害人们的健康。先前的研究主要从总体上研究了就座行为，例如，通过分析每天的总就座时间。相比之下，采用动态方法，在这里我们将就座行为概念化为从坐到站和从站到站的转换的连续链。我们使用多级时间到事件分析来分析这些过渡的时间。我们分析了工作时间中156人的30,000次客观测量的姿势转变。结果表明，从坐到站过渡的时间动态不同于从站到站过渡的时间动态，并且人们在工作日晚些时候可以更快地转换姿势，并且在最近几个小时变得更加活跃之后可以更快地站起来。我们没有发现与身体健康相关的证据。共，