For office workers as much as much as 77% of time at work is spent in sedentary behaviour, increasing the risk of cardio vascular disease, cancer, weight gain, obesity and musculoskeletal pain. Given the amount of time spent at work, increasing opportunities for moderate to vigorous physical activity for office workers can not only reduce risk of disease but also actively contribute to better brain function and reduced anxiety at work. In this research we adopt an ecological approach to understanding opportunities for physical activity at work. Using 1373 Fitbit data points from two collocated office workers with identical job descriptions, we demonstrate that episodes of movement in the office are of very short or short duration. Results were less clear for sedentary behaviour because of the potential for spurious step counts and the fact that accelerometers cannot distinguish between sitting and standing. The paper shows the limitations and potential of data from Fitbit devices as a means of understanding the opportunities and constraints of the organisational and physical environment for physical activity at work for office workers.