The connection between the built environment and physical activity has gained newfound attention. Plenty of research and several administrations highlight that how we plan our environments can nudge more people into active living. In Sweden, the act of planning in ways that promote physical activity has been on the agenda a few decades and many local administrations include this perspective in their spatial policies. This intrigues that spatial measures that promote physical activity should be well-known for Swedish planning officials, in addition to being noticeable in the built environment. However, there is often a considerable gap from accepted policies to applied practices as strategic spatial planning and especially the act of implementation are challenging. This thesis sheds light on how accepted spatial policies that promote physical activity have been considered and implemented in the built environment of Katrineholm. Results have been achieved by studying spatial policies, conducting in-depth interviews with planning officials and by analyzing the material thematically via the SPlaMI-framework. The results emphasize that the weakness of policy documents was a reoccurring challenge in the implementation-phase. Further, different actors, so called policy entrepreneurs, was pivotal for the outcomes and connected legal framework also played a crucial role. A surprising finding was that no cooperation between health experts and the planning department had been present, although these types of partnerships are highlighted in previous research. Finally, the absence of evaluation also presented a concern for further advancements.