There is the relationship between the physical activity of people and the city environment in which they live. This relationship is researched by project IPEN (International Physical Activity and the Environment Network). IPEN is an international interdisciplinary project. It studies the physical activity of citizens in the various structures of the town. There are many determinants that shape the citizen physical activity. The important factors are, for example, distances from home to shops and schools, the density of streets, land use in town etc.

Project IPEN has developed a methodology for analyzing city environment according to the physical activity of people. The main result of this methodology is a Walkability index. This index consists of four partial indexes: Connectivity index, Entropy index, FAR index (floor area ratio) and Household density index. Final Walkability index is the sum of partial indexes (where the weight of the Connectivity index is two times bigger than the weight of the other indexes).