Outdoor fitness consists of exercise undertaken outside a building for the purpose of improving physical fitness like calisthenis parks or other outdoor site. It contrasts with exercise undertaken inside a gym or health club for the same purpose. The activity may be undertaken in a park, in the wilderness, or other outdoor location or can be done also at home in the garden.. The popularity of outdoor fitness grew rapidly in the second-half of the twentieth century and grew as a commercial consumer market in the twenty-first century. Modern mobile applikations allow users to organise group training and training programs in an outdoor fitness environment.