Resumen:
This chapter deals with the application of informalisation theory to sports. More specifically, it explores the informalising and reformalising phases occurring in the development of jogging/running in the USA (1960–2000). A spiralling fashion of informalising and reformalising trends was observed in the changes of jogging/running during three different periods: 1st period (informalisation), during the 1960s and 1970s, constituting the first jogging explosion; 2nd period (early reformalisation), during the 1980s; and 3rd period (consolidated reformalisation), during the 1990s, constituting the second explosion of running.