Is a permit or reservation absolutely necessary to train bootcamp in the park?
It depends on the Park District. In Chicago you need to have a permit to use any of the parks. You need to call your Park District and ask, they may even require you to have liability insurance before they consider to let you use any park. You may get away with out anyone finding out that you are using their park, but if they do they may ask you to leave and don’t go back until you have gone thru them. Good luck!