Jane Fonda has been in the news recently and for years she worked out. She is now in need of a hip replacement and a knee replacement. I don't consider myself "old" (I am 51 and still do all the jumping around that you do). It hurts to run on pavement though. Any way my question is do you think that it is inevitable that all of us that do step and kick boxing will wear out our joints sooner than people that are sedentary or do low impact activity?