Nothing. I have been taking it real slow since my last round of knee issues. I was doing the first 1/3, or at least what we call the first 1/3 and then I worked my way to 2/3 of the form but it was always high. For some reason this morning things went well, muscle memory kicked in, the postures went to the prope height and I just let if go all the way to the end. Before I stopped when the knees hurt and this morning they did not hurt