Cathe, I absolutely love Butts & Guts!! I've been doing it once a week since February. However, after doing it 3 weeks ago, after the general soreness went away after a day or two, I was left with a deep ache right in the center of my left butt cheek that radiates down a little bit into my hamstring. I skipped 2 weeks of Butts & Guts and did Slow & Heavy legs w/ no ache/problems, but now last Friday 04/20 I did Butts & Guts again and the ache came back. It went away after 3-4 days so I tried it again today - - I did skip the hamstring exercises on the ball and step today - - but the ache is now back. I wonder if I am just over training or am I doing one or some of the exercises wrong? Any suggestions? I don't want to give up Butts & Guts, but I also don't want to injure myself. Thanks!!