I dont think its too bad when you do it rarely either. Not at all would be ideal but hey I'm not perfect. I have to try body balance! I have been doing Body attack for ages and am still doing that once a week but it does get my heart rate up a little high I think (140 bpm) and I can no longer do all the 'high knees' running so I am hiding at the back of the class. Might give body balance a go..