Hi Cathe, First of all, I hope you don't mind if I gush. You are my idol. I absolutely love you, and I am so excited to be writing to you. I am a 37 year old mother of three little boys, and I have been doing your workouts for years. You are so incredible. You are a true professional, who inspires and motivates. I have so much respect for you, because it is clear that you really care about helping people. So, thank you!!! Thank you! Thank you! Now, on to my question: I just received the four day split. I have done two of the workouts so far. I was wondering how you use the four day split. Is it okay to work those particular muscle groups only once per week? I do a lot of cross training, running, biking, your aerobics, light weights, heavy weights etc. etc. etc. I am so excited about the four day split, I can always use a change. Thank you so much for taking the time to help. Your are so incredible.