I agree with the lack of protein causing the weakness. I was walking 30 minutes on day 5, could only walk 20 minutes the following day, and none the next. I was able to start on soy milk and protein supplements on day 8 and it has made a world of difference. I had surgery on 9/5 and today I walked 40 minutes, then spent 2 1/2 hours walking around a street fair. I also recommend asking the doctor about adding protein. I have read and re-read the instructions and seem to learn something new each time. I'm on full liquids and feel very strong, just hungry!!!