Yesterday I had a stress test for my heart and had to run/walk on a treadmill for about 5 minutes. Well today I can barelly move. My legs, back, knee, and ankles hurt so bad I cannot sleep and I am extremely fatigued. My question is if exercise is good for us, then why am I feeling so horrable. I know you have to build up to exercise, but I was only on the treadmil for about 5 minutes. I only walked until the last minute and it was increased to a brisk walk.