I am using an HRM to train for my first marathon. MY resting heart rate is high 50's and my max is around 200 based on actual readings. My average heart rate during long run training has been 177. The longest run I've done is only 12 miles. What is the theory/idea for a good heart rate setting as compared to your own max HR for marathon training? I don't want to lose weight or anything like that. I am trying to run this thing as quickly as I can without killing myself. Should I set a pace where my HR is down at 160 and just live with the pace??? Thoughts, suggestions, criticisms...?