Interesting interview with Doc P ..mentions cortisol saliva testing to tell whether you are below maf or not.Also mentions running in ketosis saying we will be hearing more about it in the future.Didnt agree with his conclusion when he said dont go into ketosis because you need to eat fruit and pulses etc..way off mark doctor.I do understand that he is waiting to see what the long term effect is.

http://www.enduranceplanet.com/dr-phil-maffetone-the-power-of-aerobic-training-when-to-do-speed-work-clean-eating-for-athletes-strength-training-and-more/

Excellent podcast.

He pretty much lays out the program, and how flexible it is (as long as your MAF speed is imroving).

On a personal basis, I agree with him that ketosis is not a long-term place to hang out. Unless you can keep on top of the electrolyte flushing that continuously happens, problems can arise. They did with me. As soon as I got out of ketosis, the problems disappeared. I still continue to improve on low-carb (non-ketosis). The key is to get the body to use fat as fuel, and that can be done without being in ketosis. If you're giving mostly fat to eat, and training below MAF, that will happen.  Again, my personal experience, which one of these days you will get a full report.

--Jimmy