Quote Originally Posted by Heisenberg View Post
Zones are divined from when I was coaching with Dr. San Milan and did his test (the LT test from hell that also pegs cho/fat burn rate), as well as continued self-testing afterwards using the old 20-minute method. Read here for a much better explanation of constant endurance training from the source: What is Lactate and Lactate Threshold | TrainingPeaks

Not saying it's a good training method to win races, but it keeps me fittish.
Thanks for taking some time to share! I need to focus on the tank since my aerobic engine is weak and weight is up. No winning races from my more fit days, so looking more for the fitness and sustained weight loss you mention. Long term high fitness would be icing on a cake I don't have baked(not my original saying) :-).