KJ -
Great and informative series of posts!

I have one series of interelated questions. I understand the need to stimulate increases in MVO2, but with that comes the attendant thickening of the heart's walls and valves. If this protocol is not appropriate for someone (because of detrainedness) would that actually increase their cardiac risk factors (i.e. athlete's heart)? and If it isn't appropriate would they be better off focusing more on longer, slower efforts in Z1 and Z2 to improve cardiac capacity (Z1)/cardiac power (Z2) first?

Second - with maximal and supramaximal endurance efforts we're put into an hypoxic state. Hypoxia destroys mitochondrial density, no? understanding that mitochondrial density isn't the golden calf, but still very important to endurance generally, do you think it wise to apply the MVO2 protocol for someone who is not looking to improve their SSST score or glycolitic capacity, but endurance more generally?

My questions are about applicability and appropriateness of the protocol, not of its' efficacy or elegance. I think your work is nothing short of genius. The question at the root is "Who is MVO2 appropriate for, and who should look elsewhere, and why?"