About the link stating that 3 minutes all out effort won't disturb zone 2, that study is probably totally invalid for the majority of the population.

That study was specifically done with "trained athletes", for the rest of us, i.e. 99% of the population, the main effect of a 3 minutes long "all out effort" could just be an heart attack. Would they remain in zone 2 in this case...

You can't ignore that high-power and high-endurance athletes exhibit a distinct metabolic profile that reflects unusual steroid biosynthesis, fatty acid metabolism, oxidative stress, etc... the Reason for their performances, not just their training.

So... just a word of caution to those who prefer to use their brain than parroting anything they find on the internet!