This is just it.
Most of the people suddenly d-riding for double-thresholds (that's double-riding, btw) weren't even running fast every day.
They are skipping straight from a hyperpolarized HARD day / EASY day program to double threshold work. FFS start with daily threshold work.
Not sure why this got 3 down votes. Marius was spreading out the boiling of threshold training over 4-5 days before cramming it all into 2.
He ran lots of 1k reps. On his old site and message boards, he wrote specifically that when he started, he was running 3:07 ish and it was a struggle to keep the lactate below 4mmol. But, after a few months, he was running 1000s well under 3 minutes and it was easy to keep the lactate within his desired range.
much of this training was done on a treadmill in order to further control the intensity.
he’s since written that later in his career, he experimented with sessions of higher volumes keeping the lactate even lower. I don’t have all of his articles memorized, but the general theme was that as he got stronger, he was running more volumes at lower lactates and then adopted the double threshold model.