Jack Daniels Calculator wrote:
In a 2012 interview (in Norwegian), he stresses that volume is important (95mpw) is important
in contrast to "some claims that high intensity interval training can be replace it).
This is what I meant by the remark that they don't take 4*4 seriously.
But again, you may be getting lost in the definition of what exactly is "high intensity", when the term gets conflated with "Lactate Threshold" training, because historically in the United States, Lactate Threshold training is around the classic 4mmol point, which is typically around 91-92% HRmax. However, these guys are doing base 'Lactate Threshold repetitions' well below that intensity, if they are keeping their Lactate below 3mmol!
This is a major point of confusion on this topic, evidence by the many questions regarding how they can do multiple lactate threshold reps and sessions per day, and on successive days! The answer is because the intensity of those reps is lower than what is generally assumed to be Lactate Threshold Pace!
The caveat here is that 4 mmol is just an average across the entire population. The average is that 4 mmol is the threshold, and runners can hold that pace for around 1 hour.
In reality, sprinters are more fast-twitch, and produce a lot higher lactate values. 4 mmol might still be a jog for a sprinter, but he can reach 20+ mmol in a hard effort.
Top endurance runners (let's say 1500-Marathon) have a very high % of slow-twitch muscle fibers. They produce less lactate across the border, and their max lactate is substantially lower.
3 mmol for Ingebrigtsen might as well be the pace that he can sustain just 30 mins, or an hour, and not a pace that he could sustain for 3-4 hours like the average runner could. So for him, that's still roughly his threshold, and he is doing the repeats at the correct intensity for him.
If a 400/800 guy would do repeats at 3 mmol lactate, that's certainly too small, since he achieves 3 mmol at a pace that is still just easy/moderate for him, whereas for Jakob and other slow-twitchers it's already a strong effort.
Pace-wise, the Ingebrigtsen's seem to do a lot of their repeats around 10k-HM pace, which is in line with "CV training" and also the paces that runners have been training for decades, without labeling them "threshold" or "CV" etc..
This is an important observation, but it still only takes into account one side of the equation. Jakob is obviously heavy on ST fibers compared to the average runner, but he is a sub 3:30 guy and is almost certainly capable of running sub 13:00, which probably means he can clear far more than 4mmol of blood lactate before the running muscles start to experience acidosis. In studies by Canova, other sub 13:00 guys we're able to clear upwards of 8mmol of blood lactate steadily which means that they were able to run close to 5k pace without crossing the Lactate Threshold. The point I am trying to make here is that Jakob probably has a fair amount of FT fibers as well, but his Aerobic system is developed to the point that he can clear more than the universally excepted 4mmol.