+1
Listen to TL! He knows what he is talking about (he is also running similar reps himself at least a good number of the 400m ones).
And consequently almost everyone else on this thread is wrong.
And it is the same when reading the many other threads on the subject. There is so much wrong and confused opinions.
A reliable source for the Ingebrigtsen training is the Norwegian professor Leif Inge Tjelta´s article “THREE NORWEGIAN BROTHERS ALL EUROPEAN 1500M CHAMPIONS: WHAT IS THE SECRETE?” FROM SEPTEMBER 2019. Link here.
The key information is found om page 4 under “Training frequency and intensity distribution” where it is stated that the TRESHOLD PACE is the pace they run in their 2000m and 3000m reps whereas reps between 1000m and 400m are run between 10,000m and 5000m pace. NOTE THAT THE INGEBRIGTSENS HAVE APPROVED THE ARTICLE AND SINCE THEY TRAIN UNDER THE SAME REGIMEN TODAY AS IN 2019 THIS ARTICLE SHOULD BE AS AUTHORITATIVE AS IT COULD BE.
I will add:
They are running the reps according to predetermined lactate numbers so the pace is whatever triggers this lactate number.