Jakob Ingebrigtsen is doing A LOT of so called threshold training, being the most important part of the based training. I think I have the info right that he does 4 workouts (2 double days) with 5x6 or 6x5 w 1min rest in the mornings at a little lower lactate of <2.5 (probably at the true 1h threshold pace), but in the two evenings, doing 1k reps at 2.40 (5k-10k) pace w/1min rest and 60-90s reps @2.30-2.35 (3k-5k) pace w/25-30s rest, and <3.5 in lactate.
The interesting is not what he does, but what kind of workouts this really is. The rep length is short to very short for being threshold as such. The lactate indicates it is not lactate suffer workout either. It touches on CV work and short-reps VO2max.
The muscle work is depending on the pace and not the lactate and it is definitally activating fast muscle fibres (type 2A) and conditioning the legs for more specific speed.
What kind of workouts are these?
I have used much longer rep times and shorter rest and than the pace is much more a true threshold workout. I have also lately focused on speed and shortened the reps similar to Jakob's shorter rep workouts. I have done 2min reps with 30s rest and yesterday 90-70s reps with 30s rest. The effort and the feeling in the legs is like a threshold feels like, but the speed is definately not 1h threshold. I manage to get a lot of fast running very cheap (as long as I am used to running like this).
In fact I have eased down the effort in threshold work lately since I have increased speedwork and strength. If I run continuously I can feal a clear shift in breathing some 5-6% slower than true threshold pace, from easy breathing to controlled, but more. I guess this is what is called ventilatory threshold meaning that the breathing starts to accelerate more than the increase in pace would indicate. I used this same breathing threshold feeling to control my easy threshold workouts. Yesterday I did 70-90s reps. Feeling is like continuous running 5-6% slower than true threshold pace, but I hit paces 3% FASTER than true threshold. At the end I let go and hit my full threshold effort and run 4% even faster, meaning that I ran 7% faster than true threshold pace, meaning @ or faster than 5k pace.
I of course like to reach those paces realtively easy, and I can do a lot of reps at the effort as well. But I do not know what kind of workouts this is in terms of more classic thinking of VO2 max, CV, etc. This is not problem, just being overly interested in if ohters can explain this. I do not think this is threshold training since the paces are higher, but in terms of effort it FEELS like threshold work