No where in my post did I say lactate causes fatigue.
Lactate is produced at every exertion, but to a varying degree.
Let me make it simple... MLSS can be defined as the fastest speed at which lactate does not increase to any significant degree over a long period of time. This is said to happen b/c lactate production=lactate elimination. Let's break it down, We have Joe run 30minutes at a specific pace and take lactate samples throughout. There will be an initial rise once Joe starts but then it will level off. At a slower pace it may look like this:
6 minute pace- reading at..
resting-.8
5min-1.4
10min-1.5
....30min-1.5ish
No increase from 10min to 30min, or at most a very very slight increase of .1.
Joe does the same test over and over again (fresh each time) at increasing speeds. At 5:45 pace there is still no increase from 10 to 30min. At 5:40 pace, sitll no increase. At 5:30 pace still no increase from 10 to 30min even though the lactate may be a bit higher throughout and look like this:
5:30 pace- reading at..
resting-.8
5min-2.5
10min-2.8
....30min-2.8ish.
but the key is no or very little increase from 10 to 30min because during this time lactate is being produced at the same rate as it's being eliminated. Now we do the test again and at 5:25 pace and the results are this:
5:25- reading at..
resting-.8
5min-2.5
10min-2.8
....30min-4.0ish.
uh oh, an increase, that means lactate production is no longer equal to lactate elimination.
And so you crossed your MLSS...the fastest pace at which lactate does not rise once at a steady state... So your MLSS is some where between 5:26-5:30 pace.
You do not need lactate to cause fatigue to have a MLSS.
And don't tell me these results would never happen because I've seen them documented and I've performed lactate tests like those above myself.
You say I represent the fallacy of lactate, but you represent someone taking data and forgetting real world application. Just because lactate does not directly cause fatigue does not mean LT or lactate is not useful. IF LT corresponds to the fastest pace at which you can run without lowering your blood pH or blood lactate or hydrogen ions or whatever you think causes fatigue, then it is a useful pace because for some strange reason all of those things seem to act simultaneously and correspond to one another (i.e. an increase in hydrogen ions occurs at the same time as an increase in lactate occurs!)
So for training purposes, it does not matter so much that lactate does not cause fatigue, but it matters that it coincides with it.