You've measured it wrong if you can't sustain it.

LAT HR is the rate at which you body disposes of Lactic at the same speed at which it creates it and is the optimal HR for a long time trial or breakaway to avoid muscle fatigue.

That you can't sustain it shows that your LAT HR is lower than 191.

this is where terminology becomes a problem

are we talking lactic threshold, as in the first point at which the rate of lactate clearance can't keep up with the rate of appearance? because to me, and the athletes I coach, that is lactate threshold.

the point where you hit anaerobic threshold, ie 4Mm, ie OBLA, ie the point where you go completely anaerobic - to me that is anaerobic threshold

i believe in north america it's called lactate threshold....

The word mostly use in litature is MLSS (maximum lactate steady state).

In the 80s they thought that it was at 4mmol/l lactate but that is not true.The lactate concentration is different for everybody on their MLSS.

What do you mean by completely anaerobic and anaerobic threshold? Anaerobic threshold is just a wrong word to describe the MLSS. And completely anaerobic do you mean maximum anaerobic? That's just your maximum while sprinting.