I am asked yet again how to find one's lactate threshold heart rate (LTHR) by doing a 30-minute time trial. I really don't understand what seems to be so difficult about this. All that's required is running (or riding) as hard as you can possibly go for 30 minutes ALL BY YOURSELF. It must be solo. Doing this as a part of a race or with training partners will change the outcome. Your number will be too high. If you want to do it with others or as a part of a race then you need to make it 60 minutes duration instead of 30.
One of cyclings simple mysteries...solved by Joe Friel