I have honestly searched for this, and have not been able to find a definitive answer as to what your % of LTHR you should ride in when doing SST efforts?

One range I saw, was 89 - 100% of LTHR. However, I have seen others indicate that this was too hard.

If someone could help me with this, I would appreciate it greatly.

Thanks,
V Biker

When I do a long (50 min) SST interval at constant power my HR slowly rises from about 85% to about 95% of threshold HR.