UMD is dead on. % of heart rate is pretty comparable. So, my max hr is 179 (resting below 50 bpm). Anytime I hit 93% I go anerobic and the clock starts ticking till I explode. So, the OP did 97% max hr for 1:21 ... yea that's a guaranteed popper and a giant effort. My biggest effort was 93% of max for 6:42 at the end of a 4 hour 34 min century.
I'm also a flaming numbers geek (engineer).