DB suffering

Training Zones RPE

RPE Heart Rate (% Max) Description Talk Test

 

Level 1 < 80% Active recovery Able to have a chat
Level 2 80-89% Aerobic threshold Harder to breath but you can still talk if you concentrate
Level 3 90-94% Tempo Breathing is a challenge.  Talking is possible but only just
Level 4 95-99% Lactic threshold Breathing hard.  Conversation is nearly impossible
Level 5 >100 Aerobic capacity Can’t talk without gasping for air.  Just not possible for more than a few seconds

The photo show one triathlete who has been riding an Alpine pass at level 5 while his companion rarely got above level 2.