In the latest edition of the book, the info is spread across chapters 4 and 5. It starts with a discussion AeT:
- RPE of 3-4 out of 10
- lactate testing is most accurate way to determine
- gas exchange is 2nd best
- next is using rough estimate of 65% of HRmax
- another rough estimate is 20 to 40 bpm below your threshold HR
- an even simpler rough estimate is 30bpm below your threshold HR, which he thinks seems to work well for average fitness rider
Power and HR zone alignment:
- power and HR zones don’t always agree
- don’t be concerned, its common and expected
The functional AeT test:
- following a warmup, ride for 1-3 hours (based on duration of target event)
- ride at AeT HR, which to quote Friel “is LIKELY to occur at 20 to 40 beats per minute below your FTHR” (his words, my emphasis), or you can use FTHR minus 30bpm
There is a lot of wiggle room on those rough estimates.
HR is really personal, you need to figure out what works for you. This is what I’ve done for 5 years… my Friel zone2 HR is 131 to 142bpm (Coggan zone2 is 110-134bpm). My “all day HR” from doing 6-16 hour rides fall into that range. Eyeballing it, my average all-day is around 136-138bpm. After a season break I train by HR at 136-138bpm, and if feeling tired I’ll dial it down to 128-130bpm. After a 4 week block of endurance I’ll switch to training by power and my zone2 power usually results in zone2 HR which for zone2 workout at 70-72% FTP is 136-138bpm right in the middle of Friel but above Coggan (so I ignore Coggan HR zones).